Group C replica Mazda 787B

[RobBiggs]

Hi guys,

For anyone that is interested, I am putting my mechanical engineering degree to good use and am building my own car from scratch. I've decided on the Mazda 787B to model the bodywork on but all working parts such as chassis, wishbones, uprights, steering etc.. will be of my own design and more suitable for what will hopefully become a road legal car!

After many months of design work the build is now underway. The chassis is very near completion. I will be starting on the front suspension components soon. I will upload some photos of my work when i next get out to my shed with a camera.

I am posting on here for any thoughts/suggestions. My ultimate goal with this project is to produce a car that i may sell to potential customers and my biggest issue at the moment is how far to go with making what is essentially a road going racer, user friendly for the public roads. Are people really bothered about aluminium panel clad interiors, minimal bucket seats, firm suspension etc?

Many thanks,

Rob

[ajprice]

Nice idea, and good luck with it!

The first thought with making a Group C racer road legal (to me, anyway) would be speed bumps and rougher road surfaces. Does your suspension have any height adjustment?

[Sam_68]

If you're intending a marketable, road legal car then I'd second what ajprice says: ground clearance is going to be your big issue.

And even if you provide suspension lifters to get over the speed bumps, if you run with stiff enough suspension to achieve an 'authentic' Group C car look (check out the distance between the top of the wheel and the top of the arch in aj's photo), the thing will be uncontrollable on the lousy tarmac of British roads, skipping about from rut to pothole to manhole cover, unable to grip or put the power down.

You are going to have to compromise on that front, and since Ultima has been there before you (with many years of development) you could do worse than researching the sorts of clearances and suspension rates that they are running for road use as a starting point.

[singlecoil]

RobBiggs said:

Are people really bothered about aluminium panel clad interiors, minimal bucket seats, firm suspension etc?

Sounds quite luxurious for the average kit car.

[RobBiggs]

Yes ground clearance is an issue that has been with me throughout the design process. I have read almost every book and every piece of literature i can find on suspension design. I have worked through from the basics of ride frequency and bump/rebound travel and have arrived at wheel rates not too dissimilar from those on an ultima. I know i guy with an ultima and he has been a great help in indicating what works and what doesn't!

I designed the suspension geometry with variable ride height in mind, enabling a slight lift to clear large speed bumps and a drop down to even lower ground clearances for track use.

[Furyblade_Lee]

Call me lazy, Id just re-body an Ultima Chassis in a Mazda-like group C silhouette. But then I am not as clever as Lee Noble!

[odyssey2200]

This is gonna be good.

We need pictures ASAP

[kennyrayandersen]

Also, you might look at the Porsche 962. I'm not sure which group it is since I don't follow racing THAT closely; but, it was a sexy, sexy car, very successful (I thought), and there was a stunning road-going version (I wish I had one in my 'stable').

http://en.wikipedia.org/wiki/Porsche_962#Road_vers...

The original chassis, a believe was aluminum and wasn’t as stiff as some folks wanted, but there were several making modifications and even their own chassis. Anyway, the point being they did manage to get a extraordinary road version of a not too dissimilar car as you are thinking and it might be worth searching for a few pics.

[chuntington101]

You will want to have a look into the Ultima GTR. I'd say its the best road leagal Group C inspired car.

also might be worth looking into these guys 917 replica... might give you some ideas....

http://race-car-replicas.com/rcr917.html

Photos

http://race-car-replicas.com/rcr917_photo_album.ht...

Keep us posted on how it gose. By the way what engine are you planning on running????

[Paul Drawmer]

Minimum headlamp height for IVA will be a challenge.

[Sam_68]

Paul Drawmer said:

Minimum headlamp height for IVA will be a challenge.

...but it's quite easy to cheat on that particular test, unless they've tightened up the rules on blatant piss-taking recently.

[singlecoil]

Sam_68 said:

Paul Drawmer said:

Minimum headlamp height for IVA will be a challenge.

...but it's quite easy to cheat on that particular test, unless they've tightened up the rules on blatant piss-taking recently.

But there is no way that the headlamp mounting can stay the same as on the Mazda, that area is going to have to be redone. Probably won't matter though, unless people looking at it have a good memory, or it's parked next to a real one.

Edited by singlecoil on Thursday 31st December 10:09

[pilbeam_mp62]

singlecoil said:

RobBiggs said:

Are people really bothered about aluminium panel clad interiors, minimal bucket seats, firm suspension etc?

Sounds quite luxurious for the average kit car.

Well - you either try to compete with the Ultima, in which case you will need an interior that is fairly presentable :-



or - you go down the other end of the spectrum, and compete with this type of car :-

http://www.kellforms.com/retoga/sales.htm

(Although this one would need work to make it road-legal, I guess)

Best of luck with it - Maybe you should get together with singlecoil - he is doing something like this, I think ?

Regards

[Sam_68]

singlecoil said:

But there is no way that the headlamp mounting can stay the same as on the Mazda, that area is going to have to be redone.

