Looking for help/advice with build

[petawawarace]

I picked up a used Pro Formula Mazda. It basically has nothing behind the tub other than the old RX8 engine mount. I plan on putting a bike engine in it (2005 ZX-10R) and building the back-half of the car. I know that the carbon tubs are not allowed in F1000, but the rear section would be identical to the F1000 stuff. I'm hoping to do this real LOWBUCK, but I've got a decent little fab shop here at home. Ive seen lots of great builds on here, and I'm wondering if I could get some help and advice while doing this?? I have lots of experience with oval racing, and building those cars, but not so much with the road racing side of things. I've added a list of things I'm hoping some of you guys can answer.

Rear suspension: Since I'm building this all from scratch, I'd like to use parts that are easy to find and relatively cheap. I can build my own wishbones, pick-up points etc, but things like the axles, uprights, diff etc I'm not sure on. I know I could custom make everything from scratch, but if there are pre-existing parts out there, it would obviously make life easier. I literally have nothing related to the rear suspension, so I've got a clean slate.

Diff: I know I can buy a Quaiffe etc, but I've seen guys use LSDs out of road cars and modify them for chain drive. Anyone have insight or done this? I like this as its a very lowcost solution. Or can I go with a locked rearend? If so I would like to have the option to convert to a LSD down the road. I could make my own center shaft and make it the same size as a Quaife or similar so I can convert easily later on.

Rear Brakes: I really like the idea of a single rear rotor/caliper. Obviously it would need to be larger than 2 outboard ones, but how does this work with an LSD? Will it work? Depends on the type of LSD?

Parts: Other than the classifieds here and I've already found Pegasus, is there a good source for odds and ends? preferably used parts???

Thanks for the help guys...I'm sure I'll have more questions as I go.

Jeff

[ghickman]

This sounds like a pretty cool build. I would build it to modern formula car specs. This way you have a car that could potentially be an Atlantic killer and also have some resale value.

I have complete uprights in stock that can be used with either a CV or Tripod drive. I can share enough CAD data with you for the uprights which would speed up your build process.

OPEN DIFF VS LSD VS LOCKED:
In my opinion if you are going to build a car that is fun to drive then your only choice would be LSD.

My second choice would be an open diff, which I have tested before with decent results.

Locked diff would not be an option in my opinion. You'd most likely have understeer up the wazoo.

BRAKES:
I would only recommend a caliper at each wheel. Why compromise the peformance and cheap out. Calipers such as Wilwood are priced right and work very well. You can make your own rotors or buy them at very resonable prices.

[glenn cooper]

Sent u a pm

[Rick Kean]

A Hewland LD200 sized diff may make the most DIY sense.

David Palatov did a 4WchainD 2caliper track car, but the front brake failed to behave. His blog is an entertaining read. The 10/08/06 entry discusses a front brake test spin.

Rick

[glenn cooper]

I'd go bigger than 1000cc - There's be no reason to go w a 1L, unless you had an engine/ oil system/header already and were just set on that.

The car will weigh considerably more than a F1000, I'm thinking, so go w/ the more reliable, lower reving, max torque at a few thousand less rpm 1340 Hayabusa.

DO NOT go w/ a spool or locked differential. There's about 3 people in the country who drive that get up well enough to represent, and hundreds who tried it and said "Yeahhhh, not so much"...

I'm not a fan of Wilwood stuff - I guess I'll never get past the fact that a pad set costs more than a caliper (!)

Mike Devins of Hurley Racing Products / HRP has done a modified automotive dif as you described. Taylor or WRD both have great great driveline.

I have a damaged rear frame half from an RFR F1000 which at a minimum can be used as a guide, and/or repaired.
I also sell complete low hour, no excuses engines and have a 1340 cc Hayabusa carkit w/ just a few thousand miles on it.

Regards, GC

[petawawarace]

Thanks guys. Glenn, why do you think the car will be heavier than an F1000? Just curious as I thought I would be right around 800lbs. And while I agree a bigger engine would be great, I do already have an 05 Zx10r (looking for dry sump kit) and this is going to be my first formula car and feel a 1L will be fine for now.

The only reason I'd consider a locked diff is because we are running one now in a legends car with an R1 and its behaving great. That said do you guys think a locked diff is scrubbing too much speed and costing time?

[Jnovak]

You will really love the big Hayabusa in the car. Much more torque and power with MUCH better reliability.

[glenn cooper]

On the weight thing I was just doing some in my head calculatin', which can be dangerous at times...

Your numbers show:

Pro FM
- Rotary and transaxle
= X
and
X + ZX10R and dif = 800?

[Dwayne Anderson]

Glen I have a Pro FM up right you can have if it will work Dwayne

[petawawarace]

I will take an upright if you have it. PM me for details.
Thanks, Jeff

[DWickman]

Where in Canada are you?

Desmond
Calgary

[petawawarace]

About 2 hrs west of Ottawa, but the car came from the Calgary area.

[Brian]

I spent a lot of time in Petawawa blowing things up in my youth... Artillery range, making small pieces of junk out of large pieces of junk, from 7 miles away...

