Big Will
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| posted on 10/1/04 at 05:21 PM |
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Ally Chassis
Hey Y'all. I am planning on a Rover V8 powered Locost using McSorleys 7+442 plans but adapting to sierra irs. My aim is to use duralium or
another aluminium alloy to create a chassis. All joints will be braced or gusseted and the side and floor panels will be welded instead of riveted.
What other issues should I be aware of? I can't find anyone who has built an ally chassis. Why so few or am I missing something?
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Alan B
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| posted on 10/1/04 at 05:37 PM |
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There are so few because it's not considered a good idea......
My opinion:
Ali can be used for great car frame structures...just not spaceframes...if you are hell bent on Ali then a monocoque tub is your best bet...trouble is
it means a complete re-design and the experience and knowledge to pul it off....
Bottom line..it's your car...do what you like...but you would be well advised to stick with a regular mild steel tube space frame..IMO
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JoelP
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| posted on 10/1/04 at 05:39 PM |
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hi will. It has been done, though rarely due to two reasons (IIRC - im no expert!)
one, it is harder to weld than mild steel.
two, some say that ally chassis are more sensitive to vibration and fall apart if they are not well designed/welded/gusseted.
plus, the chassis isnt that heavy i think, so there may only be about 50kgs to save? thats a guess though. and maybe 50kgs is worth saving.
i would only do that though if i was using a good bike engine, to maximise the weight gain, though i recall that the rover v8 are quite light
anyway.
all the best anyway!
Joel
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Alan B
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| posted on 10/1/04 at 05:48 PM |
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Just to elaborate on Joel's second point I'll just paste from MK's FAQs..
"2. Can I get an aluminium chassis?
No. Aluminium chassis suffer from metal fatigue which leads to premature failure. The ones that were made were for demonstration puposes only
"
Basically, ali, unlike steel, has no safe level of stress below which it is imune from the effects of extended cyclic loading...i.e. fatigue...so as
Joel says it is subject to quite literally fallling apart, and not at high loadings either....
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chris.russell
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| posted on 10/1/04 at 05:51 PM |
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welcome to the locost forum 'big will'. if you have not done so try doing a search on ali chassis (top left of the page), there was some
discussion done at the beginning of 2003 on ali chassis - pros and cons. The general consensious was it would be great to have but its durability and
life span might pose some problems
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Big Will
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| posted on 10/1/04 at 06:32 PM |
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Ally Chassis
Woah! That was quick! Thanks you guys. Guess thats a "No" then. Just wanted to test the idea. Steel it is then. Thanks for your advice.
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type 907
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| posted on 10/1/04 at 07:03 PM |
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SLOW DOWN BIG WILL
You mentioned duralumin (aluminium/copper)
If you have the equipment and the expertise, understand the age hardening process, (and can afford it) go for it.
If it holds together a Jumbo, it'll hold a Big Will.
Paul G
Too much is just enough
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David Jenkins
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| posted on 10/1/04 at 08:22 PM |
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Paul,
I doubt whether a Locost will get the same maintenance routine as a Jumbo - complete strip-down & re-skin after 'x' hours, with all
parts periodically crack-tested between.
DJ
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type 907
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| posted on 10/1/04 at 11:51 PM |
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Hi David,
I do wholeheartedly accept your point.
I did however say, "IF" you have the "equipment", "expertise" &
"understanding" of this alloy, "go for it".
I do feel we tend to knock a newcomer to this forum for his ideas, when Big Will could be a gentleman with say, thirty years experience as an airframe
fitter.
As for my last comment, sorry, just saw a link between your name Big Will, and Jumbo.
ATB
Paul G
Too much is just enough
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Big Will
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| posted on 11/1/04 at 09:46 AM |
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ally chassis
Hello again. Can't say I have 30 yrs experience...yet. Got a mech eng degree and a few years building odds and sods and building up my
offroader, (plenty of opportunities for testing things to destruction!), and i've also built a hovercraft out of ally before, although i fully
appreciate stress fracturing in a car chassis as the loads are totally different. I did a study on the fracture patterns in aircraft landing wheels
and figured that if I could reinforce the most stressed areas of the chassis it might work although if I made it too rigid then the stresses would
simply go elsewhere. Still, thanks for all your support and advice. P.S. Does anyone have plans for a chassis where a sierra IRS simply bolts in as
opposed to a DeDion or double wishbone? I've read all the hoohaa about the pros and cons but I'm driving a 1.8 GLX at the mo and want to
use it as a donor. Just a thought. Thanks for all your help once again. Cheers, Will.
