Longerr
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| posted on 23/5/11 at 11:02 AM |
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Tube Frame
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
http://locost.webnode.cz/fotogaleria our build so far
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mark chandler
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| posted on 23/5/11 at 11:07 AM |
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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
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jossey
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| posted on 23/5/11 at 11:19 AM |
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try here.
http://www.locostbuilders.co.uk/viewthread.php?tid=17998
Thanks
David Johnson
Building my tiger avon slowly but surely.
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blakep82
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| posted on 23/5/11 at 11:36 AM |
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like this?
http://www.locostbuilders.co.uk/forum/7/viewthread.php?tid=154561
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Doctor Derek Doctors
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| posted on 23/5/11 at 11:59 AM |
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quote:
Originally posted by blakep82
like this?
http://www.locostbuilders.co.uk/forum/7/viewthread.php?tid=154561
Yay! I'm now the proud owner of a car that has become a reference point.
Steve Hignett built the Chassis, the thread detailing the build of the frame is here:
http://www.locostbuilders.co.uk/viewthread.php?tid=132958
You're welcome to come and have a look at the car if you are anywhere near the Gloucestersgire area.
Personally i think its a much better way to build a car, with a much better result. Although the added strength, chassis stiffness compared to the
required weight may be overkill for anything other than a Race or serious track car.
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Longerr
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 posted on 23/5/11 at 12:42 PM |
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Thank you very much  , I will be now studying those threads and topics
http://locost.webnode.cz/fotogaleria our build so far
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MikeRJ
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| posted on 23/5/11 at 03:57 PM |
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quote:
Originally posted by Doctor Derek Doctors
[Personally i think its a much better way to build a car, with a much better result.
It's a much more difficult way to build a car with a neater looking result and a possible small weight or stiffness advantage.
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Neville Jones
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| posted on 23/5/11 at 05:25 PM |
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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]
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Doctor Derek Doctors
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| posted on 23/5/11 at 06:25 PM |
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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?
Odd one that, we could assume that for a given weight round tube is far superior?
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.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Neville Jones
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| posted on 24/5/11 at 09:54 AM |
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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.
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Doctor Derek Doctors
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| posted on 24/5/11 at 12:23 PM |
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quote:
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.
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Longerr
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| posted on 24/5/11 at 02:41 PM |
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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
http://locost.webnode.cz/fotogaleria our build so far
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Doctor Derek Doctors
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| posted on 24/5/11 at 03:38 PM |
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quote:
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.
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Neville Jones
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| posted on 24/5/11 at 04:31 PM |
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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. )There's far too much BS from youngsters (and pretenders) on here, who've 'read
it in a book', or worse still, on that dreaded Wikipedia!!!
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.
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littlefeller
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| posted on 24/5/11 at 04:32 PM |
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interesting 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
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phelpsa
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| posted on 24/5/11 at 04:58 PM |
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http://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.
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Doctor Derek Doctors
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| posted on 24/5/11 at 09:20 PM |
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quote:
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. )There's far too much BS from youngsters (and pretenders) on here, who've 'read
it in a book', or worse still, on that dreaded Wikipedia!!!
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]
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flibble
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| posted on 24/5/11 at 09:29 PM |
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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?
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Neville Jones
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| posted on 25/5/11 at 10:50 AM |
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[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.
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phelpsa
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| posted on 25/5/11 at 11:30 AM |
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quote:
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?
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Neville Jones
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| posted on 25/5/11 at 11:33 AM |
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Bickering?
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.
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phelpsa
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| posted on 25/5/11 at 11:42 AM |
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quote:
Originally posted by Neville Jones
Should you not be studying for exams?
Cheers,
Nev.
Point taken.
Over and out.
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blakep82
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| posted on 25/5/11 at 11:44 AM |
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remind 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 
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Liam
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| posted on 25/5/11 at 01:12 PM |
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I 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.
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littlefeller
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| posted on 25/5/11 at 04:14 PM |
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quote:
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?
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