Scratch built racecars?

[sperry]

Originally Posted by rory_a

Thanks for the info - regarding my interest/concern in classing - I was building a Formula Vee car, and started work based on SCCA specs, so I was uber concerned with class regs. I gave that up when I realized I couldn't bring myself to dump $5k into building up a 40hp engine, and building a ball joint beam, 1600 car would be no better.


My intentions are to run Novice as long as possible, and run what I have (RE070s on 7.5) until they're shot.

I wanted to build a FV. Until I started looking around at buying a used one to learn in and realized just how used a 40 y/o race car actually is. Blech.

If only Formula Mazda cars weren't $100,000+!

[rory_a]

Australia has Formula First - ball joint beams, 1600 dual port engines, lots of potential - they have hp regs but they're mainly detuned 120hp $15k+ stockish OE VW dual port 1600 engines. That's where I was going. Unfortunately, I'd be up against all the other open wheel cars as it wouldn't officially fit in Formula Vee, or any low-displacement open wheel class.


(the thought of dropping in a turbo 2332 was passed around though 400hp in a 800 pound car FTMFW!!!!)

[sperry]

Yeah, the FF cars look like a blast. Unfortunately there's just no real racing to be had for them in the States. Really, the best way to go is probably Spec Racer Ford. It's not open wheel, but it's close, and they pull 40+ car fields at even lightly attended races.

[rory_a]

Honestly, I'd rather buy/build a track ready drivable STi


Not gonna happen in this lifetime though, at least with my chosen career.

[sperry]

Originally Posted by rory_a

Honestly, I'd rather buy/build a track ready drivable STi


Not gonna happen in this lifetime though, at least with my chosen career.

I dunno... I've got basically that in my WRX. I think an open wheel racecar with 1/4 the horsepower and 1/4 the weight is going to be twice as much fun as a race built STi; slower on the straights for sure, but *much* faster in the turns. It'll also be a crapload cheaper to race. My WRX at the peak of my time trials racing cost about $1000/hour to operate considering the cost of 100oct fuel, r-comp tires, and touring car compound brake pads.

[zpeed]

What about gokart? too small?

[sperry]

Originally Posted by zpeed

What about gokart? too small?

I've considered it... But at 6'4", a kart is probably a little too small. Plus, I'm not up for getting beat up in a wreck like a motocross racer.

[rory_a]

I've considered picking up a wrecked Hyabusa, solid axle quad rear end, and building a chassis to hold it all with double a-arm front suspension. Not sure what off-the-shelf parts would be out there for brakes though.



And, Caterhams are always a decent alternative

[rory_a]

Figure for $25K you could have a built VW transmission, turbo VW engine, fab up some a-arms, Wilwood brake parts (front, VW Wilwood brake set rear), Erco VW wheels (7lbs/each), and a chromoly Formula Vee style chassis. Wrap it in fiberglass. 400 hp out of a built, turbo'd VW engine isn't that difficult anymore. But reliability would be lacking.

Or, pick up a Kennedy Subaru/VW bellhousing adapter and clutch set up and throw in an STI mill, deal with water cooling, and you have a reliable track car.















I've put absolutely no thought into any of this

[AtomicLabMonkey]

Originally Posted by rory_a

I've considered picking up a wrecked Hyabusa, solid axle quad rear end, and building a chassis to hold it all with double a-arm front suspension. Not sure what off-the-shelf parts would be out there for brakes though.

I've been working up a similar formula car idea in CAD lately just as a design exercise. I have it mocked up with a Hayabusa engine currently. I attached the page on it from my engineering portfolio; it's changed somewhat since these screencaps but the concept is there. Current weight without ballast is ~700lbs, ~40% front bias. There are more components to get in the model though and I still need to run all kinds of FEA to optimize things. As it sits now it would be classed as an A-Mod car for auto-x. Not sure about road racing.

Packaging everything is the hardest part, especially at the wheel/upright. If you're trying to use existing parts such as wheel bearings & brake rotors/hats/calipers, it's difficult to fit everything together while maintaining the geometry and dynamic response you want from the suspension.

There are lots of brake vendors out there to use; Wilwood and AP Racing are the catalogs I've been looking at. I have no idea why you would want to use a stick axle, though. Just a bad idea all around.

[sperry]

Hey, that's pretty bad ass! All Miata running gear?