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Alan B
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| posted on 11/1/04 at 01:39 PM |
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quote:
Originally posted by type 907........I do feel we tend to knock a newcomer to this forum for his ideas........
907, I disagree with that point...I think it was a case of advice sought and advice given.....I'd be last the person to discourage anything
different...just like to point out any pitfalls that may be ahead.....
It's like any idea, if the issues are known and addressed, then almost anything is possible...
I'm not trying to be arguementative, but I'd hate to be labelled as negative or non-supportive...
Cheers,...
Alan
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blueshift
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| posted on 11/1/04 at 02:25 PM |
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quote:
Originally posted by Big Will
Does anyone have plans for a chassis where a sierra IRS simply bolts in as opposed to a DeDion or double wishbone? I've read all the hoohaa
about the pros and cons but I'm driving a 1.8 GLX at the mo and want to use it as a donor.
Are you aware of the GTS de-dion kit? that makes use of sierra running gear (diff, driveshafts, hubs, brakes) so a sierra is your donor, but you
don't have the weight of the whole sierra back end. We're planning to go GTS de-dion.
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Big Will
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| posted on 11/1/04 at 06:11 PM |
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Hey Blueshift. Looking at your spec it looks like we are after the same thing. 7+4, RV8, sierra based, etc. I've looked at a lot of sites now
and I am hovering between sierra subframe and DeDion. The subframe just seems so much simpler, no messing around with welding or calibrating all the
angles, etc. Just bolt onto the chassis and there you go. The weight saved using DeDion can't be that much and with a RV8 at the front, a
slightly heavier rear might balance her better and DeDion just seems a whole lot more complex than just using a ready made and set-up, bolt in unit. I
am open to all advice though. You lot have been very helpful so far. Much more so than I was expecting. What is your opinion of the GTS(?) DeDion
set-up? It's about £135, right? What Mods to the basic chassis are needed for it to fit? Thanks for any help.
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kingr
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| posted on 11/1/04 at 07:34 PM |
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Big Will,
While it's possible to use the whole Sierra sub assy, it's not often done for several reasons - firstly, it looks ugly because you can see
the outer mounts hanging down under the chassis, secondly, it's rather heavy - lot's of it's made from what looks like pressed 3mm
steel, thirdly, there's absolutely no adjustment available, and finally, semi trailing arms aren't the most high performance of suspension
designs.
If you don't want the hastle of building IRS, the GTS de dion kit seems a pretty good alternative.
Kingr
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David Jenkins
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| posted on 11/1/04 at 09:48 PM |
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Will,
As a newcomer you are probably not aware of the 'full and frank' discussions that arise when somebody proposes to use some material other
than mild steel!
Every so often someone proposes aluminium, stainless steel, some exotic steel, and so on. Most established builders try to discourage it as the
problems often outweigh the advantages.
However, people come along who confound these doubts, such as Paul (a.k.a. Type 907). He's building his chassis in stainless, having very many
years experience in welding that stuff professionally (and very nice it is too!).
I don't know your background - you might be an ace ali welder - but several professionals have shied away from everything except race track
chassis.
If you can do it, then go for it, but you may be safer on the road in a plain old mild steel chassis.
Best regards,
David
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chrisg
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| posted on 11/1/04 at 10:15 PM |
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I don't really think your welding skills really come into it.
Some Hillclimbers use ali chassis, but they are "lifed", replaced after sometimes as little as three outings. I don't think that
they are all poor welders, the difficulties of durability are just to difficult to overcome.
An aluminium monocoque might be the answer
Cheers
Chris
Note to all: I really don't know when to leave well alone. I tried to get clever with the mods, then when they gave me a lifeline to see the
error of my ways, I tried to incite more trouble via u2u. So now I'm banned, never to return again. They should have done it years ago!
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blueshift
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| posted on 12/1/04 at 04:36 PM |
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quote:
Originally posted by Big Will
Hey Blueshift. Looking at your spec it looks like we are after the same thing. 7+4, RV8, sierra based, etc. I've looked at a lot of sites now
and I am hovering between sierra subframe and DeDion. The subframe just seems so much simpler, no messing around with welding or calibrating all the
angles, etc. Just bolt onto the chassis and there you go.
