BACON
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| posted on 6/1/12 at 07:24 PM |
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Modifying a chassis
Hi everyone, I've been looking through this site for years admiring all the scratch builds and wishing I could do something similar myself but I
don't have any of the required skills or brains! Ideally I would love a kit car where all the figuring out was already done and all I had to do
was bolt it together, but the only one I like is the ultima and thats WAY out of my budget!
But I've been doing some scheming and researching and I've come up with what I think is quite a good plan.
To carry out my idea I need a midtec spyder kit or (complete car preferably) then cut it in half! No seriously... I want to increase the wheelbase by
about 300mm to suit the bodywork I plan on fitting and also if it is stretched in the middle cockpit area, where I figured it would be easiest to cut
the tubes and weld longer ones in, then i would actually be able to fit it it comfortably (I'm 6'3"
Firstly, could this be done relatively easily?
Secondly, will it weaken the chassis? I also plan on having a full roll cage welded on too so this would help stiffen it up a bit more.
Thirdly, how would it affect the handling? I thought as it was a bit longer it would be more stable??
Anything I've missed out?? I've been so pleased with myself the last few days because of my idea so go easy on me!
thanks
Jon
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macc man
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| posted on 6/1/12 at 07:51 PM |
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The phrase cut & shut springs to mind. I would be very wary of this approach. Best to find a car that fits you.
[Edited on 6/1/12 by macc man]
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zilspeed
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| posted on 6/1/12 at 08:05 PM |
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If it helps, I'm 6 foot 2.
Standard Locost, I don't fit with a seat in the car, have tot ake the seat out.
MK Indy, I do fit.
Sylva Leader I do fit.
There's lots of tall blokes who do fit in tiny little kit cars without having to stretch them.
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MikeR
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| posted on 6/1/12 at 08:06 PM |
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i see no problem. Its just like me making a mistake on my chassis and replacing a weld or repairing some crash damage. Lots of people have had new
front ends after a crash. The issue is lengthening the chassis and can it take it. Adding the full cage will help but i'm not familiar with the
design - do you have any photos?
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MikeR
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| posted on 6/1/12 at 08:28 PM |
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just seen the previous post. i'm 6'3 and fit in a locost using a home made foam seat.
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wilkingj
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| posted on 6/1/12 at 09:08 PM |
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Paul (Notts) is selling his Viento at a very reasonable price, You will easily fit in that.
Its a good car. OK, not a Middy, but a good car all the same.
Linky
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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BACON
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| posted on 6/1/12 at 11:50 PM |
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Yes it does sound a bit cut and shut, but if the tubes are cut where they were welded originally and replaced with tubes 300mm longer would there be a
problem?
Some people seem to be missing the point, I'm after a chassis to fit a particular set of gt style bodywork that I might be getting a deal on, so
it's got to be middy.
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Uphill Racer
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| posted on 7/1/12 at 12:27 AM |
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quote:
Originally posted by BACON
Hi everyone, I've been looking through this site for years admiring all the scratch builds and wishing I could do something similar myself but I
don't have any of the required skills or brains! Ideally I would love a kit car where all the figuring out was already done and all I had to do
was bolt it together, but the only one I like is the ultima and thats WAY out of my budget!
But I've been doing some scheming and researching and I've come up with what I think is quite a good plan.
To carry out my idea I need a midtec spyder kit or (complete car preferably) then cut it in half! No seriously... I want to increase the wheelbase by
about 300mm to suit the bodywork I plan on fitting and also if it is stretched in the middle cockpit area, where I figured it would be easiest to cut
the tubes and weld longer ones in, then i would actually be able to fit it it comfortably (I'm 6'3"
Firstly, could this be done relatively easily?
Secondly, will it weaken the chassis? I also plan on having a full roll cage welded on too so this would help stiffen it up a bit more.
Thirdly, how would it affect the handling? I thought as it was a bit longer it would be more stable??
Anything I've missed out?? I've been so pleased with myself the last few days because of my idea so go easy on me!
thanks
Jon
All your questions have to be qualified by how competent you are?
