, I will be now studying those threads and topics 
Hi, I wanted to ask if anybody has build a tube frame for his Locost instead of the one that is in book, or where can I find some info about this.
Thank you
George
I made mine using the base as square tube and upper as round tube, plenty of pics in my archive.
the base is 1" square as I have a rivited ali floor so I figured this would be easier, saved a bit of weight I guess.
Regards Mark
try here.
http://www.locostbuilders.co.uk/viewthread.php?tid=17998
like this?
http://www.locostbuilders.co.uk/forum/7/viewthread.php?tid=154561
quote:
Originally posted by blakep82
like this?
http://www.locostbuilders.co.uk/forum/7/viewthread.php?tid=154561
Thank you very much , I will be now studying those threads and topics
quote:
Originally posted by Doctor Derek Doctors
[Personally i think its a much better way to build a car, with a much better result.
Not the old 'round is better than square' chestnut.
DDD, as a 'F1' engineer, you should know that, given the same wall thickness and OD or edge length, square will outperform round in the
numbers every day(more metal at the extremities, so greater second moment of area), except for weight/metre. Well, unless they've rewritten the
engineering texts in the last day or so.
If the round is sized on OD to give the same cross sectional area as the square, and same wall thickness, then the situation changes. To get the same
area as 25mm square, with 1.5 wall, then the round will be over 28mm(28.4), then the moments will be higher and the round better, but not by enough to
warrant all the extra work needed in the joints.
I've been through the exercise on cad, and the fea doesn't show enough of a gain to warrant all the pain of those fishmouths, and the
problems of attaching flat panels to the round.
Cheers,
Nev.
[Edited on 23/5/11 by Neville Jones]
quote:
Originally posted by Neville Jones
Not the old 'round is better than square' chestnut.
DDD, as a 'F1' engineer, you should know that, given the same wall thickness and OD or edge length, square will outperform round in the numbers every day(more metal at the extremities, so greater second moment of area), except for weight/metre. Well, unless they've rewritten the engineering texts in the last day or so.
If the round is sized on OD to give the same cross sectional area as the square, and same wall thickness, then the situation changes. To get the same area as 25mm square, with 1.5 wall, then the round will be over 28mm(28.4), then the moments will be higher and the round better, but not by enough to warrant all the extra work needed in the joints.
I've been through the exercise on cad, and the fea doesn't show enough of a gain to warrant all the pain of those fishmouths, and the problems of attaching flat panels to the round.
Cheers,
Nev.
[Edited on 23/5/11 by Neville Jones]
quote:
Originally posted by Doctor Derek Doctors
quote:
Originally posted by Neville Jones
Not the old 'round is better than square' chestnut.
DDD, as a 'F1' engineer, you should know that, given the same wall thickness and OD or edge length, square will outperform round in the numbers every day(more metal at the extremities, so greater second moment of area), except for weight/metre. Well, unless they've rewritten the engineering texts in the last day or so.
If the round is sized on OD to give the same cross sectional area as the square, and same wall thickness, then the situation changes. To get the same area as 25mm square, with 1.5 wall, then the round will be over 28mm(28.4), then the moments will be higher and the round better, but not by enough to warrant all the extra work needed in the joints.
I've been through the exercise on cad, and the fea doesn't show enough of a gain to warrant all the pain of those fishmouths, and the problems of attaching flat panels to the round.
Cheers,
Nev.
[Edited on 23/5/11 by Neville Jones]
Funny then that all serious race cars with steel space frames are made from round and not square tube then isn't it? I wonder why that is? Hmmmmmmmmmmmmmmmmmmmmmmmmm?
For a race car, the extra work is warranted.
Odd one that, we could assume that for a given weight round tube is far superior?
I think I pointed that out above, but not 'far'. Just abit
Anyway if you could be bothered to read what I wrote I suggested that for anything other than a 'serious track or race car' a round tube chassis may be overkill.... but then again reading that may have meant there was no need to drag up an argument that was settled over 50 years ago.
I don't know why people are so visceral about defending 1" 16SWG Box? it has its place for cheap fun cars but for serious kit, it is proven that 'pound for pound' a round tube chassis provides a superior result.
I think I said that as well.
For a roadgoing 7 type car, other than 'bragging rights', a round tube car is a lot of extra work for little percievable gain, if any.
And please, leave off the smart arse attitude. I'm a lot closer linked to what your work is supposed to be, than you may think.
Cheers,
Nev.
Doctor Derek Doctors - 24/5/11 at 12:23 PMquote:
Originally posted by Neville Jones
quote:
Originally posted by Doctor Derek Doctors
quote:
Originally posted by Neville Jones
Not the old 'round is better than square' chestnut.
DDD, as a 'F1' engineer, you should know that, given the same wall thickness and OD or edge length, square will outperform round in the numbers every day(more metal at the extremities, so greater second moment of area), except for weight/metre. Well, unless they've rewritten the engineering texts in the last day or so.
If the round is sized on OD to give the same cross sectional area as the square, and same wall thickness, then the situation changes. To get the same area as 25mm square, with 1.5 wall, then the round will be over 28mm(28.4), then the moments will be higher and the round better, but not by enough to warrant all the extra work needed in the joints.
I've been through the exercise on cad, and the fea doesn't show enough of a gain to warrant all the pain of those fishmouths, and the problems of attaching flat panels to the round.
Cheers,
Nev.
[Edited on 23/5/11 by Neville Jones]
Funny then that all serious race cars with steel space frames are made from round and not square tube then isn't it? I wonder why that is? Hmmmmmmmmmmmmmmmmmmmmmmmmm?
For a race car, the extra work is warranted.
Odd one that, we could assume that for a given weight round tube is far superior?
I think I pointed that out above, but not 'far'. Just abit
Anyway if you could be bothered to read what I wrote I suggested that for anything other than a 'serious track or race car' a round tube chassis may be overkill.... but then again reading that may have meant there was no need to drag up an argument that was settled over 50 years ago.
I don't know why people are so visceral about defending 1" 16SWG Box? it has its place for cheap fun cars but for serious kit, it is proven that 'pound for pound' a round tube chassis provides a superior result.
I think I said that as well.
