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A few more? Yesss! Thx to killer and the VSO resizer.

Model has one bit of body on it including firewall. The white plastic center pivot part represents out-of-scale the '68 VW part, of thin box section steel which has to be reinforced to take the concentrated stress of a pivot hinge.

You can see that the 3 X 3 center spine holds everything together pretty much along the center line. Engine (that tool box & paint can contraption), driver and passenger are off-center but sort of balance each other. More on tilt and balance after I test it! Be patient.

I forgot to mention the hydraulic pump in the closeup. It has two pairs of sprockets, two chains. Right behind the larger sprocket there is a slider on the shaft to engage one set or the other to the pump/motor. Normal is pumping into an accumulator tank; reverse is drawing from the tank to drive the car backwards.

It's good to see some pics.

Do you have adequate ground clearance at 30 degrees of tilt if you go through a dip in a curve, compressing the suspension? The tilt limiters could be on top with rubber bump stops on top of the vw frame horn.

_________________
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

The 30 degrees, or 27 or whatever it ends up, puts one edge right on the ground. So yeah, tilt limiters are in order here, and maybe a little wheel or a skid on each side to hit the street at the max.

I just ordered a piece of one & a quarter dia dom tube for the driveshaft. The piece in the pic is too heavy. Wish me luck in making it work. Am considering using shaft clamps to fix the ends and center bearing journal, if enough friction can be had by clamping. Could that be adding too many points of potential failure?

It would be more beneficial to handling if the occupants sat higher in order to use the greater lean angle, moving the cg further to the inside of a curve. With tandem low seating, it could be narrower to allow for 30 degree lean without contact.

Driveshaft weld yokes are a press fit into the tubing and are then welded. I don't know what clamps you could use that would be adequate to squeeze .083" wall dom and not unbalance the shaft.

_________________
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

Tandem seating means both occupants have to straddle the drive shaft, seats at least six inches higher. You're right, this may improve balance and make the cg movement more bike-like. It would also extend the length/wheelbase unless I cram engine, two people and the rear wheel into a tight line. I'll stay with the side-by-side low seating on this first attempt and see how it works. Ground clearance can be increased if need be.

If I press fit and weld fittings-to-tube , the center bearing will be stuck in place, not removable; right now it is (to be) on a short rigid piece connecting front & back halves of the shaft w/no flexible couplings either side. I want to be able to remove the drive shaft without disassembling a U-joint or the swing-arm. One end may have to have a pair of bolted flanges. Still open to all options. Thanks for all your input here.

Two piece sprockets are available. Is sprocket replacement the reason you want the shaft to be easily removable?

_________________
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

Yes, not only sprockets but other machined bits that make up the engagement & drive mechanism in the hydraulic drive part. These are all "experimental". Would you expect that the first time they are installed and running they'll be perfect? Or the second time or the third?

Actually, I would. Installing the sprocket with the correct alignment and tension seems straight forward to me. The chain can be taken apart so the shaft would not need to be removed. I don't see anything experimental about driving a pump with a chain and sprockets.

_________________
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

Thx for the vote of confidence Mv8.

My new shiny shaft/tube arrived today. Instead of cutting it in two and adding a bearing journal I may just slide the bearing on from one end and fix it in the middle somehow. End fittings can be welded as was suggested (press fitted to the tube and all), but with some means of removal yet to be determined. I'll use either a 1.25 bore bearing and cause enough clearance to push it to the right position, or I'll start with 35mm ID and cram in a shim to center it on the shaft. Mounting it to the frame is really fairly simple; two parallel fine threaded studs with nuts under a two-piece bearing retainer sandwich to snug it up, then two more on top. Clearance around the studs will let it self-align.

Here is another question I'm toying with: front (VW) brakes are hydraulic and I have all the stuff to connect them, etc. The rear is mechanical linkage, normally direct to the pedal on the right side of the bike. I could use a hand lever to actuate this in the car but I don't like the idea - no balance. Or two brake pedals working in unison . Not good either. Maybe I can rig a small hyd. cylinder on the rear linkage, along with manual for parking.

OK here's another question. The U-joint angle in the rear exceeds 10 deg., may even get up to 12 deg. which is too much from what I've read.

Adding a chain drive between engine output and drive shaft would move fwd end of dr. shaft over to the centerline and down some, reducing that angle to well within limits. It would also allow me to add an overdrive ratio, reduce cruising rpm from 4500 to 2500 or less at 70mph. Higher engine speeds can be used in the lower gears for hill climbing or whatever, but I do love the way my Honda Odyssey can cruise the highway at 2000 rpm.

So the added 2 sprockets, chain and another bearing, and the elimination of one U-joint in the process, seems easy enough to me in order to achieve these two advantages. (Third advantage is that the drive shaft is centered better and intrudes less in the cockpit. Fourth advantage is that the engine can be scooted further to the right for improved weight balance.)

Drawback besides a little added weight: getting a drive sprocket adapted to the output spline on the transmission. It is possible that Yamaha has one of these somewhere for this engine or a similar one; I don't know yet. Otherwise I may cut the existing U-joint yoke and machine it to accept a drive sprocket. It is hard steel and I'd rather not try that.

Any suggestions are welcome.

I didn't see any mention of an accumulator, which should be large. The pump isn't turning when your stopped. Are you using a variable displacement pump?

It's more practical to use a fwd transaxle or vw beetle transaxle backwards upfront with rabbit half shafts and uprights, combined with an adapter to fit the engine of choice and a pump driven at engine speed.

_________________
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

Yes an accumulator, approx 2 gallon tank rated at 3000 psi, enough for 300 feet or so of reverse travel.

Your 2nd para about VW half-shafts etc. makes no sense to me. Gear reduction, direction of rotation and all that is taken care of by the bike parts, EXCEPT I am now seriously considering adding a bit of overdrive by offsetting the engine from the drive shaft, using 2 sprockets and a chain between them to get the final ratio I want.

Fwd eliminates the super long driveshaft and clearance issues. A hydraulic pump can be added as an engine-driven accessory, allowing pressure to build even when stopped. The accumulator will bleed down over time. How long will the accumulator maintain operating pressure after you’ve stopped? How far and fast will you have to drive before you can lean or reverse?

I guess you will regulate the output to around 1,000 psi. If the 2 gallon accumulator is full at 3,000 psi, about 1-1/2 gallons are useable at operating pressure. The motors I’ve seen are all rated at a flow rate of 9 gallons per minute at 1,000 psi, so reverse should work for about 16 seconds if geared for the motors rated torque.

_________________
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

Your time-in-reverse numbers are in my ballpark; I can project about 30 sec of backwards running time on a gallon of fluid using a Haldex pump/motor of .258 cu in displacement. I have 5:1 reduction from reverse motor to shaft, then 2.9:1 more in the rear end. At 120 wheel rpm, motor speed is 1740 rpm, using 2+gpm of fluid.

As for front wheel drive, I'd consider it more if I were at the beginning, but...with current VW '68 bug front axle, hinge pivot mechanism, frame to match, and a working Virago rear drive, it is MUCH easier to rig the drive shaft etc. from front to back. Original plan: combine motorcycle with a 2-wheel front axle, build a body around it, and voila, I'm off to the races. Then I added tilting, which complicates the whole thing, but not too much.

I'm really looking forward to learning tilt control by way of weight shifting to actuate a little hydraulic valve under the seat. I'm thinking that ought to be self-correcting - after I get the hang of it anyway.