...
What is your opinion of the GTS(?) DeDion set-up? It's about £135, right? What Mods to the basic chassis are needed for it to fit? Thanks for
any help.
I haven't seriously looked into the practicalities of attaching the sierra subframe to the locost chassis, are the mount points really so
conventiently located that it just bolts on?
As for welding and messing about with angles - if you're going to build a chassis you can't be that scared of welding, and from what I
understand of the GTS kit (I haven't seen one in the flesh yet.. should be soon) it will come all welded up with set toe and camber angles, you
just bolt it up to book-style trailing arm and panhard rod links.
I'm not entirely sure about the mods to the back, all I know is inferred from the PDF's on the GTS website. it seems that the back of the
tranny tunnel is widened and has flanges welded to it to bolt the diff onto, and the upward-angled tubes that run backwards under the axle in the book
chassis are changed to run horizontally at car-floor level with a little vertical connecty bit at the back. I think this is extra clearance for the
de-dion tube.
AFAIK yes the GTS kit is £135. I am planning to go and chat to Darren and see one in the flesh, take photos and measurements etc. Need to talk to him
about the mods needed to the kit so that it will bolt up to a +4 chassis, have discussed that with him briefly in email, he thought it wouldn't
be a problem, just a matter of moving the "ears" out.
hth
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JoelP
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| posted on 12/1/04 at 04:53 PM |
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And this from someone who is doing the subframe approach (me): dont bother.
the only reason im doing it is cos when i started i was a bit aprehensive of making an IRS system myself, and i wanted to use sierra running gear. The
subframe is heavy enough that it gets moved around on its wheels usually, and i once managed to drag it 4 meters sideways. Weighs shitloads and the
only good thing is that the semi-trailing arms all line themselves up.
If i knew about dedion when i started then i would've done it.
Live and learn? i will if the car doesnt kill me first...
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JoelP
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| posted on 12/1/04 at 04:55 PM |
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quote:
Originally posted by Big Will
The weight saved using DeDion can't be that much and with a RV8 at the front, a slightly heavier rear might balance her better
bear in mind that the engine is further back then a normal car and weight distribution is quite favourable normally. I certainly wouldnt ballast the
back!
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mangogroove
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| posted on 12/1/04 at 05:22 PM |
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The de-dion is the same as a live axle except the insides are open instead of inside a tube. Recon the weight is the same. If cateringvan used it for
long enough its ok by me as proven technology. 
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GO
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| posted on 12/1/04 at 05:31 PM |
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Overall weight probably roughly the same, but unsprung verses sprung weight will be different - de-dion, diff mounted on chassis so more sprung weight
and therefore less unsprung weight, which is a good thing.
EDIT - sorry, not meaning to be particularly pedantic, but thats my middle name around here, along with grumpy, letch, along with a few others 
[Edited on 12/1/2004 by GO]
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Big Will
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| posted on 13/1/04 at 09:34 PM |
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Hi everyone. Just wanted to say thank you all so much for all the support and advice you have given me so quickly and readily. It has certainly
cleared a lot of issues up. Gonna go for a sierra based DeDion with a +4 chassis and keep the RV8. Thought about a bike engine for a couple of hours
but just luuurve everything about the V8. Thanks, Will.
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stephen_gusterson
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| posted on 13/1/04 at 10:31 PM |
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look at the robin hood 2b kitcar site - the 2b uses the sierra rear end.
the main issue with the sierra IRS is the 'mounting donuts' tend to want to go inboard of the chassis where your hip wants to be. You will
see the mounting points on the 2b are recessed at that point, and the 2b is wider to allow it.
I dont think its impossuble - but would take some mod work.
atb
steve
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JoelP
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| posted on 13/1/04 at 10:46 PM |
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ive put the doughnuts about 6 inches behind my arse, hence the fact that the new car is longer wheelbase than the donor!!!
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stephen_gusterson
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| posted on 13/1/04 at 11:00 PM |
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I was originally gonna use the sierra irs - but doing as you said joel wouldnt have looked anything like an attempt at a morgan replica - the wheels I
guess would be about a foot too far back!
atb
steve
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