For a roadgoing 7 type car, other than 'bragging rights', a round tube car is a lot of extra work for little percievable gain, if any.
And please, leave off the smart arse attitude. I'm a lot closer linked to what your work is supposed to be, than you may think.
Cheers,
Nev.
Smart arse attitude.... oh for petes sake stop being so defensive
Like I said, you didn't read my original comment about it being overkill for anything other than race cars and serious track cars and again you failed to acknowledge that part of my point.
Round tube is better as a structural element, it is however more difficult to work with.
The OP asked for information on building a tube frame chassis which was forthcoming, I don't know why you took that as some sort of personal insult and had to defend the honor of 16SWG box in a thread were that wasn't relevant.
Longerr - 24/5/11 at 02:41 PMSo what diameter and thickness of a tube I should use so it has any sence to do it instead of square tube. I want the car for racing
Doctor Derek Doctors - 24/5/11 at 03:38 PMquote:
Originally posted by Longerr
So what diameter and thickness of a tube I should use so it has any sence to do it instead of square tube. I want the car for racing
If its a race car then it should be a tube chassis, otherwise you will be comprimising the very base performance of the car.
1" 18swg Seamless Tube is a good material to start with for the frame, you may want to use some 16swg for more 'stressed' areas around things like the diff and engine mounts. On non structural parts you could use smaller tube like 3/4" 18swg.
If its a race car remember that your roll cage will be have to be made from MSA BluBook Compliant materials and to their design regs not from normal tube.
This is only the most very basic outline though, proper study should be done to get the answers that you need.
Neville Jones - 24/5/11 at 04:31 PMDDD, what diameter and thickness tube is your car built from?
What is the centre - centre distance of the top and bottom side tubes?
With those numbers, I can tell you how much weight you've saved, how much more flexible your chassis is, and how much higher stressed it is, verses a square tube chassis to the book.
Geez, as an 'F1' engineer, you should be able to quote all that chapter and verse!
For anyone building a 'book' chassis or similar, you need to use, as a minimum, 28.5mm diameterx1.5mm wall to have similar strengths and torsional stiffness as a 'Book' chassis built with 25mmx1.5mm square tube.
[1" 18swg Seamless Tube is a good material to start with for the frame, you may want to use some 16swg for more 'stressed' areas around things like the diff and engine mounts. On non structural parts you could use smaller tube like 3/4" 18swg. ]
Thinner tube will be more flexible, simple mechanics. It will be higher stressed, so therefore will have a much shorter life.
Every tube should be structural, otherwise it's redundant, and can be left out. Come on DDD, you should know that!!! Colin Chapman had that as his main motto.
[If its a race car then it should be a tube chassis, otherwise you will be comprimising the very base performance of the car.]
Utter BS!!! Round tube or square tube? Do your numbers before coming out with these unfounded statements. A square tube chassis can equal or better a round tube item every day of the week!!
The old time racecars were built with round tube, mainly because they used aircraft tehnologies of the time and thus chrome-moly tube, and it was only available in round. Still is as far as I know, but it's something I haven't searched out as I don't have a need. If they had the square available as it is today, I'm sure it would have been used when necessary.
The downside of chrome-moly, is that it needs to/should be heat treated in an oven over a period of days, after welding, to negate stress concentrations and HAZ failures. Obligatory in some countries before the chassis is allowed to race.
Now,DDD, before you jump up and down and make silly noises, go back to your first year engineering mechanics and structures notes,( you did do an engineering degree, didn't you?) and do your numbers. This stuff is just about my daily 'bread and butter', and I'm not too slim so I can't be far wrong, otherwise I'd starve and look like a catwalk model!
To those few 'proper' engineers who send me messages, please feel free to step in and be counted. ( Ex ships 'engineers' who got their degree(?) from Woolworths are exempted.
Remember, do your numbers before writing further. Your head is in the noose, and you're standing on a rickety three legged chair.
Cheers,
Nev.
littlefeller - 24/5/11 at 04:32 PMinteresting thread, ( square v round).
i can throw my opinion in too as i know about this. round tube is mathematically superior to square tube in space frame construction, however it is only as good as the joints, the joints on round tube have to be near perfect to be stronger than square profile. as most don’t have the tools to do this correctly then square is better. umm still hasn’t done any good
phelpsa - 24/5/11 at 04:58 PMhttp://www.roymech.co.uk/Useful_Tables/Sections/SHS_hf.html
http://www.roymech.co.uk/Useful_Tables/Sections/Cir_Sect.html
Compare 2nd moment of area.
Doctor Derek Doctors - 24/5/11 at 09:20 PMquote:
Originally posted by Neville Jones
DDD, what diameter and thickness tube is your car built from?
What is the centre - centre distance of the top and bottom side tubes?
With those numbers, I can tell you how much weight you've saved, how much more flexible your chassis is, and how much higher stressed it is, verses a square tube chassis to the book.
Geez, as an 'F1' engineer, you should be able to quote all that chapter and verse!
For anyone building a 'book' chassis or similar, you need to use, as a minimum, 28.5mm diameterx1.5mm wall to have similar strengths and torsional stiffness as a 'Book' chassis built with 25mmx1.5mm square tube.
[1" 18swg Seamless Tube is a good material to start with for the frame, you may want to use some 16swg for more 'stressed' areas around things like the diff and engine mounts. On non structural parts you could use smaller tube like 3/4" 18swg. ]
Thinner tube will be more flexible, simple mechanics. It will be higher stressed, so therefore will have a much shorter life.
Every tube should be structural, otherwise it's redundant, and can be left out. Come on DDD, you should know that!!! Colin Chapman had that as his main motto.
[If its a race car then it should be a tube chassis, otherwise you will be comprimising the very base performance of the car.]
Utter BS!!! Round tube or square tube? Do your numbers before coming out with these unfounded statements. A square tube chassis can equal or better a round tube item every day of the week!!
The old time racecars were built with round tube, mainly because they used aircraft tehnologies of the time and thus chrome-moly tube, and it was only available in round. Still is as far as I know, but it's something I haven't searched out as I don't have a need. If they had the square available as it is today, I'm sure it would have been used when necessary.
