2CV Special - Final* CAD Design

[grizz]

Dec 31, 2020 14:12:47 GMT cb11acd said:

I said the end of this year and I am determined to stick to it.

So here is the plan.

January - finalise the last few bits of chassis layout (pedel mounting, engine position, occupant space). It is all currently within a close ballpark of correct I just want to mock a few bits up before commiting.

February - Begin welding chassis together. I will use the old Citroen one to pin down the new one to keep alignment and eventually move the chassis to a build table/platform to finish it off.

March - By the end of march I want most of the chassis welded together so I can start to fit the Citroen bits (suspension and steering)

April, May, June - Carry on fitting parts, and finish the chassis welding. At this stage I want a rolling chassis with the engine and gearbox in place.

July, August, September - I want a running but in no way driveable car. The gear linkage will need a lot of thought and I expect I won't be able to get it all done, but I want all of the systems in place to fettle with.

By December - A drivable chassis

Now wahat I need is the weight of the internet pushing down on me preasuring me to keep to schedule. Lets review this January 1st 2022 to see If I managed to stay on schedule (doubt).

So what will it look like? well I am now officially on revision 4 but in reality revision 84 as I am bad at keeping a revision history. Over the year it went from a single seat open wheel to 2 seat close wheel to 2 eat open wheel and now back to 2 seat close wheel design. I am keeping in mind the IVA test for headlight positions and chassis construction hence the flip flopping. I also want it to comfortable seat me and someone else my size (over 95th percentile) so packaging everything is a challenge.

This weekend I will confirm a few of the unknowns (listed above) and finalise the chassis design to order the steel. 

Liking this.

craigrk will probably stop by soon enough.

[Tazzy]

Awesome!

[spartacus]

That latest design looks great. I think you're doing the right thing making it a two seater, it'll give you more opportunities to drive it. Great to see you taking the 'long way home' too, it would have been easy (ish) to use a locaterfield chassis and put your own body on it, but where's the fun in that, eh?

[broady]

Fantastic idea! Well thought through

[cb11acd]

Jan 1, 2021 16:29:59 GMT spartacus said:

That latest design looks great. I think you're doing the right thing making it a two seater, it'll give you more opportunities to drive it. Great to see you taking the 'long way home' too, it would have been easy (ish) to use a locaterfield chassis and put your own body on it, but where's the fun in that, eh?

The two seater thing vs single seater thing has bugged me for ages. I am all set on 2 seater now but having a conversation with a fellow citroen specials person, they are interested in a similar single seater concept because of the pure feeling of freedom similar to a motorbike. I had about 10 seconds of 2 seater doubt before snapping out of it.

Small update, but I want to do more of them (for accountability if anything). I have messed around in the garage, checking interior space, pedel position, suspension mounting positions.

I have also ordered the steel for the chassis. I am also in the process of doing a few technical drawings just for my own reference and it means I don't need to keep going upstairs to the office. This should be done by the weekend ready to start cutting the steel chassis.

I am using the same wheelbase and track width as a 2CV, and will use the old 2CV chassis to align the new chassis for the early part of welding (kind of like a jig, it will be bolted down). Once the center sections have been welded I will move it to my "welding table" which is an old scalectrix track I claimed from work (a platform made from plywood, 8ft x 4ft). It will be fastened down and the rest of the flat chassis members welded on (in blue). When this is assembled, I am going to outsource the big tube bends locally (as I don't have a tube bender). I will confirm the dimensions after welding the flat base to ensure it fits (in red). After that all of the smaller chassis members will be welded to whats already there (in orange).

I have also drawn up a bit of a body tub, which is in the bottom render. This will have suicide doors because they're cool.

[ettorebugatti]

Clean render!

So the suspension is going to be mounted on the blue part of chassis?

I think a Cooper F3 500 style suspension with double wishbones and transverse leaf spring (maybe now we take it from Fiat 126 instead of a Topolino) and a deDion axle at the back would be very 50s sportscar technology.

Found some inspiration too:
www.britishracecar.com/CameronHealy-Cooper-Porsche.htm

[metroman]

[/img]

If you don't already have a copy I could not recommend having a read of this book more

www.ebay.co.uk/itm/Racing-and-Sports-Car-Chassis-Design-Michael-Costin-David-Phipps-Jaguar-Lotus/284098165960?hash=item422591fcc8:g:VP0AAOSw1rJfxAd2

[llwynogmon]

Looking good, I assume that the Rover Jet car must have been an inspiration for the bodystyle. Love it, looking forward to seeing it completed.

[cb11acd]

Have to admit, I can't say it was an inspiration. The front end will change, as will the rear. I am mostly happy with the mid section but it's missing detail like external hinges (MK1 mini style) hidden in the big ducts.

