Oddball engines and prototypes

[Frits Overmars]

Would like to see that Grumph, you flipping it through the double chicane at high speed and then opening it up coming out on to the back straight with the front wheel pawing the air and the engine screaming (at about 2000 revs). What a spectacle!
Hang on, the front wheel wouldn't be pawing the air, it's front wheel drive!

I once got involved with front wheel drive two-wheelers. With no suspension at all, no wheelbase to speak of and hardly any brakes, they were perilous to say the least.
But seeing our bike laying down black marks accelerating out of corners was quite enjoyable. It wasn't because of the power (only about 10 hp due to the moderate state of tuning demanded by the no-gearbox, no-clutch direct drive) but because the acceleration unloaded the front wheel to such an extent that it started spinning.
Below left the original Solex, right the lunatic version .

[WilDun]

Yes, the fixed pad is retained by a screw. The pad in the piston end seems to be press fit.

Ok that'll be the one I'm trying to describe ........ around 1969 - 70 I guess.

[WilDun]

Will, you shouldn't believe everything you read (except when I wrote it, of course ).
....... that 50 cc Honda twin's internals: 8 speeds.

...... the 9-speed Jamathi box, a wonder of simplicity compared to the Suzuki.
Attachment 335679

Oh well, can't get it exactly right all of the time, but as I said way back, have a stab anyway and if it's somewhere in the ballpark, then someone will be glad to put it right!
(I did think I was a little closer to tell the truth!) - no wonder they had to keep the clutch slipping!

The Jamathi gearbox is reminiscent of an Italian (ISO) scooter which I dismantled (or maybe even a Norton box, as found in lathes). Is the selector actually a rod with dogs sliding inside one of the shafts? - the input shaft?

[T.W.R]

I'd have liked to have seen it myself, LOL. I suspect that with the 28 inch wheel needed to get the gearing, the rotational inertia would have been awesome...Probably need those long wheelbarrow bars to get it to turn. I was never any good at wheelies though so that would have suited me.

Even beating up Hororata would be worth it for the sound



These two were in the follow up clips too....Pavel Malanik Reproductions

[husaberg]

Even beating up Hororata would be worth it for the sound



These two were in the follow up clips too....Pavel Malanik Reproductions

youtube_share;hRs7SUFfZM4]https://youtu.be/hRs7SUFfZM4

The big JAP a guy in the UK was going to start doing one of those as a project about 20 years ago
He had done a rather tasty designed Hardley with a huge spine frame that doubled as a fuel and oil tank.
it was about 12 inch spine and looked a lot like a Cyclone board tracker.
wonder if it was the same guy

[T.W.R]

The big JAP a guy in the UK was going to start doing one of those as a project about 20 years ago
He had done a rather tasty designed Hardley with a huge spine frame that doubled as a fuel and oil tank.
it was about 12 inch spine and looked a lot like a Cyclone board tracker.
wonder if it was the same guy

Could be? I just followed the upcoming clips from another video of the Dennis Franz V8 motorcycle....looks like that Pavel Malanik specialises in doing re-pops.

Thought Dennis Franz was the chubby cop off Hill Street Blues though

[Grumph]

The big JAP a guy in the UK was going to start doing one of those as a project about 20 years ago
He had done a rather tasty designed Hardley with a huge spine frame that doubled as a fuel and oil tank.
it was about 12 inch spine and looked a lot like a Cyclone board tracker.
wonder if it was the same guy

I can't see any of those vids on this computer so I'm guessing here. Is the "big JAP" a V twin ?

I know of two being built in NZ. You can buy a kit of castings if you know the right people - but drawings are apparently very,very hard to get.

[husaberg]

I can't see any of those vids on this computer so I'm guessing here. Is the "big JAP" a V twin ?

I know of two being built in NZ. You can buy a kit of castings if you know the right people - but drawings are apparently very,very hard to get.

