LocostUSA.com

quick update from the last month or so. just finished up some details on the front end, still lots to do thought. ive been mainly focused on the rear subframe, which i started last time home. done lots of drawing work on delta cad and trying to optimise the packaging while keeping the weight down. anyways any thoughts, concerns, suggestions welcome.

continued. well back at work untill late july. hopefully my springs, shocks and rod ends will be delivered from racetech by the time im home next. next order of business is hanging the diff, fabbing the a-arms, and fabbing coilover mounts.

Looks great! Thanks for the drawings btw. One more thing, what diff is that?

thanks.

the diff is out of an 82 toyota cressida. the stub axles have a 4x110 bolt pattern, the same as 94(only year for that size) miata driveshafts, although the centering bore on the stub axles is about .020 too small, so ill have to get that bore out slightly, still cheaper than getting custom drive shafts made. the 94 axle are about .75 inches shorther than the 90-93 axle, which i have a set of as well, so if i run into lenght issues, i can swap out axles to gain .75 inches or so.

i believe the diff is the same as the mk2 supra. gears are 4.1:1 for the standard cars and 3.9 for the autobox cars. im sure ill be looking to get the taller gears once i start driving it.

Andrew

Why did you decide on using a true automotive differential housing and rotate the bike engine, instead of running a chain to just the diff alone, like FSAE cars do? Just curious.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

ideally the chain diff would be a better more efficient solution. but cost is an issue, and im not ready to design a drivetrain and other complex components. in addition i wanted the option of fitting a reversing box in the future. the scope of the project was to build a road legal race car ( eg. ADR3, SR3,XTR2) that used existing components from road cars. the chassis, suspension and body work are of my design and construction, that i feel is something i can handle with my budget and its within my abilities. but i would rather just integrate existing parts at this stage. im not cutting corners on important stuff like chassis rigidity, shocks and tires, but designing a chain drive system to extrapolate an extra 5% out of the powerplant, is just not a priority now.

however i am designing the car to be adaptable to other drivetrains, suspension components, brake systems etc. if i could afford to id fit penske monotubes, a dry sumped hyabusa engine, machined aluminum uprights, 4 piston calipers, full spherical bearing suspension, chain diff, carbon body, and 13 inch 3 peice kodiaks etc. but for now stock parts will have to do for cost reasons.

dont get me wrong, i will do all of the above, but i look foward to developing it over time as oppose to trying to make it perfect the first time round. like you said "its about containing costs"

Andrew

Nice build, nice fabrication and nice philosophy Airframe.

_________________
I'll keep an eye out for you!

To err is human...
I am more human than most.

i have pretty much settled on the same idea for driving the rear end as you have in your car so I'm very anxious to see how it all turns out. Currently I want to find an e30 gen. bmw diff with a 3.15 ratio because they came stock from the factory.

Are you hoping to use the driveshaft to absorb vibration and shock btw. the engine and the diff or are you just using it to save room for the reverse box??

Have you looked into anything like the powertec quaife unit that is in the radical sr3? It's an integrated unit that houses a reverse box, diff, and gear drive all in one case. It's pretty impressive but costs about $5000. I'm almost giving in to using it just because it's so neat and simple. god knows it would elminate the locost out of the project.

How about this: http://www.quaife.co.uk/Quaife-CD-axle- ... riven-cars

It's "only" $3000...

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

yeah I've been looking at that one too, but it still "uses" a chain to transfer from the bike output to the transfer case input. I have yet to get ahold of any dimensions for it to see if there is room to do a direct drive from the output to the input shaft, but from the looks of it there isn't enough room. It can be mounted either horizontally or vertically though which is a benefit for packaging.

only $3000... still beyond my budget. my car will initially be optioned with fred flinstone reverse. ive spent 3800 so far, and 300 is in consumables like reamers, taps, cut off discs drill bits etc. that includes brakes, springs shocks, steel, aluminum, and im probably only about $500 away in steel and aluminum to a complete rolling chassis (sans fuel, electrical, and cooling systems).

yes i did consider the sr3 unit, but for a single component that's lots of money, and just i cant justify it now. but later when i can afford the optimal components, like penske dampers, kodiak wheels and a hyabusa engine i will chain drive it. most like with the quaife unit.

for my application, $290 for an LSD and compatible driveshaft's is an approriate drivetrain solution for my budget.

the engine will be mounted on rubber bushes, the drive shaft will have a slip joint to accomodate for minor changes in lenght.

Andrew

My wife gave a drill doctor last year and it works great. I also have a HBF portable band saw that puts a friction cutter to shame. It’s extremely quiet compared to a die grinder. No sparks fly and no nasty fiber particles in the air to breathe through a painter’s mask.

That’s a good idea making the rear adjustable while keeping the front in close to the same position. Not a lot of room around the pinion flange/ flange coupler/joint area.

Hopefully the laws in your area will allow for a road legal, bike powered car.

For me, the craftsmanship is much more interesting than the actual parts used.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Wow, that thing looks like a Daytona Prototype. I can't wait to see it.

_________________
He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

quick update from july.

bad news first. After three months, I haven't received anything from Racetech.
Ive asked for my money back. Hopefully it will be refunded. I spent over 1000$ on dampers, springs, and rod ends there. Seems strange the owner will not return my calls or emails, we had good communication up until the sale. I understand there is a backorder period on parts not normally stocked by QA1 dealers, but three months is unreasonable. I managed to get my QA1 rod ends from CH engineering within ONE week from ordering.

Anyways on with the progress. Ive spent the last couple of days Ive had off busy working on the rear end. Rear A-arms and suspension pick ups were fabricated. I didn't get to mounting the diff, but thats a good thing, because the more I think about it, the better(and simpler) the design gets.

Ive order(and received) rod ends from CH engineering for the pushrods, rod ends from midwest control(5/8 for outboard lower a-arms) turnbuckles, jam nuts, and more nuts and bolts etc from aircraftspruce, and bushings from BP northwest. Ive also bought a set of wheels for the project from a local seller on craigslist. There 15x6(ideal for a 195/50-15), 4x100 and 38mm offset. they were painted white but Ive begun stripping the paint. they weigh in at 15lbs a piece, a little heavier than ideal but beggars cant be choosers. Apparently the Miata folks reckon that anything heavier than 15 lbs "reduces ride quality". So an acceptable weight for my application until I can justify something lighter and consequently more expensive.