First..........yes
Second.........yes it will weaken it. A well designed full cage should add strength.
Third..........was it not stable to start with?
A longer wheelbase will make the car slower to turn but that is horses for courses, depends on its use.
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BACON
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| posted on 7/1/12 at 12:51 AM |
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I'm not at all competent! No I wouldn't do the welding, I would either get it gone by an engineering company or ask my friend who is a
welder/fabricator by trade to do it. I just think these crazy ideas up
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Theshed
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| posted on 7/1/12 at 10:43 AM |
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Why not! If you avoid welds in the middle of tubes there should be no insurmountable issues. Some care will be needed to keep things straight. There
will be some loss of strength caused by the stretch but you could make up for that by using bigger tubes (best) or thicker tubes (less good) or adding
more tubes - as you will be doing with your roll cage. I can see that you would save heaps of time not designing your own suspension mounts etc.
The handling will be affected. A longer wheelbase will (all other things equal) be more stable in a straight line but worse on turn in. Do you really
need an extra 300mm? Seems a lot for a couple of extra inches of height.
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designer
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| posted on 7/1/12 at 11:41 AM |
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Done right and 'professionally' welded it should be OK. Personally, I would add gussets to and reworked joints.
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BACON
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| posted on 7/1/12 at 04:53 PM |
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That's more like what I wanted to hear
Thinking about it I'd much rather an engineering company did it as I'd like it to be straight afterwards. Do you guys know any companies
in the norkolk area who would be worth phoning? One such company I've seen in ppc magazine is wisbech engineering, anyone know of any others?
The reason for the 300mm extra is that I have a full gt style body that I have in mind fitting, the midtec is about 300mm shorter in wheelbase than
the car the bodywork is off and only a little bit narrower ( figured that could be sorted with lower offset wheels?)
Keep the feed back coming
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britishtrident
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| posted on 7/1/12 at 06:12 PM |
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It isn't that difficult to do and keep it straight but be aware of the legal aspect as it invalidates the cars SVA/IVA.
Of course unlike a stretched tintop limo it is not likely to come to the attention of the powers that be.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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BACON
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| posted on 7/1/12 at 11:28 PM |
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I though it probably would need another sva/iva after the modifications were complete, but as it is going to be track biased I wasn't going to
worry about it too much until I wanted to make it road worthy.
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GRRR
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| posted on 8/1/12 at 08:32 PM |
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Bigger offset wheels could have an effect on the suspension setup as it moves where the centre of the tyres contact patch is relative to the
suspension pickups. I think it was on this forum some guy did an analysis of a Ferrari where fitting bigger/different wheels promoted lots of
under/oversteer.
Also changing wheelbase could affect balance of the car as the roll axis would be affected maybe?
How serious is it as a track car? Just some fun then probably not an issue but if its competing then revisiting geometry would be a good idea.
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motorcycle_mayhem
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| posted on 8/1/12 at 09:14 PM |
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There really (in my opinion) isn't a problem here. Simply add a longer member, or two, retain any triangulation at the (new) joints. Take a step
back and look, if something isn't right, it probably won't look right.
I shortened a westfield chassis, front scuttle to front of car. Reason was simply that the V-twin engine (TL1000) left so much room it looked silly.
Shortened wheelbase made the car quite lively...
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BACON
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| posted on 8/1/12 at 10:23 PM |
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Having had another look at the track dimensions they are very similar, the front of the midtec is 4mm over and the rear is 100mm under. The midtec
track is the same front and rear. I'm not sure what size wheels the midtec was specced with but the ones on the car I'm trying to
"replicate" are 8.5 wide at the front and10.5 at the back.
I don't think it would ever see competition use (as much as I'd like to!) but I do want it to be stupidly fast on track. I've been
used to driving hot hatches and a BMW e36 as a track car, I like to think I'm a reasonably good driver but I'm always left standing by
well driven spaceframed cars, just wanted to take my type of track car to the next level.
So yes, pin sharp handling is important to me.
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