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Im Tom, a dutch automotive student. Im planning on building a small sleeper car.

I have been toying with the idea of a bike engine powered mini or Fiat 126 for some time now.
I have also had it in my mind to stuff aa v6 mated tot a vitara driveline in to the mini, but realised it be too much of a squeeze let a lone heavy.

Since im quite capable with solidworks (even if i say so myself). I have modeld some components and thier rough layout on a mini wheelbase and track.



Its a R1 motor which will drive a central diff through a sprocket setup. From the central diff two propshafts will run to the front and rear diff. and these will drive the wheels. I Believe this is the best way and most Locost way of making an awd bike engined car, without running chains.

I am looking forward to all your reactions and ideas.

the greatest problem, in my opinion, is the torque split front to rear with available production pieces. you could use an aftermarket center diff control for a subaru/mitsubushi to control a new venture gears model 140 center diff(about the smallest available in my area, your results may vary) but the torque bias would still be front primary, not preferred by most people, and you would have to mount the diff's upside down (using locally available products ymmv) to get it with 6 forward gears instead of 6 reverse gears which means oiling pumps on each of them, etc, etc. viewed from the front of the vehicle your transmission output shaft is rotating anticlockwise which is a bit of a problem being backwards to most vehicles. the devil is in the details. .. 90% of the car gets built in a day then the "other" 90% takes years.

I will begin building it with normal diffs. Ill look how it drives and probally go for a lsd diff for the center one. I geuss time will only tell if this approach could be reasonable becuase i havent seen anyone try and fail yet.

thats well and good but how are you planning on compensating for the driveshafts turning in the wrong direction?

Bij using a rear diff as a front one and a front diff as a rear one. I could also flip one, but that would require messing around with the inside and oil holes.

Im working on collecting the parts right now, im thinking of using the original mini uprights. This way i can use mini wheels, but it would mean i will have to use the mini balljoints, which can be a pain. Has anyone ever used mini uprights before?

putting the front differential in the back etc works ONLY if you flip BOTH of them upside down. the issue is the side that the ring gear is on in relation to the pinion gear. with a little more research you will find that there is no difference between front and rear differentials other than location and that in normal operation the ring gear is portside in the rear and starboard side in the front. this will not work with a driveshaft that spins anticlockwise as you will end up going backwards at a very high rate of speed when you accelerate rather like an incorrectly assembled vw type1 thru 3 transmission. in addition, using a "limited slip" center differential still does not allow for desireable torque split bias in that the front will become the PRIMARY drive output which is, as i said earlier, a non preferred format. all the "limited slip" center differential will do is limit the amount of slip between the front and rear, bringing the torque delivered to the rear closer to the level delivered to the front WHEN the FRONT wheels lose traction. .. you can get an electronically adjustable center diff but you are still going to be working with the power flow being biased as front wheel drive.
i'm not intending to rain on your parade but you seem to have missed some of the simpler issues. i look forward to an achieveable resolution to the difficulties presented by your choices for drivetrain components

ill look into the rotation of the drive shafts a lil later. But a standard diff as a center one wont favor either side front or rear, right. Otherwise I will have to invest in a torsen diff which can be very expensive. The drivetrain is the biggest issue by far the rest i can take car of no problem.

How would you go about making a Bike engined awd car? would a transferbox from a 4x4 be a beter solution?

a typical (standard) center diff has a preset bias, and is directly influenced by direction of power flow. i'll leave the 1.5-1/2-1/etc discussion alone since it doesn't affect acceleration, just decel. as an example, a 30%f/70%r split is typical in an awd vehicle such as an audi a4 but you are trying to run the front axle off of the rear output of the center diff in the picture you provided creating a 70%f/30%r bias. a differential works by limiting the slip, therefore controlling the bias, between front and rear. one output will always get power, the diff works by limiting the amount of slip between the primary output and the secondary output. it has more to do with the way a differential is constructed than any bias controls such as a torsen unit or even a pwm controlled clutch pack like the nissan atessa system or the mitsubishi/subaru system. if you figure out a packaging that put the primary output facing the direction the input came from you would have it! the problem is you get a lot of complexity and gears to change power flow directions which make heat, noise and power loss. porsche took years to develop an awd system that works well and it still has problems due to complexity even with their EXTREMELY large research and development budget. not that it can't be done less expensively building on what is already available but it is a rather difficult undertaking. maybe have the transmission output drive a gear that powers a driven gear on the input of the center diff but then you end up 1)running the center diff backwards and have to create a new oiling system for it instead of the axles or 2)creating a new housing to hold the trans output shaft(and gear) in line with the input gear and hold the center diff so as that it is once again oriented correctly in the vehicle so that the rear output shaft is once again the rear output shaft(which would mean no more worries with the axles). option 2 is probably easier to create given whats available in todays market, at least on my side of the atlantic but you still have a power loss from making it change direction of rotation.

