Planning stage on my home built autocrosser ....

hhaase wrote: You'd mentioned adding ballast as diminishing returns.I don't understand that,build it light and add ballast where best suited to meet your target is a time proven effective method.

kevlarcorolla wrote:

Actually I'm not against using weight to tailor the car to where I want it, just that if I'm adding weight I'd rather use things that are useful as opposed to just slugs of lead. I'd prefer to add weight via a fire system, accu-sump, telemetry components, battery, things like that.

I agree 100% but I think you missed my point,I don't think you will hit your target weight with the layout/parts chosen.That means you either don't get the extras,you live with the lower performance from being underpowered or you spend money to make more power to get back to the target lb/hp.

The end result will be less performance,given a choice between two cars with identical power to weights I'll take the lightest one every single time.

I really do hate to be Debbie downer but your about to go down a very long road with a scratch built car,I did mine from start to 1st drive in 7 months but that was every weekend and 4 nights a week in the shop.Not many people are willing to put the effort in,even fewer are able to finish a project of such effort.

It would be a major bummer to have the end result not live up to expectations.

I get that you want to use an engine you have,between the internet and the big box truck you can have any engine you can dream up and afford delivered right to your door.

I don't see your cg being noticeably lower with a transverse or longitudinal layout,I'm confident transverse is much easier to manage and not compromise other parameters of the design.You haven't said what your front to rear bias target is,with the wheelbase and seating postion the longitudinal layout forces I'm guessing your looking at 50 to 55% rear bias?.

if going transverse is too tall, you could look at laying the motor over like Onyx Sports Cars did with the Mongoose. although, you'll probably have to use the wayback machine to find the pages they used to have on it.

kevlarcorolla wrote:

hhaase wrote: You'd mentioned adding ballast as diminishing returns.I don't understand that,build it light and add ballast where best suited to meet your target is a time proven effective method.

kevlarcorolla wrote:

Actually I'm not against using weight to tailor the car to where I want it, just that if I'm adding weight I'd rather use things that are useful as opposed to just slugs of lead. I'd prefer to add weight via a fire system, accu-sump, telemetry components, battery, things like that.

I agree 100% but I think you missed my point,I don't think you will hit your target weight with the layout/parts chosen.That means you either don't get the extras,you live with the lower performance from being underpowered or you spend money to make more power to get back to the target lb/hp. The end result will be less performance,given a choice between two cars with identical power to weights I'll take the lightest one every single time. I really do hate to be Debbie downer but your about to go down a very long road with a scratch built car,I did mine from start to 1st drive in 7 months but that was every weekend and 4 nights a week in the shop.Not many people are willing to put the effort in,even fewer are able to finish a project of such effort. It would be a major bummer to have the end result not live up to expectations. I get that you want to use an engine you have,between the internet and the big box truck you can have any engine you can dream up and afford delivered right to your door. I don't see your cg being noticeably lower with a transverse or longitudinal layout,I'm confident transverse is much easier to manage and not compromise other parameters of the design.You haven't said what your front to rear bias target is,with the wheelbase and seating postion the longitudinal layout forces I'm guessing your looking at 50 to 55% rear bias?.

Trying to get as close to 50/50 bias as I can, I know it's probably still going to be shifted rearward by some degree, so I'll take as much as I can get.

CG lowering all depends on how you build it. could probably get the same Cg from a transverse layout, but then it means a more complicated chassis layout to clear everything, and also a wider cross-section. Longitudinal I can run single piece main stringers from the steering box to the tail, alongside and parallel to the crankshaft / input shaft line, and just above the drive flanges. If it was a two-seat layout and a naturally wider cross-section to the whole car then yeah, transverse would probably be fine.

I'm not looking to compete at the national level here. I'm just trying to build the car that's stuck in my brain, and have some fun with the thing, without spending a fortune. Though if I had the money, I'd LOVE to get a Hewland transaxle instead of basic VW.

Numbers still haven't convinced me I can't hit the weight. Friendly wager time?

kevlarcorolla wrote: especially a cast block 4ag,honestly there's lots of better options then those.I say that having built my own supercharged 20v and turbo'd 16v 4ag's for my AE86.

4AGE owner here, I cannot recommend this engine any more. It's on the heavy side, not exactly modern by today's standards, and used parts are getting very, very hard to find (I was shopping online for used cranks a while ago, found 2 in the US and 1 in the UK, there were 2 local because so many people race 4AGE-powered cars by me, only 1 was good enough to drop in as-is, got it from a rally driver who now runs a Hasselgren/FA 4AGE). You can pretty much build one from aftermarket parts, but those parts are madly expensive. And on that topic, they're relatively expensive to get more power from.

