Homemade CFRP mid engine sports car

[Neil]

update on progress into 2024 .. it didn't start very well, with Covid followed by Pneumonia i basically lost all of January

I'm better now and I've been working on two things, designing the suspension uprights and building the seats. For the seats i need to make my own because off the shelf ones won't fit, and also because why make things easy ..

I've been building a pattern of the seat from wood/cardboard/plaster/body-filler. Nearly done now, then will take a glass fibre mould, then will make some CFRP seats via vacuum infusion. The seats will be fixed to the body, i intend to use adjustable pedals rather than adjustable seats.

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Are you looking for front or rear uprights? -Neil

 

[Joel K]

Glad you’re feeling better, always look forward to your build updates. Keep up the great work!

 

[Paul Bristo]

Are you looking for front or rear uprights? -Neil

Both Neil, my suspension is my own layout so i need to fabricate some. I have designed some that i'm looking to get waterjet cut

 

[Neil]

Both Neil, my suspension is my own layout so i need to fabricate some. I have designed some that i'm looking to get waterjet cut

Paul, I listed a pair of GTP rear suspension uprights that you may find by using "search".

As far as front uprights are concerned, the Ford Mustang II front suspension geometry is very popular with home builders for good reason- the geometry is excellent. This suspension was designed by Chuck Weiss when he was at Ford Motor Company. I had the opportunity to discuss this design with Chuck many years ago and I selected it for my black Mirage race car. Although I built the car to the SCTA (Bonneville) rule book, it is fully capable of acquitting itself nicely on a road course.

The rear suspension is my own design, using Porsche 996 rear uprights and Porsche 928-S4 brake rotors & Brembo calipers. This video may be helpful:

I used "Suspension Analyzer" software to analyze both F & R geometry.

 

[Neil]

Both Neil, my suspension is my own layout so i need to fabricate some. I have designed some that i'm looking to get waterjet cut

Suspension geometry is a VERY complex subject and without the capability of computer analysis, it can go horribly wrong. Considering how much we all spend on building our projects, the cost of good software is a price we pay for not winding up with an ill-handling project. Lots of factors such as caster angle, wheel width, or anti-dive add to the difficulty of designing a good suspension.

 

[Paul Bristo]

Thanks Neil, agree with you 100%. Computer analysis is my day job so this is something i'm comfortable with, in fact its a little bit one of the reasons behind my build - I spend all day developing cars only in the virtual world so this is my chance to satisfy my desire to get my hands dirty. Once i've finished this body and chassis work (i.e. structural work) i'm leaving my comfort zone behind, areas such as hydraulics/fuel systems/cooling/electrics/engine&transmission etc will be quite new to me so all advice with them is very welcome !

 

[Neil]

Thanks Neil, agree with you 100%. Computer analysis is my day job so this is something i'm comfortable with, in fact its a little bit one of the reasons behind my build - I spend all day developing cars only in the virtual world so this is my chance to satisfy my desire to get my hands dirty. Once i've finished this body and chassis work (i.e. structural work) i'm leaving my comfort zone behind, areas such as hydraulics/fuel systems/cooling/electrics/engine&transmission etc will be quite new to me so all advice with them is very welcome !

 

[Neil]

I neglected to add that although I used the Porsche 996 five-link geometry in the rear of my black Mirage, I found that it was a bit "off" so I modified it a little to make it better. I suspect that Porsche specified those suspension pick-up mounting points to compensate for their rubber bushing compression under load. I used all spherical rod end bearings so compression was not a factor for me..

 

[Paul Bristo]

Finished off the seat mould and made my first seat, after trimming the edges it mostly fits in the car - phew !

Next I need to make some brackets to mount it to the tub. I'm going for a fixed seat and adjustable pedals. I also need to sort the seatbelt anchorages, i'm going for a 6 point harness.

At some point much later in the project i'll make some padding/upholstery for the seats, but i'll leave this until all the messy stages are finished.

 

[Paul Bristo]

got the first seat in, aside from an annoying problem from a spinning rivnut it went pretty easy.

First i got the seat sitting at the correct position and angle. This was done by first sorting a bracket to the rear bulkhead to set the max longitudinal position (not fixed yet just resting against the bracket), then attaching a bracket at the very front tip to set the height at the front. Once placed in the car, i rotated the seat about these two points until the correct inclination, then measured gap between lower rear and the floor. Then made a suitable sized bracket for this and attached to the seat and put back in the car. Now the seat sits on 3 points of contact at the right position+angle. Next step was to fix the brackets to the seat, apply glue to the underside and carefully place in the car. Once set, unbolt seat from brackets and securely join the brackets down with rivets. Additional brackets added later to support the thighs and calfs were added in a similar manner.

Next, brackets for securing the harness eyelets to were moulded (3d printed mould, wet layup, vacuum bag), then bonded and riveted in place

now i get to do it all again I've already moulded all the parts for the RH side and having done it once already hopefully it should be quick.

 

[Paul Bristo]

Got two seats in now ! and they successfully passed rigorous testing by my little helpers.

Am fabricating my suspension uprights right now, will post some photos of them soon, and in the background am thinking about the steering and IP.

 

[Davidmgbv8]

Have you decided on a drive train yet? Still voting for a wicked turbo diesel that wisks you along and gets 40mpg.

 

[Paul Bristo]

Have you decided on a drive train yet? Still voting for a wicked turbo diesel that wisks you along and gets 40mpg.