Get to know David Clubine at Britain West, they build a lot of A-arms, uprights, brake pieces and other bits that can help you out. They are in Brantford just west of Toronto. I would first try to duplicate the original rear suspension geometry of the Mazda, failing that design to use commonly available uprights and components for something like a late model Van Diemen, for easy availability of parts.

Brian

[petawawarace]

I've been here my whole life. Not military, but dad works for the base.

Could anyone get a measurement on some of their diffs for me? I want to know how wide they are from flange to flange. Just trying to get the design of this thing started before I spend all the money on parts. Thanks, Jeff

[Rick Kean]

Hell's bells oh well.

http://www.hewland.com/svga/down%20loads.htm

For instance, the LD200 Installation Dwg's show Driveshaft flanges drawn at 2x4.700in, or 9.4 inch apart, outside-to-outside.

Rick

[S Lathrop]

Years ago I build a rear drive assembly for a DSR. I used the differential, side plates and the output flanges from a Hewland Mk9.

I built a box that was open to the front for the chain. The side plates from the Hewland bolted to the sides of the box. When assembled, the assembly bolted to the frame just as Hewland MK 9 would. The box duplicated the center section of the VW transaxle.

There is no reason that you could not do the same thing with all VW parts from an IRS, air cooled Beatle. You just replace the ring gear with a chain sprocket and build the box big enough to clear the sprocket.

You might be able to find a Staffs gear box and do the same thing. There are several limited slip diffs available for the Staffs gear box. Many of those options are also available for the old Hewland MK 9 as well.

This approach would allow you to get something that would be very inexpensive to start with and allow you a lot of options for upgrades.

[sccadsr31]

If you are going to run the ZX10R wet sump check out my post on oil puking problems
http://dsrforum.yuku.com/topic/10175/ZX10R-oil-puking

David

[Frazer Mackay]

I can recommend a guy in Scotland that specialises in chain drive differential conversions. I believe he already does some work in the US for the Formula SAE fraternity. A much cheaper alternative to Quaife or equivalent if you are looking to save cash. He also does single diff mounted brake discs you are discussing. He's a good guy and it's made to order so you can get exactly what you need.

http://www.westgarage.co.uk/forsale/kits/pivot.html

Just on the single in board discs. From a pure design perspective they do look good but I can't bring myself to go that route. We've all heard, seen and had drive shaft failures or CV failures. It happens. Normally under drive it just ruins your race or at worst your whole weekend. If it happens under braking, arguably way more torque, then ................. oh dear. Jochen Rindt was the victim of an inboard brake drive shaft failure.

The other thing I have never liked about them is when you think about what happens under braking if you lift a wheel over a bump or otherwise??? In theory you end up with zero braking on the rear axle. If the LSD is preloaded then you'll at least have the preload torque but that's it. The counter argument is will a formula car, low to the ground, on tarmac lift a rear wheel?? You see enough of them around so I guess I am just wrong and it does work. Doesn't sit well with me though.

Is cooling an issue with the brakes inboard?

Legends are great fun little cars to drive and the solid axle really makes them fun. Unfortunately if you drive a formula car in the same way I don't think you'll see many podiums. Also your new car is likely to be considerably longer than a legend meaning the handling characteristics are unlikely to transfer. I agree with the predicted turn in understeer. LSD would be my suggestion. Most LSD's allow for quite a bit of playing with so you can tune it's characteristics on and off throttle.

For some inspiration on rear end design check this out. My favourite motorcycle engined car in the world to date. AWESOME!! It doesn't get much smaller than that. Less the rear wing support space frame there isn't much too it. Worth a youtube visit too.

http://www.lee-adams.co.uk/lee_adams_gallery_1.html

[S Lathrop]

Rear Brakes: I really like the idea of a single rear rotor/caliper. Obviously it would need to be larger than 2 outboard ones, but how does this work with an LSD? Will it work? Depends on the type of LSD?

Don't even think about using a single or even 2 inboard brakes on your car.

I have built and raced cars with inboard brakes. Very quickly I changed anythnig I drove to outboard brakes, even though I sold cars with inboard brakes. Heat and contamination of the disks from the engine are issue that you never adequately solve. Finally your chain drive diff assembly will have enough issues with drive torque. There is no reason to add brake torque to that assembly when the suspension is already dealing with the braking forces.

[petawawarace]

Thanks guys, I think ill be going with the traditional outboard setup. Looking at making my own lsd drive setup too. I had found the guy from Scotland earlier and got some great ideas there.
Been gathering parts and hoping to make some progress once the snow starts flying

[ayseven]

You going to have this thing ready for next season Jeff????? Can't wait to see it!

Rich
VanDiemen Sports 2000
#155

ps.. my car is for sale, although I have not advertised it yet. Going Formula single seater... if you find anybody interested let me know through Nigel

[petawawarace]

Rich,

At the rate I'm working on it now, it might be ready in 4 or 5 years. I've been buying parts lately, but not much work. I'm hoping to get a lot done this winter though. Late next year for a shakedown test is a goal I've set, but we'll see.

[ayseven]

Well, I know how long these things take! And of course they are never actually finished. Drivable though if all goes well. Too bad I am in Aylmer, a million miles away from you.