I geuss u havent quite understood what i meant, im planning on using a standaard rear diff and then mounting it in two bearings and attaching a sprocket. An then running a jack shaft from the engine up to the diff. Just like most mid engined bike powered car setups only turned 90 degrees.

first off my drawing skills reeeeally suck so i'll have to use your provided drawings.
okelydokely, you may be on to a method that is easy enough to construct given access to a small machine shop or a decently equipped classroom. powerflow as follows. .. from output of trans thru jackshaft to "midcase", then a chain to the outer housing (aka carrier) of a diff unit mounted inside the midcase (in appearance resembling a chain drive rear diff used on a variety of bec's). you would be able to mount the carrier oriented so that you would have a choice of bias by which side the sprocket(ring gear) is on inside the case (to the front of the case or the rear of the case) solving the bias issue. all this leaves is the driveshaft rotation direction to be dealt with, which is pretty easy, and providing some sort of lubrication system for the midcase. a small electric pump would work but is yet another load on a rather limited electrical system, a small piston pump can be driven by a lobe on any of the input or output shafts to provide pressurized oiling with tubes directing the oil flow paths or a chain driven pump can be run like a yamaha fjr (for examples you can review the laycock overdrive unit(volvo/triumph/mg/etc/etc) and the ford fmx transmission, they will provide examples of form and function). none of this is impossible to do, as an example we have a member who has completed his prototype of a reverser box already with input from our august compatriots (hows that guys? makes us even sound smart don'cha think ) and i fully expect him to be in production within the year. you are onto a workable method but, like i said, the devil is in the details. keep them ideas coming! and when in doubt remember the only failure is failing to try.

thats why i love the locost spirit. Im selling off my old moped. to make room aan funds for the driveline. I will construct the driveline first, without a car. The challange will be to get it nice and compact. I hope to start collecting more parts soon.

I think the McGill students ran awd on their FSAE cars for a couple of years (at least). As I recall they used a Haldex center diff with some sort of electronic controller and traditional ATV diffs front and rear.

FWIW, the Mini uprights work pretty well on Minis <g>, not sure what issues you have with the ball joints, The old school rebuild-able shimmed ones work fine in my experience but I believe there were some sealed disposable Metro items that fit like for like.

The bigger question I have is why? The FSAE kids get engineering "points" for the added complexity but I don't know why you'd do it on a BEC Mini, the Z-Cars units don't seem to have any traction issues.

Cheers, Ted

First: On the layout and rotation issues, here's a silly question...Why not just turn the engine around so that it can directly drive the sprocket on the differential from the original output sprocket location. This would reduce the complexity, turn the driveshafts the correct direction, and allow you to run both driveshafts in a straight line rather than shooting the rearward drive shaft off at some awkward angle.

Second: I must have missed something in the differential action discussion, where it was commented that the differential would constantly bias power towards one side over the other?? The natural inherent torque split on a mechanical automotive differential is 50/50 until one wheel starts to lose traction, even with a mechanical limited slip. Otherwise RWD cars would be always sending significantly more of their power to one side than the other, even when driving in a straight line...Which obviously isn't the case.

I dunno,nearly every rwd even lightly driven trucks seem to always wear the passenger side tire more the any other tire.I know that tire gets loaded more due to the axle trying to rotate it into the ground but is that the only reason for the wear?.

Turning the engine is an answer, yet all the weight then will be on one side of the car, on the drivers side. This would cause some handeling issues, this is why i have gone for this complex solution so i can have the engine in the middle.

The reason i want to build it awd, more of a challange to myself, i dont want to go with just a normal mid engined mini. Its been done over and over again, and not a really big challange.