The downside of chrome-moly, is that it needs to/should be heat treated in an oven over a period of days, after welding, to negate stress concentrations and HAZ failures. Obligatory in some countries before the chassis is allowed to race.
Now,DDD, before you jump up and down and make silly noises, go back to your first year engineering mechanics and structures notes,( you did do an engineering degree, didn't you?) and do your numbers. This stuff is just about my daily 'bread and butter', and I'm not too slim so I can't be far wrong, otherwise I'd starve and look like a catwalk model!
To those few 'proper' engineers who send me messages, please feel free to step in and be counted. ( Ex ships 'engineers' who got their degree(?) from Woolworths are exempted.
Remember, do your numbers before writing further. Your head is in the noose, and you're standing on a rickety three legged chair.
Cheers,
Nev.
I love internet forums, the pure unadaulterated energy expended when people feel the need to defend something as inane as the shape of a piece of metal is brilliant. Like its going to change the opinion of the world or something.
As I said the the OP asked for detail on building a tube frame and somehow you managed to start an argument from nowhere that was irrelevant to the question.
Have fun and don't have a heart attack.
Edit: Just noticed you last line, brilliant! My head is in a noose on rickety chair.... you really are one for the melodrama aren't you. In actual fact I'm supping a cold beer and watching South Park having a little chuckle while enjoying life.
[Edited on 24/5/11 by Doctor Derek Doctors]
flibble - 24/5/11 at 09:29 PMquote:
Your head is in the noose, and you're standing on a rickety three legged chair.
Ahh, but are the three remaining legs round or square section, and which would be stronger?
Neville Jones - 25/5/11 at 10:50 AM[Edit: Just noticed you last line, brilliant! My head is in a noose on rickety chair.... you really are one for the melodrama aren't you. In actual fact I'm supping a cold beer and watching South Park having a little chuckle while enjoying life. ]
Another way of saying,'give a person enough rope and they'll hang themselves'.
More like got a hold of something in your trousers and imagining you're an engineer.
Make attempts at ridicule all you like, BUT...
Where are numbers to back up your broad ranging statements? Where????
Could it be that the numbers contradict your views? Could it be you don't even know how to work out the numbers?
Should be very straight forward for an 'F1 Engineer'......but that's where truth and reality part company, eh?
Cheers,
Nev.
phelpsa - 25/5/11 at 11:30 AMquote:
Originally posted by Neville Jones
Should be very straight forward for an 'F1 Engineer'......but that's where truth and reality part company, eh?
Well that would strictly depend on what team you're working for
What's all this bickering about being an F1 engineer about anyway?
Neville Jones - 25/5/11 at 11:33 AMBickering?
No, but the guy made a big noise a while ago about working in F1 as an engineer. As you can see, I have my doubts.
Should you not be studying for exams?
Cheers,
Nev.
phelpsa - 25/5/11 at 11:42 AMquote:
Originally posted by Neville Jones
Should you not be studying for exams?
Cheers,
Nev.
Point taken.
Over and out.
blakep82 - 25/5/11 at 11:44 AMremind me never to ask a question about whats stronger....
anyway, as to the person that originally asked this, I'm thinking they are both very similar in strength. each have pros and cons, and it probably not worth worrying about. use whichever you prefer.
now im wondering if the fishmouths/notches of round tube create a larger surface area for each weld, if that makes the chassis as a whole stronger vs square tube?
but for now i'm gonna sit back and see how this continues
Liam - 25/5/11 at 01:12 PMI agree with Neville (!!). For a given chassis design, substituting 1" square 16swg for 1" round 18swg will result in a significantly weaker and less stiff chassis, for a weight saving of no more than a few % of the total car weight. The stiffness of a spaceframe chassis arises primarily (ideally totally) from the axial stiffness (i.e. tension) of the members, which is proportional to the cross-sectional area - not from bending stiffness. To even get the strength and stiffness back, let alone improve on it, you have to maintain wall thickness and go up in OD as suggested, so the result for the same strength/stiffness is a near negligable weight saving of the complete car, and you've given yourself all the fabrication and attachment headaches! It's only remotely worth it if the opportunity it gives to use exotic material not available in square is taken, and even then, unless you're shaving 10ths off lap times there's barely any point. The perceived advantage arising from the larger second moment, and hence higher bending stiffness, should barely be of relevance either - the chassis members should not be under bending load anyway. And if there are unsupported tubes long enough that resistance to buckling under compression is a concern, it's the design that needs addressing and not the material section choice.
littlefeller - 25/5/11 at 04:14 PMquote:
Originally posted by flibble
quote:
Your head is in the noose, and you're standing on a rickety three legged chair.
Ahh, but are the three remaining legs round or square section, and which would be stronger?
compositepro - 26/5/11 at 01:39 PMthis is my first post here on this forum but ....big but.
Has anyone ever tried doing a monocoque?
welderman - 26/5/11 at 01:58 PMA little off topic, which ive just had a read of and it's quite funny in places.
Your head is in the noose, and you're standing on a rickety three legged chair.
Ahh, but are the three remaining legs round or square section, and which would be stronger?
But which is stronger (smell), Stinking Bishop or Stilton ?.
Peteff - 26/5/11 at 02:08 PMquote:
Originally posted by compositepro
this is my first post here on this forum but ....big but.
Has anyone ever tried doing a monocoque?
To keep in the spirit of the thread, who are you calling big but?
compositepro - 26/5/11 at 02:20 PMquote:
Originally posted by Peteff
quote:
Originally posted by compositepro
this is my first post here on this forum but ....big but.
Has anyone ever tried doing a monocoque?
To keep in the spirit of the thread, who are you calling big but?
Thanks Peteff I was thinking of a composite though.
alistairolsen - 26/5/11 at 03:11 PMOh dear, here we go!
Guarantee this is a more heated debate than tube geometry!
(personally, Id love to do one sometime!)
phelpsa - 26/5/11 at 04:17 PMquote:
Originally posted by compositepro
quote:
Originally posted by Peteff
quote:
Originally posted by compositepro
this is my first post here on this forum but ....big but.
Has anyone ever tried doing a monocoque?
To keep in the spirit of the thread, who are you calling big but?
Thanks Peteff I was thinking of a composite though.