I'd say you should consider a 1ZZ-FE or 2ZZ-GE in place of a 4AGE - although again, just about any car engine is going to make it very hard to hit your weight goals. Some of the few car engines that are close to the weight of bigger bike engines are the Suzuki G13 series. There's also a Saturn engine that's very light IIRC, L-something?

I have considered the 2ZZ specifically, and long-term may end up with one of them. Just that the extra output will bump me up a class higher than I'm comfortable with right now. It's part of the reason I am planning with the 4AG, to make that later swap easier. Here in the states it's still fairly easy to find complete 16v engines, and probably even easier to find 20v's these days via import houses.

If I ever get back to what I used to be able to swing for fun-money the 4AGE/VW combo WILL get swapped, probably for a 2ZZ and Hewland Mk9. Though at that point an Ecoboost will probably be much more affordable too. I do miss my NY paychecks, that's for sure.

-Hans

Found I am a bit limited in what transmissions I can use to run flipped backwards. Need to find either a 914 transmission, or a VW Bug with swing-axles and dual sideplates.

-Hans

I guess I need to have a better understanding of what you have in your melon.

In the beginning you said you didn't like the look FSAE or F600 cars(I used to have an F500)and since an F600 is basically the same shape and profile of damn near every open wheel car ever built I figure that's off the table.

I immediately picture a very cabin forward backwards locost type thingy.

Also in my head if your main frame rails are above the driveshaft flanges don't you have to either run pickup truck diameter tires or have very steeply angled control arms to get the oil pan off the ground?

kevlarcorolla wrote: I guess I need to have a better understanding of what you have in your melon. In the beginning you said you didn't like the look FSAE or F600 cars(I used to have an F500)and since an F600 is basically the same shape and profile of damn near every open wheel car ever built I figure that's off the table. I immediately picture a very cabin forward backwards locost type thingy. Also in my head if your main frame rails are above the driveshaft flanges don't you have to either run pickup truck diameter tires or have very steeply angled control arms to get the oil pan off the ground?

I originally was thinking of getting a Formula Vee, and modifying it for NASA autocross. But they have only about 40hp, and terrible suspension front and rear. Started thinking engine swaps, and suspension upgrades, and essentially it's the same amount of work to just start from scratch.

Tires I'm thinking as a base measurement of a tire with 23" diameter. When I sketched it out, oil pan will be 180mm off the ground.

So I'm picturing something along these lines ..... but with low profile fenders, and side pods for engine cooling.

Something like this?

MrJoshua wrote: Something like this?

Perhaps a bit more ..... on the ground? In all seriousness, I almost went that direction, as it would solve the whole 'open wheel' problem. But then I realized I just want an open wheel car, or at least as close to one as I can get if I need to fender it. As a secondary use, I'd like it to be able to run track days and NASA TT, though autocross would be the main focus.

What I'm trying to avoid is this kinda thing.... Little things like this one would just scare the hell outta me on a road course.

Sounds like you want a DSR/B-Mod car.

I suppose it bears repeating - do you like building or do you like driving? From what I've read here and elsewhere, just keeping one of these cars in operational condition is a damn-near full-time job.

One of the guys on this forum (I think it was nocones?) ran a very successful DSR car for a few years, although I believe it was with the SCCA.

Lastly, I still believe building a car strictly to NASA rules may be shooting yourself in the foot.

I get the feeling you're trying to build something sort of like a BAC Mono or Ariel Atom - at least visually. There's no getting away from the basic similarities to an FSAE car, even if it's a bit enlarged in comparison.

Anyway, I had an idea for your powertrain this morning. Have you considered an electric powertrain? They've been cleaning up in FSAE (although the sportbike engines run restrictors there), especially the AWD builds. For autocross speeds you'd do just fine without a gearbox. You could put the motor below or behind the diff, or even run a pair of motors in place of a diff, and then put the battery pack where your engine would've gone. If there's enough space in the nose you could have AWD at the cost of increased weight and complexity.

If you make your pack just big enough to get you through an event, you can still hit your weight goals. You could even undersize it and charge between runs from a multi-alternator support vehicle, but that comes with increased equipment costs.

Ian F wrote: Sounds like you want a DSR/B-Mod car. I suppose it bears repeating - do you like building or do you like driving? From what I've read here and elsewhere, just keeping one of these cars in operational condition is a damn-near full-time job. One of the guys on this forum (I think it was nocones?) ran a very successful DSR car for a few years, although I believe it was with the SCCA. Lastly, I still believe building a car strictly to NASA rules may be shooting yourself in the foot.

I really like the driving side, but have always been big on building. Hell, I maintain electronics manufacturing equipment for a living. So I'm really looking forward to building, and maintaining, a car like this.

For an a SCCA comparison, I'd say more C-Mod actually.

I'll probably use the c-mod rule set to a large degree for safety purposes. May even try to keep it legal there, but since I primarily run with a group that uses NASA rules, I gotta keep that at my main focus.