Yeah the video is a big one though, 1909 2.7 litre

[Grumph]

I once got involved with front wheel drive two-wheelers. With no suspension at all, no wheelbase to speak of and hardly any brakes, they were perilous to say the least.
But seeing our bike laying down black marks accelerating out of corners was quite enjoyable. It wasn't because of the power (only about 10 hp due to the moderate state of tuning demanded by the no-gearbox, no-clutch direct drive) but because the acceleration unloaded the front wheel to such an extent that it started spinning.
Below left the original Solex, right the lunatic version .

I'd think chainsaw racing is marginally safer....I was once loaned a copy of Motocyclismo (spelling ?) magazine which had a pic of a racing Velo Solex.
No pedals, radically dropped bars. no race pipe. Must have been French....

[T.W.R]

I can't see any of those vids on this computer so I'm guessing here. Is the "big JAP" a V twin ?

I know of two being built in NZ. You can buy a kit of castings if you know the right people - but drawings are apparently very,very hard to get.

Yeah the video is a big one though, 1909 2.7 litre

This one here Greg

[WilDun]

This one here Greg

Some great machines, but I think that the sound of the Megola is fantastic, seen many pictures of it before but had never heard it.

[Frits Overmars]

The Jamathi gearbox is reminiscent of an Italian (ISO) scooter which I dismantled... Is the selector actually a rod with dogs sliding inside one of the shafts? - the input shaft?

Close. Your description is spot-on; only that rod was in the output shaft. Lotus even tried this system in Formula 1.
There must be an English name for this type of gearbox but I don't know it. Do you?
Dutch: trekspiebak
German: Ziehkeilgetriebe
Italian: cambio a crociera scorrevole
Which also demonstrates which is the most economical language . Admitted: Italian is the best-sounding of these three.
Below the 9-speed Jamathi box of 1964 and the Bultaco box of 1977 when it had been mandatorily reduced to six speeds.

[Frits Overmars]

By the way, the hideously expensive seamless-shift gearboxes in the Honda MotoGP works bikes are based on the same principle.
The clutch and the primary gearbox shaft of the Honda gearbox are quite conventional; they could have come out of an old Maico, Zündapp or Simson engine:


All secrets are brought together in the secondary gearbox shaft:


This secondary shaft looks like a cylinder from a security lock, with pawls that are operated from the inside by a rod that slides through the hollow gearbox shaft:


The essence of the Honda box can be seen in the picture below. The pawls in the shaft connect and disconnect the gears to the shaft:

In this drawing a tumbler Rao connects the gear to the shaft when the gear is rotating clockwise. And a tumbler Rbo is connecting the gear to the shaft when the gear is rotating anticlockwise. So in this drawing the gear is locked to the shaft.
The tumblers are governed from within the shaft via an axially moving rod.

Now if we perform an upshift, the shaft will need to rotate faster than the gear. Let us assume that the shaft is rotating clockwise. So we need to retract tumbler Rbo. Now the gear can still drive the shaft, but the shaft cannot drive the gear any more.

Next we engage tumbler Rao of the next gear, so it can also drive the shaft. Then we retract tumbler Rao of our original gear, so it can now freewheel in both directions. And finally we engage tumbler Rbo of the next gear so that it is now locked to the shaft.
That's all, folks: transporting torque from the gears to the shaft without interruption, both while shifting up and down.

Honda has filed patent applications for their seamless gearbox in Japan and the United States (patent applications 2010-203478 and US20110023639, respectively).
You can download the US patent document here: http://www.freepatentsonline.com/y2011/0023639.html

[Grumph]

Close. Your description is spot-on; only that rod was in the output shaft. Lotus even tried this system in Formula 1.
There must be an English name for this type of gearbox but I don't know it. Do you?

Rod and pawl is probably close enough - but I preferred the name the Lotus box earned - the Queerbox.

I suspect that the materials and machining technology of the time limited the torque and HP cpacity of that layout.
I have no doubt Honda have made it work with large amounts of Money...

[Grumph]

This one here Greg

Thanks - that's a cycle pacing machine. I've got a pic here somewhere of the biggest parallel twin you've ever seen driving via a flat belt about 100mm wide.
That's also a pacer.