cymtriks
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| posted on 8/8/04 at 12:02 PM |
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chassis analysis, Mine and Wesleys
I have recently finished a rewrite of my chassis analysis document. This is posted on the Yahoo forum and on the Oz (Ogden) locost7.info site.
I have read Wesleys analysis on the Ogden site. The following differences aren't an attempt to disagree with Wesley, I'm just explaining
the differences.
1) Wesley includes an X brace between the FU tubes. I don't as I thought that this might give clearance problems with some engines.
2) Wesley assumes that riveted alloy panels are structural. I don't as I've heard that riveted monocoques can lose a third of their
stiffnes in their first year. I've also heard of riveted floors falling out.
3) Wesleys "ring brace" is similar in concept to my "double Y braced chassis". The diference is that I've chosen an
arrangement which minimises the problems of small angles between tubes. It can be very tricky to properly cut and weld shallow angle joints.
4) I don't panel the full footwells as I think this might give foot room problems with the book 13 inch high chassis. 13 inches sounds a bit
tight to me.
5) my analysis is aimed at helping a home builder, not at getting an MSC. I've tried to cut down on theory and to keep the modifications
simple.
6) I've included ladder frames as I think these are under rated.
7) Wesley gets higher stiffness but this is largely due to our assumptions regarding alloy panels. I have sacrificed stiffness for simplicity and ease
of build in some cases and I've tried to keep the chassis as close to the book design as possible. He uses the same software that I have used by
the way.
Well done Wesley and thankyou for him and Luego for letting us see his work.
Perhaps we could do with a files section on this forum?
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Dale
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| posted on 8/8/04 at 04:19 PM |
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Both documents have been interesting reads and helpfull. I agree that a files section would be good but I think a Documents section and a sepereate
files/executables section would be good.
Documents for writeups, fixed spreadsheets such as balljoint specs drawings such as mcsorlys -- if acceptable to the originators. A files section
for programs such as spreadsheets for suspension, programs like the gearcalc for gear ratios ect.
Just my 2 cents worth
Dale
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stressy
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| posted on 8/8/04 at 04:25 PM |
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Its very easy to enhance the stiffness of your chassis through numerical methods and not be able to achieve it in reality as cymtriks suggests.
I viewed the rivited panels as skins to keep the wind out and nothing more. Any benefit they give is a bonus.
In order for them to work you would need to either bond them (properly not just slap in some glue!!), or use a good pitch of solid rivits, and use a
good grade of material. AS already mentioned the rivits have a tendancy to work loose overtime and become less efficient, as such bonding is my
favorite.Then you may get close to achieving a decent stiffening effect proportional to the frame they are fixed to.
Its also worth considering whether to fix the diagonals to the skins or not, as no doubt cymtriks has considered, shear in triangular panels is rather
interesting!!
On the ring frame topic, wesleys is neat but tricky and cymtriks is neat and a little simpler, very similar to the design used by caterham. If you
building at home either one will be a good choice.
Both analyse made a good read guys,
cheers
Chris
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pbura
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| posted on 8/8/04 at 05:13 PM |
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I'm very happy with all the work that's been done by both parties, giving a nice assortment of mods to be selected based on the
builder's preferences and car layout.
Cymtriks, a couple of enhancements in v2.0 that I especially appreciated were the section about springing and anti-roll bars, and the one about
increasing tube sections for more powerful engines, IRS, etc.
Thanks! 
Pete
Pete
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stressy
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| posted on 9/8/04 at 06:56 AM |
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info for cymtriks
Hi mate, i had a look at your version 2 last night and spotted something you may be interested in. On p.20 you have a rear corner weight of 375lb
(170kg) of which 65lb (30kg) is unsprung.
From measurements i collected i would suggest this is a little low. I measured a live axle assy as 56kg unsprung and 7 kg sprung taking a sort of semi
sprung as 50:50 sprung/unsprung.
In additon there would be a further 30 to 40kg for wheels so......assuming 35kg for wheels/tyres, ..corner unsprung would be around 45kg (100lbs)
I hope this may be of some use,
cheers
chris
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cymtriks
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| posted on 10/8/04 at 08:29 PM |
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The weight is to illustrate how the equations work and I do advise checking that the assumed weights are appropriate before using them in the text.
I'm concerned that I was so far out though. I can't recall where my weight came from. I thought it was from staniforth but his book says
that with a live axle, rally tyres and steel wheels the USW can be as high as 100 to 150 lbs. This ties in fairly well with your numbers.
Thanks for the feedback. I'll bare the weight in mind when an update is due.
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