Tube Chassis "VW Caddy" Project

[43655]

Hello all;
Welcome to my project!
It started off as tidying up my '88 VW Caddy, but I got fascinated by motorsport design and engineering at the same kind of time, wanting to ditch the ancient-tech leaf springs for 4-link axle etc, then toyed with a mid engine setup, bought a gearbox and subframe etc from an Audi 80 to suit.

Fast forward a few months, the caddy is now only going to be used as a buck for taking GRP moulds off.
Much to the dismay of the VW Caddy Forum
It will have Audi Quattro-style arches and 'side skirts' to bump it out to 1850mm wide (to match the Ultima GTR)
Mid engine 2.7T V6 mounted to an 01E DQS 6 speed gearbox
I have designed a full tube chassis for the car, as well as plotting front and rear suspension geometry, uprights etc

At the time of writing I'd say the CAD designing side is about 90% there and the chassis fabrication has started
So, photos:








(model is pretty crap, I can't do surface modelling)

This is my first attempt at bot designing and making something of this magnitude.
I welcome criticism and suggestions, as I know there are many much more knowledgeable people on this forum!

[43655]

Some pictures of the actual building

Engine and 'box temporarily mated together

2.7t V6 ARE engine and DQS code 01E fwd box

cutting


Welding


welded


This so far is the lower cab area, and the bottom front wishbone mounting area
I'm using rectangular (50x30x2 mostly) as all these faces will have panels bonded on to increase strength
Final weight for the chassis alone comes out around 110kg, while it's no lightweight it should be stiff and safe

[43655]

thanks guys, much appreciated.
with regards to the wishbones, the front uprights have shim-based camber adjustment, have not yet decided about caster
Was going to just go for somewhere around 8 degrees as a starting point, then if i want to change it make up some new upper wishbones
Seems a bit expensive and time consuming I know, but as i'm planning to use delrin bushes instead of rose joints it's a bit more complicated
maybe I will use rose joints for the UCAs...

[43655]

...there was a PVW article?

[43655]

ah goodness no, mine is a complete tube chassis, bodywork will be muuch wider than standard.
There are 2 so far that I know of actually.
Really wanted to get into contact with the builder about the emerald ECU he went with, as I may be going down that route.
I hate engine work though so getting the engine running is something i've been avoiding thinking about a bit
Mine currently looks lie this

[43655]

Interesting, not seen that before. I quite like the wider look next to a standard MK1
What are you suggesting though?

[43655]

Oh, nah I like arches
The S1 Quattros are one of my biggest inspiration, especially the insane KRB one

But this is to be a road legal car, so plastic windscreen would be out of the question. a custom windscreen would be very expensive!

[43655]

rear end now has the 'suspension box' done, and the main linking tubes


still only mobile phone photos i'm afraid, but have a decent camera on order!

Still not decided on whereabouts to mount the rear suspension yet, and working on designing the uprights still too.
It's getting pretty cold wet and miserable now for working on the chassis, so maybe move onto wishbones and such soon

[43655]

Clive, first of all I have read through your build so many times, I'm honoured!
Also many thanks dom9 for the kind words, I have big expectations to live up to!

I'll be using bolt-on hubs for the rear definitely, as I need the driveshaft splines, will be using standard Audi A6 hubs and driveshafts (I think the track is quite close)
I'm doing my best to keep weight down, so hadn't considered the bolt-ons much as the ones I have are pretty heavy
However not really considered heat expansion much, do you know what kind of temperatures they would be subject to?
Had thought that aluminium brake bells and possibly even aluminium hubs would have helped dissipate heat from the rotor

Have been looking at all sorts of bearing configurations, most recently using large diameter taper bearings, but sealing them is a pain.

current design



As for the chassis, have a better camera now, and managed to move it to take some better photos


now had the rear 'up' diagonals made and welded in

[43655]

Thank you, means a lot coming from someone who does this professionally!
For me it's only a hobby at the moment I guess, but probably something i'd like to be doing in the future

Progress hasn't been that quick but the design stage has and still is taking a lot of time and effort!

Bit unfortunate about hearings in ally being a no-no, but on the advice of yourself and Clive I've done some more work on my upright design



Steering arm is a bit temporary, drew it up in work

bumped the webs up to 10 to bring them close to the caliper mounts as suggested.
the caliper there isn't final at all, just what I could get a model of from GrabCad!
So the dimensions may change, depends which brakes I can afford.