Plan A is still some form of V8 crate engine and whatever suitable transaxle i can find to mate it to
But .... occasionally i dream about V10s and V12s, i even think they would fit.
I'm very wary of the fact that this is going to be a slow build and the world is changing, so am holding off on any of this for a bit so i don't get stung by any IVA requirement changes.
TBH i've never been a diesel fan but never say never!
I suspect it will all likely come down to what's available and within budget in a few years time

 

[Neil]

Plan A is still some form of V8 crate engine and whatever suitable transaxle i can find to mate it to
But .... occasionally i dream about V10s and V12s, i even think they would fit.
I'm very wary of the fact that this is going to be a slow build and the world is changing, so am holding off on any of this for a bit so i don't get stung by any IVA requirement changes.
TBH i've never been a diesel fan but never say never!
I suspect it will all likely come down to what's available and within budget in a few years time

Paul, choosing a V10 or a V12 is like signing up for a beating.

 

[Brian]

Electric motors, but instead of a huge bank of batteries, a small bank and a gas turbine generator? Might make AWD an option.

 

[Andrew Robertson]

2009 Audi S8 5.2 FSI quattro | Trade Me Motors

Super tidy inside and out, small scrape to lower left side of the front bumper that has been touched up but hard to see. Probably no more than 4 small stone chi...

www.trademe.co.nz

USD $14k for 5.2V10 + Transaxle + free car? Are these common and cheap where you are?

 

[Paul Bristo]

2009 Audi S8 5.2 FSI quattro | Trade Me Motors

Super tidy inside and out, small scrape to lower left side of the front bumper that has been touched up but hard to see. Probably no more than 4 small stone chi...

www.trademe.co.nz

USD $14k for 5.2V10 + Transaxle + free car? Are these common and cheap where you are?

that's an interesting option Andrew

i've always been a worried with this kind of route with what to do with the engine electronics and immobiliser, whether its at all possible to lift all the control units as one and use them, or whether i'd need to go down an aftermarket ecu direction.

 

[Paul Bristo]

Going to update you all with the uprights i've been working on for the last few months

Plan A was waterjet cut aluminium parts but the quotes i was getting were rather more than i wanted to pay ..

so plan B was for me to cut the exact same parts out myself (very slowly) on my DIY CNC router, which started out ok but my machine broke down after completing just 1 upright set ...

so then plan C was born, which was to make them instead from lots of left over carbon fibre and high temp epoxy. I've not gone very lightweight with them, but at this point this was the easiest way forward for me with the materials i had.

step one, 3d printed mould. due to the size of my printer this involved several segments being printed and them welded together with an old soldering iron. For the front uprights there's also some aluminium inserts prepared for mounting a steering plate and for the ball joint tapered holes. These are held in position on features in the 3d printed mould.



step two, add lots and lots of plies of carbon fibre and high temp epoxy, vacuum bag it and cure and room temp. demould and drill out the holes. This step puts down 80% of the total material and took me about 3 hours per upright.



step three, need to mould the inside surface now. I need to add stiffening ribs in some places and in other places i need a perfectly flat seat area for bolt heads to sit against. So i glue in some foam for ribs and bolt in some 3d printed shapes to form the bolt head seats. Then add lots more plies of carbon fibre, tighten the bolts in the 3d printed shapes, and vac bag it again.



step four, trim the edges, re-drill the holes, and sand it all down. make sure everything fits. Then post cure it in the oven. Used the kitchen oven for this and it took about 15 hours so i did need to ask the wife very nicely beforehand !



step five, assemble

 

[Neil]

Going to update you all with the uprights i've been working on for the last few months

Plan A was waterjet cut aluminium parts but the quotes i was getting were rather more than i wanted to pay ..

so plan B was for me to cut the exact same parts out myself (very slowly) on my DIY CNC router, which started out ok but my machine broke down after completing just 1 upright set ...

so then plan C was born, which was to make them instead from lots of left over carbon fibre and high temp epoxy. I've not gone very lightweight with them, but at this point this was the easiest way forward for me with the materials i had.

step one, 3d printed mould. due to the size of my printer this involved several segments being printed and them welded together with an old soldering iron. For the front uprights there's also some aluminium inserts prepared for mounting a steering plate and for the ball joint tapered holes. These are held in position on features in the 3d printed mould.

View attachment 140663

step two, add lots and lots of plies of carbon fibre and high temp epoxy, vacuum bag it and cure and room temp. demould and drill out the holes. This step puts down 80% of the total material and took me about 3 hours per upright.

View attachment 140665View attachment 140666View attachment 140667

step three, need to mould the inside surface now. I need to add stiffening ribs in some places and in other places i need a perfectly flat seat area for bolt heads to sit against. So i glue in some foam for ribs and bolt in some 3d printed shapes to form the bolt head seats. Then add lots more plies of carbon fibre, tighten the bolts in the 3d printed shapes, and vac bag it again.

View attachment 140668

step four, trim the edges, re-drill the holes, and sand it all down. make sure everything fits. Then post cure it in the oven. Used the kitchen oven for this and it took about 15 hours so i did need to ask the wife very nicely beforehand !

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step five, assemble

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What will happen to the CF resin when your rear rotors are glowing red hot. What is its glass transition temperature, Tg?

 

[Paul Bristo]

What will happen to the CF resin when your rear rotors are glowing red hot. What is its glass transition temperature, Tg?

Tg is 200 celcius. I plan to add a heat shield to protect against radiation from the rotors, plus some brake cooling ducts to keep them cool. Conduction through the hub is a worry, but indicative data shows 200 degC should be enough.

Temperature is the reason why this was plan C. My plan is to monitor via thermocouples when i get it running, if its an issue i can always go back to an aluminium route.