I've been thinking that a Formula-Vee or Spec Racer Ford type car with an EJ series N/A Subaru motor w/ FWD gearbox in an MR layout would be a fun entry level type racer... wanna draw that up next?

[AtomicLabMonkey]

The wheel-side stuff like bearing, hub, cv, are Miata parts, at least for now. It was a simple way to have a starting point to build around.

I thought about going all out and doing a F1000 design, but I couldn't find a good 1000cc engine model out there and I doubt my computer right now has the juice to model all the bodywork/wings and run CFD anyway. All the parts models would adapt to a different rules set & engine pretty easily though, so maybe down the road sometime.

[rory_a]

Originally Posted by AtomicLabMonkey

There are lots of brake vendors out there to use; Wilwood and AP Racing are the catalogs I've been looking at. I have no idea why you would want to use a stick axle, though. Just a bad idea all around.

That is very bad ass.


My only reasoning for using a stick axle was ease of build. Considering my tools consist of standard hand tools, grinder, and 110 mig flux-core welder; and budget is next to nil, drafting up a complex design and whatnot is/has been out of the equation. Also, never thought of adapting Miata pieces, as my knowledge of the cars is also next to nil, other than thinking one would be a fun "little" build project.


Honestly though, I'd be much more inclined off the bat to build a Formula Vee - based car as that's what I know. Thinking swing axle tranny (yeah, I know.....) with z-bar style single rear coilover suspension, heavily modified ball-joint front beam based suspension using a torsion spring stack and a through rod to allow for coils - the torsion and through rod would act as adjustable sway bars (as they were used in vintage FV). This way I could at least get the suspension together and have the roller with a simple chassis. Only way to keep the weight down would be Chromoly tubing, which would necessitate a TIG. I'd likely have access to a chromo-compatible TIG (at Trent Fabrications) as well as tubing benders, cut offs, notching set-up, etc.

So the chassis would be a "fairly simple" endeavor. For my own ease, I'd run all VW-based parts and a VW drivetrain as that's what I know. Having a car weight of 800 would depend on tubing specs - VW tranny weight, rotor to rotor is under 100lbs, fully assembled turbo-spec'd engine roughly 250, front suspension under 100lbs, 9lb wheels.....


Still, wrecked Hyabusas and other sport bikes are all over the place, and to be able to set the car up with a reliable-as-hell, light-as-hell engine and tranny set up would be the shit.

[AtomicLabMonkey]

I only thought of using Miata stuff because I happen to have a Miata sitting in the garage to take apart and look at. It lined up nicely with the target size & weight of the design. Miatas use a 4x100 bolt circle wheel/hub, and there are lots of options out there for compatible wheels in sizes I wanted (has to be at least 13" to clear any decent outboard brake setup).

Beam and swing axles are just horrendous. I know, you work with what you've got, but damn they're bad.

4130 is great for suspension links if you're going to properly heat treat it after fabrication. Otherwise, it's not that much stronger than mild steel. This is also why I would not make a frame/cage out of chromoly. Unless you have some cash you're not going to post-fab heat treat an entire chassis, so it's much simpler/cheaper to build it out of mild.

My frame right now is ~80lbs assuming 1020 steel, with some brackets and a few extra tubes to be added in here and there once I do some stiffness testing. So it'll probably end up about 100lbs.

[rory_a]

Originally Posted by AtomicLabMonkey

My frame right now is ~80lbs assuming 1020 steel, with some brackets and a few extra tubes to be added in here and there once I do some stiffness testing. So it'll probably end up about 100lbs.

Wow. Damn good work there in weight and chassis optimization! I guess it pays to have proper equipment and tools when planning.


I know swingaxles and torsion beams are the devils work. No argument there. Wouldn't be much work to utilize a VW IRS trannsaxle over a Swing. Build a 091 bus box and you have a 4-speed version of an early 911 box. Using a big turbo engine, the right R&P and gear ratios should net decent gearing for auto-x, but have no top end for track. Main difference between the IRS and swing would be running triangulated trailing arms, not a big deal.

My dad ended up with a 13-link rear end on his '66 Vette's new chassis (IRS - 4-link, camber links, triangulating links) - my IRS configuration should be much simpler (4-link, triangulating links, z-bar links).