Not necessarily - all you have to do is make up a couple of 'frogeye' pods for the test that mount where the perspex covers will later fit. This is the approach used by Westfield, for the Eleven.

[singlecoil]

Sam_68 said:

singlecoil said:

But there is no way that the headlamp mounting can stay the same as on the Mazda, that area is going to have to be redone.

Not necessarily - all you have to do is make up a couple of 'frogeye' pods for the test that mount where the perspex covers will later fit. This is the approach used by Westfield, for the Eleven.

They would need to stick up quite a long way though, but I guess that could be done (500mm to bottom of headlight BTW)

Just need to hope you don't get pulled by BIB that knows the Construction and Use regulations, alos might be a problem at MOT time, will the beam tester get that low?

[Sam_68]

singlecoil said:

Just need to hope you don't get pulled by BIB that knows the Construction and Use regulations

Happily, I've never come across a BIB who what that much of an ahole - the ones who are into cars sufficiently to know C&U to this level of detail (and I've been pulled by one or two over the years) tend to be pretty tolerant of minor transgressions like this and you tend to get the 'knowing cameraderie' type of comments instead of a ticket.

I must admit, though, I was surprised at the level of piss-taking suggested for the Eleven, given that it comes from a 'major' manufacturer like Westfield. IIRC, apart from the 'frogeye' headlamp pods, they recommend that it is put through the test minus doors and windscreen (both non-compliant) and with 'temporary' wing mirrors and steering wheel. And, of course, if you choose to use wire wheels you'll need to either fit them later or find compliant hexagon hub-nuts instead of knock-on spinners.

[Funky Diver]

RobBiggs said:

Are people really bothered about aluminium panel clad interiors, minimal bucket seats, firm suspension etc?

Hi Rob,

Take a look at the stirling work that MEV has done, and why does the Ariel Atom do so well? BUT, if it aint got poke, it's just another bath tub on wheels... so yes, they aren't bothered so long as there's a USP (Unique Selling Point) that attracts folks.

If you're looking at it as an all-in-kit-car-porfessionally-built-package-which-is-basically-a-factory-produced-car (sure there must be a term for that?) then you need to make sure that your quality AND aftersales is absolutely spot on! How is the car serviced and by whom? All these home made parts... what about spares? The big plus for kit cars currently... they use road going car parts. Make too many unique parts and your business model (do you have one?) becomes obsolete.

Other than that... let's see it

[brynd4321]

You’ve picked the wrong Mazda for the “wow” factor. Have a go at the Furai. That will sort out the head light height problem.

http://www.youtube.com/watch?v=C4Xl0i4uNGU

[RobBiggs]

Here's a pic of the spaceframe off the jig and on the floor yesterday



Thanks for all your help guys, i really appreciate it. I have been employed as a mechanical design engineer for the last 3 years and i now have a fair bit of experience with project design, managemenet, aftersales etc so this will hopefully put me in a good position for this project. As i said i'm really on here to show everyone who's intersted what im up to and to make sure im producing a car that is what people want. As many of you have pointed, the Ultima GTR is probably the best Group C inspired car out there at the moment and is probably the biggest factor in inspiring me to take on this project. Aside from all the research i have done on the group C / GTP cars, i have also spent a great deal of time looking at the ultima for how certain aspects of a race car must be adapted to produce a legal road car. As such, although my car will be modelled visually on the Mazda, obviously there will need to be some tweaking in order to meet rules and regs etc.

I think compared to some kit cars, more of the individual components will be bespoke but i wanted it to be this way so that aspects such the suspension geometry can be exactly as i want them to be. Where i work we design and manufacture low-volume bespoke vehicles, fabricating and machining almost all components. Aside from the manual machine tools i have in my own shed, at work i do have accesss to full cnc machining and turning centres. So although parts may for this first prototype be one-off specials, i will still have the designs and machine programs to produce more sets of parts/spares if i need them.

For those of you with a keen eye, the engine i will be using in this development 'mule' is a 4.2L N/A Audi V8. It is running around 360hp in this current state of tune and i am sure will be ample enough for testing. I picked up the engine fairly cheap along with the transaxle, so i can really test the car when its up and running without worrying to much if either of the two lets go ! The only downside to the audi transaxle is that it is incredibly short from mounting face to output CV joints. To keep the engine forward and maintain weight distribution i will be fitting a bell housing between the transaxle and engine.

I have uploaded more pics at: http://groupcreplica.blogspot.com/

As a side note, the other car i considered modelling my car on is the Nissan GTP ZX-Turbo. I decided against it because of the love or hate it appearance. I personally think it looks ace but i'm sure its not to everyones taste!

Edited by RobBiggs on Friday 1st January 17:53

[pilbeam_mp62]

Very impressive Rob - you are making a lot of progress - I will follow this project with interest.

One question - and I am certainly no expert - can you comment on the sharp angle between the steering rack itself and the steering arms (shown in your first CAD picture)

I would have thought that this type of geometry could cause some problems with bump steer ?

Regards