As for chassis stiffness, it is something that I care about, and some chassis members are still missing most notably at the front and rear. You have to keep in mind though that the suspension will be 2CV based so no matter how stiff I design it, it's never going to handle well. I am hoping that it will handle fun.

Also in a double wishbone setup the forces go through both an upper and lower wishbone. A stiff chassis is important to ensure the mounting points stay in place relative to each other to not effect geometry. A 2CV suspension has none of that, the front and rear are on leading and trailing arms with one big bearing on each corner. They are also completely rigid left to right. So even if the chassis distorted the handling characteristics wouldn't be too adversely effected compared to a double wishbone setup. Then if you compare the above to a standard 2CV chassis there will be a notable increase in stiffness.

Final point, the chassis was largely inspired by the proven pembleton design, which although incorporates a stressed skin construction will be somewhat less rigid than the above.

[ettorebugatti]

I found this while browsing, apparantly Cooper designed a sports car themselves. Th Cooper-Triumph T4.
Looks quite French with the disc wheels and blue paint.


500race.org/marques/1947-mk-i-t4/

[kevins]

Looking good, one suggestion would be to brace the roll hoops rearward down to the chassis, they won't provide much protection as they are, you could make it a bolt in section to pass through the body if you wished to.

[cb11acd]

Made some progress. Started to weld the base chassis lengths (mostly tacked for now). The 2 main chassis legs, and the braces inboard where welded while bolted to the old chassis. Bit of extra work but it has meant it came out completely flat front to back, and a bit of deflection left to right which I should be able to weld out when I do the underside. 

Not the best pictures, doesn't seem to like the camera. I plan on outsourcing the tube sections. There is a local place and it's quite simple so shouldn't be too much. 

If it is a lot of money, I have a 2nd design that doesn't require the tube bending.

[greencarfritz]

With not using a 2cv chassis or engine anymore are you designing this with the IVA as top priority?

[cb11acd]

Yes this will have to go through IVA. If I used the 2cv engine I could sneak through an MSVA if I kept the weight down to under 400kg. But as the engine is more than 25hp (I think that's the limit) it will need the full IVA.

[cb11acd]

Just a small update. 

I have had a bit of a nightmare with my CAD software. Nightmare being my license expired, and I can't renew it until April. I sort of knew this was about to happen and so my final act was to produce enough 2d drawings to keep me going. 

One other progress is that I had the chassis tubes bent. These were done locally and I picked them up on Friday, they need a bit of fettling but nothing major. I did need to get a bit creative putting in the angled cuts though. 




Then proceeded to tack a few bits in place so I can see how it all sits in real life rather than on screen. It's going to be a tight fit length wise, there isn't too much space between the axles if you want to sit low to the floor. 







Next step is to fit the pedel pieces that will support the pedels and then work out a seat mount/ position. I have a few ideas for this, some more experimental than others. I should probably keep it simple and go for something like an aluminium bucket based on a lotus Europa. 

[Frankenhealey]

Another 2CV special spotted on Faceache

[mr2fc]

Could someone with Facebook message them and tell them not to paint it!?

Thank you!!!

[cb11acd]

Another small update, or rather a dilemma. It would be good to get the hive minds opinion on.

The engine, as designed, overhangs the suspension arms. It is pretty close too, I was hoping I would get away with it, and in CAD it looked close but acceptable (But I only had the newer BMW engine in CAD, not this one). I pretended this wasn't an issue until now but seeing it pushed together I am not happy with the clearence.





So my dilemma. I can raise the engine and gearbox up, rasing the CoG and it might clear the suspension arms. I am not widening the rear or designing my own arms as that will be too complicated (this project has gone on for too long already). OR I can spin the engine and box around and make it rear engined. This simplifies a whole lot like engine mounting, gearbox linkage, clearence for exhausts, rear axle won't need modification and I can lower the CoG. BUT, it won't be what I set out to achieve, moves the weight rearward which would compromise handling (not like the car was ever designed to handle).



Right now, I am leaning towards rear engined. Also with the engine not actually weighing that much it probably won't make a whole load of difference. I plan on using a cut up gearbox at the front for the front brakes anyway (and I am considering some kind of energy recovery system/motor at the front).

What do you all think?

[Darkspeed]

How do you resolve the drive direction in rear engine?

ETA

What’s the wheelbase?

[cb11acd]

Mar 8, 2021 19:43:05 GMT Darkspeed said:

How do you resolve the drive direction in rear engine?

ETA

What’s the wheelbase?

You can flip the diff. Shouldn't be insurmountable, the 2cv Sahara had a flipped gearbox/engine in the rear.

Wheelbase remains the same as a 2CV. Track will be a tad wider as it will be non standard wheels but not much.

Wheelbase: 2400mm
Track width: 1260mm ish