Yes, look up Westfield FW400. Less than 400kgs with a car engine!
indykid - 26/5/11 at 04:23 PMWasn't volvosport working on a composite monocoque 7 many moons ago, or did I make that one up?
Steve Hignett - 26/5/11 at 04:34 PMquote:
Originally posted by alistairolsen
Oh dear, here we go!
Guarantee this is a more heated debate than tube geometry!
It should be an OK topic really, as a monocoque is different to what was discussed and laughed at previously.
Probably best to start a new topic though, if I were you, CompositesPro...
I'm (very very briefly) familiar with composites and know people who've done their own monocoques utilising a moped's (185 engine) engine and running gear at the back and 2 conventional wheels at the front.
Monocoques are a very good way to make a car (race car) in composites, but it would take a fair bit of re-reading about if I was to give my advice to someone else!
Neville Jones - 26/5/11 at 05:16 PMSomeone in the Southern Hemisphere does a composite chassis'd 7 clone.
Could be Birkin, or one of the NZ companies? Maybe Westfield Aus, Arrow?
Cheers,
Nev
blakep82 - 26/5/11 at 05:24 PMremember the guy on here years ago that was talking of doing a monocock chassis
Liam - 26/5/11 at 05:58 PMCock
Hee hee
compositepro - 26/5/11 at 06:41 PMhi guys thanks for the heads up on the cars with the chassis
I was going to comment on the tubular frames as I do have experience in that area but mostly I have been lurking and reading various forums trying to figure out where things lie in the self build world ...I like the exocar style!!! am i allowed to say that?
However with my love of even classic things with a modern twist the thing that did stand out was that there wasn't anything with a monocoque chassis and whilst I understand the cost implications of this type of construction it did puzzle me as the kit car fraternity seems to be an inventive bunch.I was looking for a starting point for a build and maybe the info youve provided will give me that.
I will start my own thread however as I didnt mean to hijack this one
thanks
Volvorsport - 26/5/11 at 07:27 PMi was.....
it got bastardized into something else
littlefeller - 26/5/11 at 08:45 PMhijack away, its getting intresting
Neville Jones - 27/5/11 at 11:34 AMA composite racecar 7 has been done a few times.
For the road, I wouldn't entertain the idea, as IVA asks you to go through very stringent specs, although these aren't made clear publicly.
It's part of the reason the RH's had so much trouble with their mono's, (along with the questionable build methods in places).
Cheers,
Nev.
Confused but excited. - 27/5/11 at 12:38 PMAll this is very interesting to a numpty like me (note my LCB name), but as DDD stated "On non structural parts you could use smaller tube like 3/4" 18swg."
This got me more confused. My question is; What parts of a locost/space frame type chassis are non-structural?
Or have I missed something?
This is not meant to be snide, so apologies to anyone who may think different. Just trying to expand my meagre knowledge.
littlefeller - 27/5/11 at 06:32 PMwhat exactly is iva requirement for chassis and how are they tested
[Edited on 27/5/11 by littlefeller]
v8kid - 27/5/11 at 06:45 PMquote:
Originally posted by Confused but excited.
All this is very interesting to a numpty like me (note my LCB name), but as DDD stated "On non structural parts you could use smaller tube like 3/4" 18swg."
This got me more confused. My question is; What parts of a locost/space frame type chassis are non-structural?
Or have I missed something?
This is not meant to be snide, so apologies to anyone who may think different. Just trying to expand my meagre knowledge.
The bits you hang other stuff off! Like seats, gearlever, steeringwheel, radiator, engine/box - that sort of stuff
BTW square v round it depends on how you are loading it, bending (loads of different planes), torsion, buckling, shear - cant think of any other modes offhand - the point is you have to know how the particular member is loaded before making a decision.
Great thread.
Cheers!
bikenuts - 27/5/11 at 07:55 PMJust to pop a couple more logs on the fire;
Round tube is more susceptible to damage and even a small dint reduces its strength dramatically.
Which way should you orient your square tube? It's almost always used with the flat side parallel to the ground but would rotating it 45 degrees give a stiffer structure? after all the second moment is greater in bending that way????
Bikenuts
compositepro - 27/5/11 at 08:43 PMI'm interested to know what problems people had with the monocoques .I do see a lot of fear on the various forums I've come across with home builds aluminium and carbon being the main ones but I can see the reasoning behind it when most are building from home.
Having done a fair bit of calculating before embarking on this including the square versus round it is pretty easy to build a chassis from steel tube....I don't really want to get involved in the square versus round debate but im sure people are mainly just trying to build the best they can on a budget and get some fun out of it.I'm one of those people who always needs to eel that extra bit of advantage or push a bit of a barrier with technology and it seems the chassis of a locost would be different to have as a project.
I would be interested to see the level of documentation the inspectors would need to get a pass (i wouldnt have any problem providing figures etc)as I'm not sure what they would be looking for any links would be interesting.but again I would be interested not what the technical limitations are but if the actual process of getting it through qualification would kill the project or introduce compromise
iank - 28/5/11 at 06:34 AMThe problem with monocoques are that people are basically conservative (small c), and it's very hard to understand how a monocoque will hold up in an accident where people are more confident that 'more triangles' will get you through. Whether they are right or not isn't really the point, experimenting and refining designs isn't really feasible with composites and aluminium isn't as easy to modify as steel tube chassis.
The Robin Hood Lightweight debacle didn't help.
p.s. there was a pdf presentation kicking around the web showing a carbon-fibre spaceframe technique which Caterham were involved with. u2u your email if you want a copy
designer - 28/5/11 at 07:11 AMThere is one thing that always stands out in this debate.
A round tube chassis will always look better than a square tube one.
littlefeller - 28/5/11 at 09:25 PManyone modded a chassis to create a different car?
Peteff - 28/5/11 at 11:18 PMquote:
Originally posted by designer
There is one thing that always stands out in this debate.
A round tube chassis will always look better than a square tube one.
In your opinion? I think square looks better
Bare - 29/5/11 at 03:38 AMWhot a silly discussion.
Obviously every Twit who has built a marginally designed Locost /Haynes Chassis is gonna swear up and down on their Mother's Grave that square is the Holy Grail.