My understanding was that 4130 was stronger than steel (with never hearing of heat treating it either), therefore you can run a thinner tube wall and tube, netting a much lighter chassis. At least that's the way they sell it for VW drag chassis - at more than twice the cost.


I wish I had a Miata laying around to mock up parts - I would simply build it instead

[AtomicLabMonkey]

Originally Posted by rory_a

My understanding was that 4130 was stronger than steel (with never hearing of heat treating it either), therefore you can run a thinner tube wall and tube, netting a much lighter chassis. At least that's the way they sell it for VW drag chassis - at more than twice the cost.

Well, they're both steel. 1018 or 1020 for example are regular mild carbon steels, and 4130 is a higher carbon content steel with chromium, molybdenum, and some other good stuff mixed into the metal composition. BUT.. 4130's strength is all about how it's been heat treated (quenched/tempered).

If you compare their yield strengths in the normalized condition, 1020 is 50,000psi and 4130 is 63,300psi (data from my machine design book). Sure, it is a bit stronger, but in my opinion that fairly small percentage gain in strength is not worth the cost/hassle of dealing with it. If, however, you properly heat treat 4130, you can achieve a pretty fantastic yield strength like 150,000+psi. But to do this, you have to stick it in an oven, heat to something like 1600*F for a good while, take it out and immediately quench in water or oil bath, and then reheat to a few hundred degrees for a set length of time to relieve some stress and regain some ductility. The end product's mechanical properties are all about that voodoo magic that happens at the heat treatment shop.

So, yes, you can design lighter weight parts out of 4130 that will carry the same load as a 1020 part, but only by heat treating it. This is why smaller parts like control arms, welded uprights, shafts, etc. are very frequently made out of 4130, but very big parts will typically not be. Generally, the bigger the part, the more expensive it is to heat treat. The shop you use has to be able to physically fit it into their ovens & quench baths.

Also, parts can distort a bit during heat treatment as things heat/cool and the stresses in the metal are relieved, so for something like a frame where you have suspension mount points you want to keep in alignment across a long distance (like from opposite corners of the car), it could be hard to control the end result.

[rory_a]

I see what you did there Scott, clever






(that comment may in fact become confusing one day )

[rory_a]

Originally Posted by AtomicLabMonkey

Well, they're both steel. 1018 or 1020 for example are regular mild carbon steels, and 4130 is a higher carbon content steel with chromium, molybdenum, and some other good stuff mixed into the metal composition. BUT.. 4130's strength is all about how it's been heat treated (quenched/tempered).

.....

INCREDIBLY good to know for all who are looking at chromo cages, frames, chassis. I can all but guaranty none of the chassis or bars available to the VW community are treated to any heat aside from welding.

[rory_a]

I'm having evil thoughts right now, I think I'm gonna end up re-building my ragtop, just can't figure out where it's gonna be classed. I know I don't need to worry right now for AX classing as I'll be in newb all this season, but I won't have the car running until next year anyway. As it sits, I have modified suspension geometry with dropped spindles and a narrowed front beam. Trying to figure out where it'll be placed naturally, and what I can do to place it in a decent class where it'll still be competitive.

At this point, I'm figuring Modified is the only way to go - the car's supposed to have a 36hp 1100+cc engine, and there's no way I'd run less than a 2110. Between suspension geometry and the engine, I think I might end up wasting my time with it.

Thoughts?

[Kevin M]

I think you are okay in Prepared. Probably in FP. With me.

[rory_a]

Yeah, that's exactly where I want to be



I'm guessing you're talking about the RS? A built RS, with a Subie shop's backing? With years of experience making fast cars faster? Or, you're talking about the Forester, which would be even more, umm, even???

I'd so totally stand a chance on that one

Wait, I don't remember the year's rankings off hand, but I don't really think there was anyone running FP or HP (which the bug would likely be placed in as it's slow as hell stock) except maybe Cory, so I'd have a chance at third, right?

[Kevin M]

Is there an HP? If so, maybe you'd be there.

I'll be in FP next season in my '93 wagon with built motor and crazy drivetrain stuff. No turbo, but it will be crazy light.

[rory_a]

That's sounding interesting

Not sure on HP - and if you're '93 Wagon's going to be in FP, the bug would likely be as well. I may end up with a '03 Ford Focus auto-x beater, so that'd end up getting some work and likely end up in the "Ps".