2CV Special - Final* CAD Design

[bstardchild]

Can't you modify the arms for clearance?

You are making a whole new chassis - clearancing the arms surely is possible

Which way does the BMW engine roatate?

[cb11acd]

Mar 8, 2021 19:49:47 GMT bstardchild said:

Can't you modify the arms for clearance?

You are making a whole new chassis - clearancing the arms surely is possible

Which way does the BMW engine roatate?

With the amount of work the arms do I would hesitate to modify them apart from to strengthen them.

I also want to stick to using as many 2cv parts as possible, if I start contemplating wider mountings, or modified/new arms I may as well put in suspension more appropriate to the application.

BMW engine rotates the same way as the 2CV, the BMW unit has been used in pembletons and other 2cv specials.

I could fit it mid engined if I modify the rear axle and bring the cylinder heads above the hinge point eliminating the clearance issue, however then the engine/gearbox may sit too forward of the drive line.

[bstardchild]

Mar 8, 2021 20:10:42 GMT cb11acd said:

BMW engine rotates the same way as the 2CV, the BMW unit has been used in pembletons and other 2cv specials.

So facing the engine the other way would mean the drive is reversed?

[cb11acd]

Mar 8, 2021 20:27:25 GMT bstardchild said:

Mar 8, 2021 20:10:42 GMT cb11acd said:

BMW engine rotates the same way as the 2CV, the BMW unit has been used in pembletons and other 2cv specials.

So facing the engine the other way would mean the drive is reversed?

Yes, so I would flip the diff in the gearbox. Not too hard I believe. Citroen 2cv Sahara had a similar setup for their twin engined car

[glenanderson]

Have you considered a twin engine setup? It would put more weight at the front.

I think you’re doing the right thing going rear engine rather than mid, those cylinders were way too close to the suspension arms. It simplifies the gearchange issue too.

[horrido]

I´d go rear engined. It´s not like the motor weighs much. Good for traction.
I think it should handle well.

[Darkspeed]

As the rear engine layout provides no real benefits over the original position in the front - and in fact adds a load of drawbacks. If not wanting the added complication that sticking with the mid involves I would go back to a front engine location.

Personally think it will handle like a sick 2CV with that engine slung out the back. I would personally double down and go full DWB IRS especially when going to all that expense and effort. You can then get a better wheelbase track ratio and make it handle and be a pleasure to drive quickly.

[horrido]

Mar 12, 2021 13:26:00 GMT Darkspeed said:

As the rear engine layout provides no real benefits over the original position in the front - and in fact adds a load of drawbacks. 

What actually are the drawbacks? Traction isn´t one of them.

I realise Porsche have spent 50 years or so engineering their way around any and all rear engined issues, but with such a low weight of engine, that´s barely even going to be behind the line of the tyres, will it really make much odds where it´s positioned? It probably weighs less than the driver.

[Darkspeed]

You would need to elaborate on what comparison you are looking for. As I am advocating a FF as the 2CV standard, the drawbacks with moving it all to the rear and turning it around to face the other way seem quite obvious. Whilst elaborating on that I would be interested to read your thoughts on how a 2CV suspended special with the engine slung out the back will handle well.

[legend]

Where are you doing the PHD? I think Darkspeed is onto something as there's half of feck all 2cv left so why not do something different at the back end....and at the front

[horrido]

Mar 12, 2021 19:38:06 GMT Darkspeed said:

You would need to elaborate on what comparison you are looking for. As I am advocating a FF as the 2CV standard, the drawbacks with moving it all to the rear and turning it around to face the other way seem quite obvious. Whilst elaborating on that I would be interested to read your thoughts on how a 2CV suspended special with the engine slung out the back will handle well.

Hey relax, I´m just asking a question. Mainly as I don´t see anything obvious about it and I thought you might have an insight. 
Guess not.

[legend]

the engine in the original place means that all the steering, brakes etc can remain as normal, so it's way less complication for you to re engineer it

I wonder if beetle or 944 trailing arms would be of any use and clear the bmw heads if you keep the engine in the back

[Darkspeed]

Mar 12, 2021 20:25:26 GMT horrido said:

Mar 12, 2021 19:38:06 GMT Darkspeed said:

You would need to elaborate on what comparison you are looking for. As I am advocating a FF as the 2CV standard, the drawbacks with moving it all to the rear and turning it around to face the other way seem quite obvious. Whilst elaborating on that I would be interested to read your thoughts on how a 2CV suspended special with the engine slung out the back will handle well.

Hey relax, I´m just asking a question. Mainly as I don´t see anything obvious about it and I thought you might have an insight. 
Guess not.