Total waste of time arguement.
Ever wonder why NO bicycles use square tubings ?? :-)
[Edited on 29/5/11 by Bare]
phelpsa - 29/5/11 at 09:25 AMquote:
Originally posted by Bare
Ever wonder why NO bicycles use square tubings ?? :-)
Because it looks crap?
compositepro - 29/5/11 at 09:26 AMbicycles do use square tubing
alistairolsen - 29/5/11 at 09:39 AMSo,
If we're discussing composite chassis....
Beyond the IVA difficulties which are basically legislative and should be easily enough satisfied if one has done the proper calculations to design a chassis rather than just boding in laminate till it looks right, and the inherent distrust some people seem to have of "plastic", to my mind the biggest difficulty for the home builder is the transition from carrying the load in plane in the laminate, and bolted hard points, for instance suspension mounts. There seem to be vairous ways around this, from machined hard points which are clamped in from both sides and bonded in place offer a large surface, to machined bulkheads, to tube frame suspension boxes mounted to either end of a body tub.....
For years, yachts ran loads into bulkheads and so on but in recent years many have gone for a steel or stainless steel internal subframe to take the keel and rigging loads, thus lightening the laminate in the hull, much like the tube frame suspension boxes would.
It's all a question of how to best achieve high structural efficiency..
indykid - 29/5/11 at 10:05 AMquote:
Originally posted by Bare
Whot a silly discussion.
Obviously every Twit who has built a marginally designed Locost /Haynes Chassis is gonna swear up and down on their Mother's Grave that square is the Holy Grail.
Total waste of time arguement.
Ever wonder why NO bicycles use square tubings ?? :-)
What a silly response to a 'silly' argument.
The engineering texts of history suggest that a square section is better for the majority of a spaceframe. For race cars, exotic tube specifications only come in round, so a lighter spaceframe can be made in that material.
Comparing mild steel profiles, the square gives a better distribution of material for the stresses involved.
Bikes? Round tube? It's what people who don't understand the theory expect and a pushbike frame is unfaired, so aesthetics play a larger part in the design. However, a seat post is easiest to make in round since it can be more easily clamped by anther round tube, as are the headstock tube and bottom bracket tube since they have to house bearings, so it's a matter of convenience too. You'll find a lot of bike manufacturers use elliptical section tube which is trying to achieve exactly what square tube provides. A more efficient distribution of material, just in a more aesthetically pleasing form.
Square may look agricultural, but just because you don't understand the theory, doesn't mean you can shout it down by finding whichever industrial application suits your cause.
littlefeller - 29/5/11 at 10:39 AMthats funny, i was thinking along the same lines, just have tube boxes at each end. can anyone think of a way to build a tube box without weld? either square or round.
compositepro - 29/5/11 at 11:05 AMquote:
Originally posted by alistairolsen
So,
If we're discussing composite chassis....
Beyond the IVA difficulties which are basically legislative and should be easily enough satisfied if one has done the proper calculations to design a chassis rather than just boding in laminate till it looks right, and the inherent distrust some people seem to have of "plastic", to my mind the biggest difficulty for the home builder is the transition from carrying the load in plane in the laminate, and bolted hard points, for instance suspension mounts. There seem to be vairous ways around this, from machined hard points which are clamped in from both sides and bonded in place offer a large surface, to machined bulkheads, to tube frame suspension boxes mounted to either end of a body tub.....
For years, yachts ran loads into bulkheads and so on but in recent years many have gone for a steel or stainless steel internal subframe to take the keel and rigging loads, thus lightening the laminate in the hull, much like the tube frame suspension boxes would.
It's all a question of how to best achieve high structural efficiency..
which yachts are these??
alistairolsen - 29/5/11 at 11:07 AMquote:
Originally posted by littlefeller
thats funny, i was thinking along the same lines, just have tube boxes at each end. can anyone think of a way to build a tube box without weld? either square or round.
Why would you want to? if you're working with tube, welding is still going to be the most convenient fabrication method?
alistairolsen - 29/5/11 at 11:10 AMquote:
Originally posted by compositepro
quote:
Originally posted by alistairolsen
So,
If we're discussing composite chassis....
Beyond the IVA difficulties which are basically legislative and should be easily enough satisfied if one has done the proper calculations to design a chassis rather than just boding in laminate till it looks right, and the inherent distrust some people seem to have of "plastic", to my mind the biggest difficulty for the home builder is the transition from carrying the load in plane in the laminate, and bolted hard points, for instance suspension mounts. There seem to be vairous ways around this, from machined hard points which are clamped in from both sides and bonded in place offer a large surface, to machined bulkheads, to tube frame suspension boxes mounted to either end of a body tub.....
For years, yachts ran loads into bulkheads and so on but in recent years many have gone for a steel or stainless steel internal subframe to take the keel and rigging loads, thus lightening the laminate in the hull, much like the tube frame suspension boxes would.
It's all a question of how to best achieve high structural efficiency..
which yachts are these??
danish X-yachts were one of the first but nowadays Salona, hanse (I believe) to name but a few.
compositepro - 29/5/11 at 11:19 AMquote:
Originally posted by alistairolsen
quote:
Originally posted by compositepro
quote:
Originally posted by alistairolsen
So,
If we're discussing composite chassis....
Beyond the IVA difficulties which are basically legislative and should be easily enough satisfied if one has done the proper calculations to design a chassis rather than just boding in laminate till it looks right, and the inherent distrust some people seem to have of "plastic", to my mind the biggest difficulty for the home builder is the transition from carrying the load in plane in the laminate, and bolted hard points, for instance suspension mounts. There seem to be vairous ways around this, from machined hard points which are clamped in from both sides and bonded in place offer a large surface, to machined bulkheads, to tube frame suspension boxes mounted to either end of a body tub.....
For years, yachts ran loads into bulkheads and so on but in recent years many have gone for a steel or stainless steel internal subframe to take the keel and rigging loads, thus lightening the laminate in the hull, much like the tube frame suspension boxes would.
It's all a question of how to best achieve high structural efficiency..
which yachts are these??
danish X-yachts were one of the first but nowadays Salona, hanse (I believe) to name but a few.
