phelpsa
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| posted on 29/5/11 at 09:25 AM |
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quote:
Originally posted by Bare
Ever wonder why NO bicycles use square tubings ?? :-)
Because it looks crap? 
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compositepro
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| posted on 29/5/11 at 09:26 AM |
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bicycles do use square tubing
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alistairolsen
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| posted on 29/5/11 at 09:39 AM |
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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..
My Build Thread
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indykid
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| posted on 29/5/11 at 10:05 AM |
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quote:
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.
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littlefeller
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| posted on 29/5/11 at 10:39 AM |
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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.
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compositepro
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| posted on 29/5/11 at 11:05 AM |
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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??
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alistairolsen
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| posted on 29/5/11 at 11:07 AM |
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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?
My Build Thread
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alistairolsen
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| posted on 29/5/11 at 11:10 AM |
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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.
My Build Thread
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compositepro
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| posted on 29/5/11 at 11:19 AM |
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quote:
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
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alistairolsen
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| posted on 29/5/11 at 11:21 AM |
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not 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.
My Build Thread
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Volvorsport
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| posted on 29/5/11 at 11:23 AM |
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how 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 .
www.dbsmotorsport.co.uk
getting dirty under a bus
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littlefeller
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| posted on 29/5/11 at 12:37 PM |
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quote:
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 good guess i will just have to use steel square
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alistairolsen
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| posted on 29/5/11 at 12:47 PM |
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to 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.
My Build Thread
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JF
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| posted on 29/5/11 at 01:08 PM |
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And 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....
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scootz
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| posted on 29/5/11 at 02:27 PM |
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Yay... couldn't wait for this one to turn to ali spaceframes! 
Can we do MSA compliant roll-cages after we've done this one!? 
It's Evolution Baby!
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littlefeller
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| posted on 29/5/11 at 03:20 PM |
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it still doesnt answer my question, is there another way other than welding. prehaps i should look at some construction internet sites
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indykid
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| posted on 29/5/11 at 03:50 PM |
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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.......
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JF
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| posted on 29/5/11 at 03:55 PM |
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Duct tape!
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iank
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| posted on 29/5/11 at 04:08 PM |
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My bike uses triangular alloy tubes.
[Edited on 29/5/11 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Neville Jones
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| posted on 29/5/11 at 05:48 PM |
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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??
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]
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compositepro
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| posted on 29/5/11 at 06:52 PM |
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quote:
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]
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Volvorsport
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| posted on 29/5/11 at 07:43 PM |
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quote:
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 ..............
www.dbsmotorsport.co.uk
getting dirty under a bus
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littlefeller
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| posted on 29/5/11 at 07:44 PM |
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as we are talking alternative chassis, anyone else done anything different
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iank
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| posted on 29/5/11 at 07:57 PM |
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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
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Confused but excited.
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| posted on 29/5/11 at 07:58 PM |
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quote:
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.]
Tell them about the bent treacle edges!
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