I've built a couple of sports racers from scratch so I'll give you my thoughts. First, it really helps to decide on what rule set you're going to follow. You mention SCCA C-mod. I think that is basically Formula Ford and S2000 - so a spec engine, spec wheel widths, etc. Not much room to do your own thing. If you're looking for safety - don't use the Solo rules. Use the SCCA GCR. That'll cover what you really need if you want to do time trials, hill climbs or race (in other words, anything beyond autocross). If you'll run with NASA, you should look at those rules - maybe build so that both are covered in terms of safety so you can run either group.

If this is not a street car, I would only be thinking about race tires and race ride heights. If it's a street car - I can't help at all. For a race-only sports racing / formula car, you should be thinking of a ride height in the range of 1.5 to 2.5 inches. If it's race-only, you'll probably be using slicks. Look at what sizes Hoosier offers. You'll probably be using 13" wheels because most slicks for a formula / sports racing car are 13" (because they're lighter).

Most of these cars have a weight bias to the rear - maybe 40/60 - and that seems to be fine so I wouldn't get too worried about the magical 50/50 split.

Finally, a comment on weight. I've been down this road and it is hard to get under 1000 lb even with a bike engine (engine + trans = 150 to 175 lb). The DSR guys trying to get to 900 lb had to go to super thin carbon bodies, titanium everything and so on to get there. I don't think you'll get an automotive based engine / trans in a car under 1000 lb. You can still have a fun car but it's hard to beat a 180 hp bike engine /trans that only weighs 175 lb.

Building your own is a ton of work but a lot of fun. Enjoy it.

Titan4 wrote: Building your own is a ton of work but a lot of fun. Enjoy it.

And that's one goal I ain't compromising on, and the main reason I'm doing this. Other than that, NASA TT1 class, and their CCR rules for safety. No street legal requirement. Mainly autocross, perhaps HPDE and TT if I'm comfortable in it enough. Goals haven't changed at all. Just hard to explain a NASA build to folks that are primarily SCCA.

-Hans

Had my copy of "Chassis Engineering" by Herb Adams show up today. Good book, definitely a lot of useful info in there, can see it very heavily focuses on oval track cars by the focus on left/right weight distribution, corner wedging, and solid rear axle suspensions. Not much at all discussing fore/aft during braking and acceleration, and only a cursory discussion for independent rears. Still going to be very useful. Has me re-thinking a couple design features and I wonder if I can work in rear-steer front spindles instead of front-steer. Though with heim joints I wonder if it'll really make a big difference.

Nice to see his section on building up a scale version first. Was always intending to do this anyway, due to limited CAD access and ability. For some reason I had been thinking of doing a 1/6 scale, but changed my mind to do 1/12 instead. So I need to get some 1/8" dowels tomorrow and start putting something together.

-Hans

Rear-steer vs. front-steer should be chosen based mainly on packaging. Any difference in handling between the two is vanishingly slight.

In reply to hhaase:

I agree with GameboyRMH about the front vs rear steer.

Also, for what you want to design, I would look into the books by Allan Staniforth. Any of his books really. Much closer to what you want to build than Herb Adams' book.

This is a great example of what I'm picturing. If I go full-bodied, to be honest, it's REALLY darn close. Would go a lot narrower though for open wheel/formula style body. Hell, it's even got a DeDeon rear suspension.

GRM / Craigslist classified ad

Though the exhaust is really goofy, cage wouldn't be legal, and I do question some portions of his geometry and design.

Still ... looks like his wheelbase and width are pretty close to what I had calculated. Enough similarity that I saved the photos.

after looking at the photos of that frame... something to think about for autoX vs. hpde, is that you might want to have some kind of removable side-impact structure for when doing hpde... which might not be required on an autoX frame?

I'd also be a little concerned (even with a proper firewall) about the engine coming forward into the driver enclosure if you're run-over from behind (as if!).

you might look around youtube for some "rgb" footage from the annual Birkett race that the british 750 Moto Club holds annually. Would give a good idea of mixing it up on track in a single seater with full-size tin-cans.

This was advertised for sale here a while back.

LOLA T644E Formula Ford with GSXR-1000 conversion to F1000, FS, FB or Solo.

https://grassrootsmotorsports.com/forum/open-classifieds/mine-also-lola-t644e-formula-ford-with-gsxr-1000-c/106676/page1/

Pics are gone now tho.

Sounded like a helluva car, very tempting to a lot of us.

You couldn't build it for $7K.

The more I dive into planning on this one, the more I'm questioning a few things.

I've decided to shelve it for now and when the time comes to add another to the fleet I'll be looking at something already built and in need of a refresh. Too many good deals showing up this time of year on Formula Vee's, Formula Ford's, and all sorts of other cars within the style I want.