Are they racing yachts
alistairolsen - 29/5/11 at 11:21 AMnot as such, they're of the cruiser/racer genre, but tbh so is any boat build of grp in the last 20 years! A slightly upmarket equivalent of the French stuff used the world over as charter boats.
Volvorsport - 29/5/11 at 11:23 AMhow do GTMs et al , pass IVA with their complete GRP monocoque chassis ?
the australian built monocoque seven , uses ally honecomb for the tub .
reason for steel tube is its cheap , it cannot be beaten for that .
probably thats the biggest reason why i went the way with my chassis that i did .
the biggest problem with a composite chassis is the engine bay , there just isnt enough area to make the torsion boxes , itll be expensive to make damn sure that its strong enough with expensive pre preg carbon and an autoclave .
you coud do it with hand lay up , but , as above you cant be 100% sure .
( you could make an RH stainless monocoque by welding some inadequate stainless together and watch it fall apart around you , or even a pop riveted ally one with inadequate design) .
if you could do it cheaply , it probably wouldnt look like a seven , which is really the nub of the matter when it came to buiding my own , i should have done something else like a monocoque with mid engined t5 motor .
ahhh well we live and learn .
littlefeller - 29/5/11 at 12:37 PMquote:
Originally posted by alistairolsen
quote:
Originally posted by littlefeller
thats funny, i was thinking along the same lines, just have tube boxes at each end. can anyone think of a way to build a tube box without weld? either square or round.
Why would you want to? if you're working with tube, welding is still going to be the most convenient fabrication method?
because i tried welding ally tube but wasnt any goodguess i will just have to use steel square
alistairolsen - 29/5/11 at 12:47 PMto be honest, I wouldnt want to use alloy tube for a spaceframe construction. It's different if its a machined billet bulkhead, or a honeycombe monocoque.
JF - 29/5/11 at 01:08 PMAnd if you do want to use ally, design it properly. And invest in the proper equipment (TIG welder) and invest in the proper training to use said equipment.
Besides all that... ally isn't really the right material for a spaceframe. As discussed on here many times before....
scootz - 29/5/11 at 02:27 PMYay... couldn't wait for this one to turn to ali spaceframes!
Can we do MSA compliant roll-cages after we've done this one!?
littlefeller - 29/5/11 at 03:20 PMit still doesnt answer my question, is there another way other than welding. prehaps i should look at some construction internet sites
indykid - 29/5/11 at 03:50 PMquote:
Originally posted by littlefeller
it still doesnt answer my question, is there another way other than welding. prehaps i should look at some construction internet sites
Bolts, adhesive, lashing, chewing gum.......
JF - 29/5/11 at 03:55 PMDuct tape!
iank - 29/5/11 at 04:08 PMMy bike uses triangular alloy tubes.
[Edited on 29/5/11 by iank]
Neville Jones - 29/5/11 at 05:48 PMquote:
Originally posted by compositepro
quote:
Originally posted by alistairolsen
So,
If we're discussing composite chassis....
Beyond the IVA difficulties which are basically legislative and should be easily enough satisfied if one has done the proper calculations to design a chassis rather than just boding in laminate till it looks right, and the inherent distrust some people seem to have of "plastic", to my mind the biggest difficulty for the home builder is the transition from carrying the load in plane in the laminate, and bolted hard points, for instance suspension mounts. There seem to be vairous ways around this, from machined hard points which are clamped in from both sides and bonded in place offer a large surface, to machined bulkheads, to tube frame suspension boxes mounted to either end of a body tub.....
For years, yachts ran loads into bulkheads and so on but in recent years many have gone for a steel or stainless steel internal subframe to take the keel and rigging loads, thus lightening the laminate in the hull, much like the tube frame suspension boxes would.
It's all a question of how to best achieve high structural efficiency..
which yachts are these??
CompositesPro, I get the impression you may be younger than the first yachts which used a metal internal girder setup. The first (in modern times)was a 39' raceboat designed by Ron Holland, named Imp, built in 1979 for the Admiral's Cup. There was a succession of raceboats up to the mid 80's and up to 80+ ft using the same method of internal structure to carry the loads, and then the hull just gave it form and kept the water out. Two of the most well known Maxis were Kialoa, and the UK owned Condor. ( I helped crew Imp on its delivery to Florida after the AC.) Wooden yachts and ships in the 1800's used metallic structures to carry major loads.
Todays race boats try to emulate a girder structure using carbon girders/girder shapes built in to the deck and hull. And sometimes they get it wrong, with catastrophic results. I've been designing in composites for near 40 years, and see people still ignore, or are blissfully ignorant, of some of the most basic engineering precepts of tension and compression loads. All (well, nearly) failures I've seen have been in compression.
As for the kits that use a grp monocoque, the SVA>IVA makes it clear how things like suspension and particularly seatbelt mounting points are integrated. In essence, you need to use large (read thick and heavy) steel plates bonded in, and the mounts then bolt through these.
I've put a honeycomb chassis through SVA many years ago, and needed all of the hundred pages or so of calcs and pics before it was finally passed.
Cheers,
Nev (the sailor!!
[Edited on 29/5/11 by Neville Jones]
compositepro - 29/5/11 at 06:52 PMquote:
Originally posted by Neville Jones
quote:
Originally posted by compositepro
quote:
Originally posted by alistairolsen
So,
If we're discussing composite chassis....
Beyond the IVA difficulties which are basically legislative and should be easily enough satisfied if one has done the proper calculations to design a chassis rather than just boding in laminate till it looks right, and the inherent distrust some people seem to have of "plastic", to my mind the biggest difficulty for the home builder is the transition from carrying the load in plane in the laminate, and bolted hard points, for instance suspension mounts. There seem to be vairous ways around this, from machined hard points which are clamped in from both sides and bonded in place offer a large surface, to machined bulkheads, to tube frame suspension boxes mounted to either end of a body tub.....
For years, yachts ran loads into bulkheads and so on but in recent years many have gone for a steel or stainless steel internal subframe to take the keel and rigging loads, thus lightening the laminate in the hull, much like the tube frame suspension boxes would.
It's all a question of how to best achieve high structural efficiency..
which yachts are these??