Weight wise I'm quite happy with the body of it but the hub itself bearing and housing are heavy, have one in the kitchen.
So I may well go with turning my own hubs and bearing carriers, becuase i was pretty short of work on this project anyway

Edit, 3D view and downloadable from https://grabcad.com/library/front-upright-aluminiu...
Model for exploded and regular assembly for anyone interested

Edited by 43655 on Tuesday 2nd December 22:43

[43655]

Italo, Thank you

All the design work is done in Solidworks 2014, the Weldments feature makes designing tube structures really easy!
Version 1 of the chassis took me about 4 hours to knock up

It's all MIG welded I have a second hand Cebora Autostar 190, a decent TIG at ~£1500 is a bit out of my budget!
I'll be TIG welding the wishbones though, as I can do them in work
Each has it's pros and cons really

Edited by 43655 on Saturday 6th December 12:22

[43655]

Ebo100 said:

Forgive my ignorance here, but after the problems that bnracing mentioned why manufacture your own uprights and wishbones (unless you want to scraatch build everything of course)?

Wouldn't it be better to take an existing set up like the VX220 / Elise series 2 where you have access to numerous second hand parts, known geometry values, all things like the calipers, discs, bushes, shims and ball joints readily available.

It seems like you making work for yourself. Especially after the link to the wide bodied Golf stated that it was awful to drive

I wouldn't consider them problems, I have taken his and Clive's advice and modified to suit and now have a better part.
Anyway the suspension geometry has been plotted out, I have a much wider ball joint separation than most stock uprights and there isn't that much that's suitable.
The beauty is that by designing upright geometry wishbones and chassis together is that I'm not having to work with any particularly compromising element in theory.
That said at least you didn't suggest using standard kit car part. Rod ends in bending is all i need to say, and they bloody love them too

Could I have used parts and geometry off another car sure, I know of a few similar projects done that way (Lasupra and ETS Hilux spring to mind)
Not to be assuming I know better than Lotus engineers but what's to say that they're really that good?
In fact why bother building a car when you could just buy one?
Maybe I should have just taken out a huge loan and bought an Ultima or something?
(I'm 22, and building this with ~£16k per year income)

Nah, I'm a designer, and wannabe-fabricator, so for me this is a design project, an engineering project, and generally an hell of a learning experience.
I'd love to get to do something like this professionally one day, so this is my way of educating myself I guess.

With regards to the golf, I'm not surprised it sucked, it's short, very light rear, RWD car, with a huge V8 dumped in the front.
Sure it's a VW-scene wet dream, but this is completely different, don't you think? Apples-and-oranges

The only think VW about it will be a very vague resemblance, what with the widening, shortening and general chopping up.
Sure it's a rubbish body to use really, but it was MY car.
It will be more Ultima or GT40 than it will ever be VW though!

Anyway I certainly hope i can make a car that handles well, mid engine is common and proven, chassis should be pretty stiff and safe, and I've spent most of my free time in the last few years researching, reading others' builds, saving photos etc

Edited by 43655 on Monday 8th December 21:20

[43655]

Ebo, Thanks I hope so! I've done a lot of revisions and reworking on it. Still tweaking it now.
Not done much recently, got college and crap weather to contend with.

Good good, and thanks for the feedback. I'm not sure yet if I'll use OE hubs of some sort, or just make my own. Lot of work, but could also spend a lot of time looking for the right sized hub. Will almost certainly make the bearing carrier myself, but going to look into using a water-jet plate and machined tube and weld them together rather than machining from solid.

As for the wishbones, there shouldn't really be any twisting force surely? lateral forces fed straight into the pivots at the chassis end, and some bending force from the mounting of the pushrod, but i'll make that as near to the spherical bearing as i can.
will do something like this, although maybe not with the nice swaging, lot of work to make a tool for 2 wishbones!

[43655]

Sorry for not updating this in months, it got forgotten about a bit!
Not done anywhere near as much as I'd like, other hobbies, dislocated shoulder and my daily volvo dying are among the excuses

So, what have I done...
Spent a lot of time on the CAD side, re-re-designing mainly the rear suspension/chassis area, happy enough with it and got that made.
Measured up and had the 'roll cage' sections formed, then re-measured it and had the front section made again, oops.
Decided I won't be happy using the Audi 01E gearbox, as it would put the sump some 5" off the bottom of the chassis, not cool!


Especially as Audi went to the effort of putting a real nice slimline sump on it, with the steel block, twin turbos and general over-engineering (30 valves!) it's a weighty beast that I'd like as low as possible.

What else have I done, leaning towards aftermarket ECU as I want traction control, and the ability to have antilag, flatshift etc, but its all money
Plus maybe one day I'll consider a twin turbo v8...

As it is the chassis looks really high compared to GT40/Ultima/GTMs and so forth. On the other hand it's considerably lower than a stock caddy still

But whatever.

Picture time

[43655]

To my horror, realised I hadn't allowed any clearance at all in the lower bearing of the upright for steering and suspension movement!
Ended up going to a singe-shear setup instead which is a bit of a shame as it's worse engineering practice.
Made up for it by using a custom 3/4" Ti6-4 pin with an integrated safety washer