I am horizontally relaxed - I thought my reply perfectly straight forward and without any emotion you seem to imply exists. I was just trying to establish the foundation on what the comparison is to be made between - I was also intrigued as to the basis on your thoughts that it would handle well - It sounds like you were just being polite, which is fair enough.

[horrido]

Mar 12, 2021 21:02:37 GMT Darkspeed said:

Mar 12, 2021 20:25:26 GMT horrido said:

Hey relax, I´m just asking a question. Mainly as I don´t see anything obvious about it and I thought you might have an insight. 
Guess not.

I am horizontally relaxed - I thought my reply perfectly straight forward and without any emotion you seem to imply exists. I was just trying to establish the foundation on what the comparison is to be made between - I was also intrigued as to the basis on your thoughts that it would handle well - It sounds like you were just being polite, which is fair enough.

Ok, I was just thinking along the lines that there have been rear engined cars that handle well (and poorly also) and 2CVs also can be made to handle well. Also as I tend to favour RWD as a concept - and also since the motor is so light - would it really make much odds if it was mid or rear mounted? I´m genuinely curious. Every day´s a  school day and all that.

[glenanderson]

I think that while mid mounting would potentially offer the best weight distribution, if the physical/technical difficulties of doing so with the Citroen parts are either physically impossible, or just too great to sensibly overcome, then there’s no real advantage to be gained by putting the engine at the back. Having it at the front means being able to use the standard front brake and steering setup, puts the air cooled engine out in the fresh air, and maybe allows enough of the original chassis and drivetrain to retain the 2CV identity and escape the whole IVA bucket of nastiness.

Granted, it’s a big deviation from the brief, and some might feel that it’s the “easy way out”, but I’d have thought it would be worth considering at least.

[cb11acd]

To answer some of the above:

I am doing my PhD at Loughborough in autonomous vehicle ergonomics.

The engine is staying behind the occupant. That isn't negotiable. Putting the engine in the front will ruin the aesthetic, and that is something that I am keen to keep hold of.

This car isn't going to be on a track, hill climb or sprint. It will be driven on B roads. Handling is a factor to consider but in no way a driving principle in this project. The 2CV was never designed for track use but with some work can be made to handle quite well.

I have one aim for this, and that is to put a smile on my face when I drive it and nothing more. Some people find joy in driving cars on the limits of adhesion, others like to pose in show cars. I just want this to be fun, it is not a serious car.

To get this fun it needs to actually get finished. And to finish it I need to keep things simple. I am not going to design an IRS, the chassis for the most part has been designed and on the way to being built.

As for twin engined this has crossed my mind, but as a mild hybrid rather than another IC engine. Packaging a small electric motor, control electrics and a small battery or super capacitors would be straight forward, however getting it to live in harmony with an IC engine and controlling it properly would be an issue. If I do it I will do it towards the end.

As I am changing the engine and chassis I am beyond having enough points to avoid IVA, so it's getting IVAd.

Hope that clears things up.

[glenanderson]

Cool.

Like a simple cycle-car style special. There’s a lot of merit in minimalism.*








* and as you’re starting from the benchmark of a 2CV and taking stuff away, minimal is definitely what you’re going to get. 😃👍

[sonus]

I like your solution!

It reminds me of my engine build. Most people just shake their heads and tells me to get a Ford 289 V8 to make Griffith clone, but what’s the fun in that. Instead I am taking the difficult and seldom throdden path of building a 2.8 litre Daimler Hemi V8 with fuel injection. I could probably had twice the power at half the price with a Ford 289, but I do not want a bolt together engine. I want to know I solved the problem with Ford Y-block lifters, bespoke camshaft, bespoke cast and machined pistons, custom and puls tuned intake and exhaust, adapted Ford ATI crankshaft damper, bespoke 5-speed gearbox conversion and lots more. And all of this because it is challenging and fun and It will be me who has made it just like I want it👍

So I say stick to your plan and I am looking very much forward to following your progress

[legend]

it all reminds me of a design project we had when i was a student and we had to create a K class sports car. Lots of students went for 2CV running gear and being aircooled super compact etc it's easier than sorting out radiators etc.

Could the rear arms be spaced out wider to miss the heads?

[cb11acd]

Mar 13, 2021 15:04:42 GMT legend said:

Could the rear arms be spaced out wider to miss the heads?

I could, the rear track will end up quite wide though. I think given the work to widen the rear axle raising it up a bit would be preferable.

When I get access to CAD again, I am going to do a more detailed model and see how the CoG changes in the rear Vs mid engine layouts. Rear engine simplifies so much I think it's worth considering but I want to ensure I won't end up with a 70-30 weight distribution or something silly.

I think the two options are a low but rear engine layout, or a high but mid engine layout. But without modelling both I won't know if this is a big difference or a negligible difference.

For now I can carry on with pedel mounts, steering column design, seat position etc.