40 years experience...that must be one long list of companies
CompositesPro, I get the impression you may be younger than the first yachts which used a metal internal girder setup. The first (in modern times)was a 39' raceboat designed by Ron Holland, named Imp, built in 1979 for the Admiral's Cup. There was a succession of raceboats up to the mid 80's and up to 80+ ft using the same method of internal structure to carry the loads, and then the hull just gave it form and kept the water out. Two of the most well known Maxis were Kialoa, and the UK owned Condor. ( I helped crew Imp on its delivery to Florida after the AC.) Wooden yachts and ships in the 1800's used metallic structures to carry major loads.
Todays race boats try to emulate a girder structure using carbon girders/girder shapes built in to the deck and hull. And sometimes they get it wrong, with catastrophic results. I've been designing in composites for near 40 years, and see people still ignore, or are blissfully ignorant, of some of the most basic engineering precepts of tension and compression loads. All (well, nearly) failures I've seen have been in compression.
As for the kits that use a grp monocoque, the SVA>IVA makes it clear how things like suspension and particularly seatbelt mounting points are integrated. In essence, you need to use large (read thick and heavy) steel plates bonded in, and the mounts then bolt through these.
I've put a honeycomb chassis through SVA many years ago, and needed all of the hundred pages or so of calcs and pics before it was finally passed.
Cheers,
Nev (the sailor!!
[Edited on 29/5/11 by Neville Jones]
Volvorsport - 29/5/11 at 07:43 PMquote:
Originally posted by indykid
quote:
Originally posted by littlefeller
it still doesnt answer my question, is there another way other than welding. prehaps i should look at some construction internet sites
Bolts, adhesive, lashing, chewing gum.......
self piercing rivets ..............
littlefeller - 29/5/11 at 07:44 PMas we are talking alternative chassis, anyone else done anything different
iank - 29/5/11 at 07:57 PMquote:
Originally posted by littlefeller
as we are talking alternative chassis, anyone else done anything different
Don't think so on here - at least none that have been finished that I can think of, but Autospeed has some articles on more adventurous techniques if you hunt around.
e.g. An "origami" monocoque construction using grp honeycomb.
http://autospeed.com/cms/A_110989/article.html
Confused but excited. - 29/5/11 at 07:58 PMquote:
Originally posted by v8kid
quote:
Originally posted by Confused but excited.
All this is very interesting to a numpty like me (note my LCB name), but as DDD stated "On non structural parts you could use smaller tube like 3/4" 18swg."
This got me more confused. My question is; What parts of a locost/space frame type chassis are non-structural?
Or have I missed something?
This is not meant to be snide, so apologies to anyone who may think different. Just trying to expand my meagre knowledge.
The bits you hang other stuff off! Like seats, gearlever, steeringwheel, radiator, engine/box - that sort of stuff
BTW square v round it depends on how you are loading it, bending (loads of different planes), torsion, buckling, shear - cant think of any other modes offhand - the point is you have to know how the particular member is loaded before making a decision.
Great thread.
Cheers!
No mate, they are called brackets but thanks for taking the time to answer my question.
[Edited on 29/5/11 by Confused but excited.]
Theshed - 29/5/11 at 08:15 PMYes......
compositepro - 29/5/11 at 08:56 PMquote:
Originally posted by iank
quote:
Originally posted by littlefeller
as we are talking alternative chassis, anyone else done anything different
Don't think so on here - at least none that have been finished that I can think of, but Autospeed has some articles on more adventurous techniques if you hunt around.
e.g. An "origami" monocoque construction using grp honeycomb.
http://autospeed.com/cms/A_110989/article.html
i love it when someone takes a different angle on things
littlefeller - 29/5/11 at 09:37 PMi never do things the exepted way
[Edited on 29/5/11 by littlefeller]
alistairolsen - 30/5/11 at 06:43 AMI've seen that article before and always thought it would be a nice way to do a hillclimber. The same issues with load spreading prevail though!
Volvorsport - 30/5/11 at 09:31 AMits pretty much the same stuff as teklam www.teklam.com
teklam is available in 25mm thickness , so could be bonded in between the basic square section frame , a hybrid monocoque .
Neville Jones - 30/5/11 at 10:15 AMquote:
40 years experience...that must be one long list of companies
No, a long list of build projects. Like civil construction, you finish one project and move on to another. And then you get an offer to work for a consulting co. and life becomes civilised.
Cheers,
Nev.
compositepro - 30/5/11 at 02:18 PMcivil construction? I was under the impression you had consulted for motorsports or yacht builders?
Neville Jones - 30/5/11 at 03:04 PMquote:
Originally posted by Neville Jones
quote:
40 years experience...that must be one long list of companies
No, a long list of build projects. Like civil construction, you finish one project and move on to another. And then you get an offer to work for a consulting co. and life becomes civilised.
Cheers,
Nev.
Can you not comprehend plain english??? LIKE-Similar to but not the same.
LIKE CIVIL CONSTRUCTION!!!!! I have a son who is a civil engineer. They tend to build a bridge or railway or highway, then the job is finished and they have to get another job!! Then when the wanderlust disappears, they get a steady job with a consulting co.
What do you think I do, make carbon fibre bridges and fibreglass roads?? Mind you, there is a lot more composite design and fibres in concrete these days than most would be aware of.
Cheers,
Nev.
[Edited on 30/5/11 by Neville Jones]
compositepro - 30/5/11 at 03:11 PMI have trouble with forums there lots of stuff that gets written that can be taken out of context
littlefeller - 30/5/11 at 05:17 PMhave you got a composite design in mind? what you thinking?
compositepro - 2/6/11 at 06:20 PMi have a lot of ideas for this ,however i mentioned previously that usually the hobby car builders are usually quite inventive and there doesn't seem to be so many chassis using composites this leads me to a few conclusions but i'm pretty sure a monocoque wouldn't be beyond the realms of very possible even at this level of car building.
