cymtriks
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| posted on 22/5/03 at 08:24 PM |
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tube R for V8s
Tube R is the only diagonal across the top of the engine bay and is important to the chassis stiffness.
Using two short R tubes as described earlier in this thread reduces stiffness from about 1200 to 900 ftlbs for the book chassis and 2500 to 1950 ftlbs
for my modified chassis.
A better solution for wide engines may be to replace the top side tubes from the footwell ends to the chassis front by ladder frame sized tubes of 4x2
with 14g (2mm) wall. These tubes should be fully welded into the footwell ends which should also be in 14g welded in sheet. Replace the two short tube
Rs with boxed in 14g sheet braces making, roughly, a 45 degree triangle, four inches deep, across the width of the footwell ends.
It is heavier and more difficult to make but the chassis stiffness should be good and the V8 will easily compensate for the extra metal.
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craig1410
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| posted on 22/5/03 at 08:32 PM |
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Cymtriks,
I wondered when you would come to the rescue 
Unfortunately you've not given me the answer I was hoping for (ie. a simple one)
Well I suppose you have and you haven't really, I just wish I'd asked the question before I built the front of my chassis!
Should the 4x2 be oriented long edge vertical or horizontal?
By the way, what sort of stiffness would something like a Mazda MX-5 or MGF or Z3 have to put things in perspective? I know the Elise is in a
different class altogether so I'm not going to try to match that (7000lbs or something I think?)
Thanks,
Craig.
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elewayne
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| posted on 23/5/03 at 12:41 AM |
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250 pounds
That 250 pounds thing was clearly one of the several misprints, it was supposed to read 2500 pounds, I think.
I was tring for $5000 US. I almost have a roller at this point and I added up my spread sheet the other day and found myself at $4600 already.
Looks like it might hit $10,000 before I'm through. Why did I start this anyway.
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macbrew
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| posted on 23/5/03 at 07:58 PM |
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One small comment certainly gets the discussion going. No offence to anyone just lively banter.
Thanks for the advice craig but it all got sorted a few months ago .. MK hub adapters and longer bottom wishbones.
Don't lose any sleep about my finances, the shoestring budget is a goal not a restriction I'm just trying to see what it can be done for.
Target is £1500. It will be a slow build because I'm making (rather than buying) everything I possibly can with limited tooling. My comment
about the book title is that it's 20 year old and the second edition should have taken into account inflation and the un-availablkity of MK2
Escorts rather than misleading people.
Yes I did research this project, my point is that it is impossible to do research to find out the real cost without first buying the book .... Catch
22. If you go ahead fine, if you dont £18 down the drain.
Good luck with your build .. sounds like a beast, wish I had the balls.
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Alan B
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| posted on 23/5/03 at 09:03 PM |
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Where do you get 20 years from..?
The first edition was published in 1996...
(I doubt the 250 was realistic then)
Or am I missing something?
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stephen_gusterson
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| posted on 23/5/03 at 09:50 PM |
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I have edition one.
it was first published in 1996.
Most people dont read and understand the trick in the wording
its called :
Build your own sports car for AS LITTLE AS 250 pounds.
you could say 200 or 20 or any number you wanted.......its all bollox anyway.
bit like writing a book called travel the world for 250 quid. Its easier if you have big tits, and in Rons case, the 'im a schoolteacher and
author - can you help with free stuff' approach
atb
steve
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macbrew
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| posted on 24/5/03 at 05:53 PM |
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Must admit I had no idea when the first edition was published, I guess it was written a few years before. Some of the pictures in the book look like
they came from the 60's.
I said 20 yrs cos that's when the last MK2 came of the line ... approx. my doner was a "W" one of the last I think.
Keep it comin I'm ard as butter.
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kiwirex
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| posted on 25/5/03 at 08:25 AM |
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cymtriks tube R for V8s vs Luego Viento
A salute to cymtriks, wizard of structural analysis. 
I was looking at the Luego web site the other day and some pics of the Viento. It looks like it has dual diagonals on the side of the engine bay.
I.e. TR2 from bottom of H to top of FU2 (as in the book), but looks like one from TOP of H to bottom of FU2.
My limited ability to visualise (and total lack of 3d software) hints that they might not intersect.
I think (from a hazy memory of a post from Luego themselves) they're using 2x1 for the diagonals.
If you've got a minute - and it's not stepping on Luego's toes - what effect would that have on the rigidity of the chassis?
Thanks,
Greg H
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cymtriks
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| posted on 27/5/03 at 10:29 AM |
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double tube TR1&2
It took a while to find that picture on the Luego site!
Two tubes in an X will increase the stiffness of the front. I have been updating my model of the lowcost to include the rear luggage area and to get
better esults for the flex in the rear suspension mounts. The results so far suggest that the luggage area adds what the mount flex takes away.
I'll put in an extra tube TR to see what it does to the standard chassis as this is an easy mod to make to my analysis.
The Luego site states that their chassis was FE stresses by Cranfield Institute of Technology and the model checked against a real chassis before
conducting a series of modifications to improve the design. Exactly the right way to do it.
However there is no indication as to what changes this actually led to. There does seem to be a different standard for every chassis on their site and
the changes outlined in my mods don't seem to appear in any of them. The thicker tunnel tubes suggest an attempt to take the weight of the chevy
V8 rear end/gearbox mount. The X arrangement of the extra TR1&2 tubes will certainly help
If I was fitting a big engine I'd use my mods plus:-
1) an extra vertical half way down the engine bay side, in line with the engine mounts and run a tube from top of tube H to the bottom of the new tube
and from top of tube FU to the bottom of the new tube.
2) 2x1 inch tubes G1/2, C, E and F1/2 with the 2 inch side vertical. The G1/2 tubes will need to pass behind the lower wishbone mounts near tubes
FU1/2 befor joining the sides of tube E
3) weld in the footwell ends in 16g or 14g sheet.
4) extra diagonals from where P meets tubes n and o to the bottom of tubes H and the tunnel arch over tube B2.
5) beef up tube J1/2 down the engine bay sides by replacing them with 4x2 as peviously described or short R tubes (not as good) or short R tubes plus
increased width J tubes (2 inches wide or more).
Really big V8s may be better suited to a ladder frame, hot rod style chassis of 4x2 RHS in 14g or (thicker) 1/8 inch wall. Properly X braced and with
a decent tunnel, seat back and scuttle structure this could give a stiff structure only slightly heavier than the book frame and with a completely
open engine bay area for a big and wide engine.
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kiwirex
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| posted on 27/5/03 at 10:07 PM |
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Thanks for that Cymtriks
I'd like to do a small v8 (if I can find one for my money), so I'll look at doing what you suggest.
Appreciate it.
- Greg H
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