I was keen to see the responses but like i alluded to earlier from looking at whats around the kit car forums and there seems to be two direct ways of looking at it
without going into the square is better than round debate and thats that steel is simple and relatively easy to work with
but im pretty sure with the right techniques you could improve on whats about at the moment (improvement being one of those very subjective words)
Theres definitely a lack of understanding in materials other than steel and i suppose that brings steel even closer to the fore when it comes to building these things and reinforces the other materials get discarded approach to building these cars...just because you can doesnt mean you have to but sometimes its just nice to experiment with something else
littlefeller - 2/6/11 at 07:34 PM[Edited on 2/6/11 by littlefeller] not sure where the last post went? i would be intrested to have ago, but i dont know how. been playing around with different chassis designs trying to settle on one direction. now gone back to steel tube but exploring different construction techniques
[Edited on 2/6/11 by littlefeller]
littlefeller - 5/6/11 at 07:43 AMquote:
Originally posted by compositepro
I have trouble with forums there lots of stuff that gets written that can be taken out of context
By littlefeller2010 at 2011-06-05
[Edited on 5/6/11 by littlefeller]
iank - 5/6/11 at 07:52 AMFWIW the original is here http://xkcd.com/386/ along with lots of other good ones.
littlefeller - 5/6/11 at 08:06 AMwere nearly on page 5 and still no answer, there must be a maths genius on here somewhere who can end this.
anyone else got a cool idea for a chassis
Mike Wood - 5/6/11 at 12:24 PMHi
Some early Marcos cars had wooden chassis bonded into grp bodies - the first Marcos ('gullwing'?) and the series pruduction Marcos GT with a range of engines. Jem Marsh's book on Marcos has some interesting design detail sketches by the designer Frank Costin on attaching suspension and other items to the wooden chassis box members. See: http://home.swipnet.se/~w-90803/wooden.htm Marcos did switch to using steel tube chassis - probably due to cost in labour and materials of wooden chassis.
Worth noting that wooden chassis often include lots of fabricated metal attachment brackets and components, including steel tube subframes for suspension mounting. Time and skill needed to fabricate these.
Clan Crusaders had grp monocoque shells which included marine plywood sections, mainly in forming part of the structural side cills and the rear bulkhead.
A lot of inspiration for wooden car structures can come from aircraft practice. Some small wooden aircraft have wooden fuselage structures akin to steel tube spaceframes (which many light aircraft use, such as the Pitts Special, as do racing cars, as well as stressed skin aluminium monocoques - 'spam cans' such as Cessna 172 and commercial ailrliners e.g. Boeing 737) sides skinned with plywood and the whole structure covered in fabric that is tautened to become part of the structure with the use of a fabric cellulose-based paint ('aircraft dope') Google 'Evans VP1', 'Taylor Monoplane', 'Issacs Spitfire', 'Issacs Fury', 'Williams Flitzer' and 'Volmer Sportsman'. And there are the wooden monocoque aircraft fuselages, such as the Dehavilland Mosquito which was a wooden composite with a balsa wood core skinned either side with plywood. Better not mention the huge and overweight Douglas Spruce Goose!
It should be possible to produce a rear engined open cockpit single or two seater racing car with a wooden central tub - using a mixture of aircraft grade spruce or Douglas fir frame covered in marine plywood to make up box sections/pontoons as well as using larger thickness plywood for bulheads (and gluing on aluminium sheet to make a fireproof engine structural bulkhead). But it would be easier and cheaper to make a steel tube chassis, so you'd only pick wood to be different, if you had the skills/materials, and you could still do some metalwork.
Not sure if there are many people left that have the experience of designing with such materials (spruce and plywood), including making sure that the structure isn't too heavy.
Even in the homebuilt aircraft area, many people are using 'plastic' composites, as well as steel tube, google 'EAA' (Experimental Aircraft Association in USA) and the Light Aircraft Association (UK, formerly the Popular Flying Association) for info.
One last thought on wooden structures - apart from lack of wide knowledge and acceptance, the cost of materials is high, as well as time to build - you'd only want to be using marine plywood (known quality, strength as well as good weather resistance) and aircraft grade spruce or Douglas fir that you could strength grade. There are special high strength glues developed for wooden aircraft that would be ideal, but the temptation these days would be to use epoxy resin. Wood is a great material to laminate grp to, unlike steel or aluminium, so the grp can be used structurally.
One of my great car disappointments was a Scimitar SST that was so heavy - nice galvanised chassis, but heavy grp body - could have had better design of each element and integration of them. It was heavier than the Scimitar SS1 that it was developed from (just like all modern updates of car models!)
Cheers
Mike
[Edited on 5/6/11 by Mike Wood]
[Edited on 5/6/11 by Mike Wood]
[Edited on 5/6/11 by Mike Wood]
[Edited on 5/6/11 by Mike Wood]
[Edited on 5/6/11 by Mike Wood]
littlefeller - 5/6/11 at 02:02 PMwhat a cool idea. much more intresting than square v round but this thread got hijacked ages ago, and still no silly posts sugesting paper mache
compositepro - 5/6/11 at 03:45 PMA different idea altogether mike.....I was wondering about wood....mother natures very own composite material....
I just read something on titanium exhausts which was a remarkably strange article..but overall if you have money to burn and all the gear But no idea an essential item
A ti locust frame nearly half the weight but ooo oh no half the stiffness....unless you get clever with wall and tube dziameters
the creativity of the EAA....something amazes me every time I see what those guys get up to
indykid - 5/6/11 at 04:08 PMquote:
Originally posted by compositepro
A ti locust frame nearly half the weight but ooo oh no half the stiffness....unless you get clever with wall and tube diameters
I'd love to see it done as a technical exercise, but I'd hate to see the bill for the argon!
Volvorsport - 5/6/11 at 06:02 PMwood doesnt fatigue either , if it doesnt rot .......
the composite chassis /monocoque suits a mid engined design much better than a seven design .
the trick to to bonding grp or composite onto tube frames is to coat it with polyurethane varnish beforehand .
its how i bonded my kevlar in .
oh , and yes , you could use pultruded tubes but , youl have to do lots of digging on finding the best joining method , and possibly GRP isnt the best material in a tube , carbon would be , since you want stiffness not flexibililty .
[Edited on 5/6/11 by Volvorsport]
littlefeller - 5/6/11 at 07:38 PManyone got any info on wooden chassis?
Volvorsport - 5/6/11 at 08:36 PMhttp://home.swipnet.se/~w-90803/
