Tall gears for Daihatsu-Ural - latest mods

[mark_in_manchester]

Hi all -
I thought perhaps someone out there might like to know that 993cc Charade Turbo engine will pull a modified Ural 4th gear at 1:1 (from memory original is approx 1.3:1) running through a final drive bevel box at 3.2:1 (highest Russian ratio is 3.8-ish:1). All parts available from 'Oldtimer Garage' in Poland, who do a good mail order service / web shop, but are probably more expensive than other suppliers. Building up a reliable box is tricky, especially with the later (vertically split) casings as opposed to earlier box which loads gears from the front, using a removable plate which forms part of the flywheel enclosure. Anyone wanting full tedious details is welcome to get in touch. With a 19" back wheel this gives 100kph (60 mph) at about 2700 rpm, and red line (about 5000rpm) equates to 109mph.

I took this out today for the first time - acceleration is down as might be expected, but is still quite adequate. I'm aiming for reduced revs and better fuel economy. Top gear will pull from 20mph (v. snatchy) and 35mph (smooth). I don't think I'll be exploring the upper reaches of the performance potential until I've finished my hydraulic front brake conversion - still on 8" SLS drum. Still, if it was good enough for a BSA Gold Star... No sign of running out of steam when keeping up with / overtaking fast motorway traffic, where upright riding position (pull-back bars) make things unstable / uncomfortable - this thing might even benefit from flat bars and a cockpit fairing (!!). Also front wheel turns out to be very considerably buckled, so it's back to MZ power while swapping wheels around and wondering if I'll be able to true it up.

Mark, Manchester, UK

[Tetronator]

By the powers invested within me!... I resurrect this thread.


Tell me about those gearbox differences, seems one is more reliable than the other.

[mark_in_manchester]

Oooohhhhhhh...diesel bike resurrection has risen to the top of the massive job-pile.

here:

http://www.russianbike.co.uk/viewtopic. ... 8117#p8117

...are some pictures of my attempts to get a Dnepr gearbox together to replace the (reliable, as it turned out) Ural box referred to in the OP of this thread. The Dnepr box allows 3rd and 4th to both be changed - Ural, 4th only, which gives a really big gap between 3rd and 4th. Not so good for overtaking caravans on 'A' roads, which is what I do a lot of.

Now the technical problem where I need your advice:

Dnepr shaft has a 5mm-wide keyway in it, with a key in it (a circular segment) which is a very snug fit. When the flat part of the key is arranged to lie parallel to the shaft, the key protrudes 2mm from the shaft surface.

The (new) 1:1 top gear is a press-fit on the shaft, and also has a keyway cut in it. But unlike the original gear, which was a good fit on the key described above, the new gear has a keyway of width ~6mm and height ~3mm. This means that the a gap about 1mm thick exists on two of the three surfaces where key and (gear) keyway should adjoin.

What to do?

* Fill gap with some exotic 2-pack putty....?!
* Make a mild steel 'L' strip to try to fill this gap?
* Harden it !!???? (like it'll go in without shattering if I do)
* Fill the gap by banging something soft in (copper wire? lead? Al?) - relying on gear being tight on shaft, and ends of gear keyway being sealed by other stuff on shaft, to have 'confidence' soft stuff is not going to get out. But...perhaps it might pulverise and escape as powder in the oil over time?
* Mill a groovy stepped key and harden it (OK, I could perhaps just about to this) which is 5mm (thin) where it sits in shaft and 6mm (thicker) where it fits in gear.

When I first put this together a while back I crushed alu strip into the gap - but I've pulled it apart again as I'm not confident. What do you think?

[pietenpol2002]

Your concerns are well founded. Key stock should be of similar material and hardness to the shaft and gear. Stepped key stock is readily available here in the States for the application you describe. I might think you would find them in the UK as well. Enter "stepped key stock" in Google Images for examples.

[mark_in_manchester]

Thanks Ron

I slowly filed out a stepped key out of mild steel this morning. It's not a bad fit. Opinion on the web seems to be divided between your idea - that key needs to be hard so as not to get eaten by the sharp edges on the shaft and gear as it moves (yeah, it's a really good fit ), and the idea that most of them 'as found' are soft - as in the one which came out.

I have some kasenite at work, and I could try to case-harden it. What do folks think?

[gearhead1951]

A proper "case" hardening gives the best of both , a hard and durable surface with a softer interior for "toughness" !!

[mark_in_manchester]

Indeedy! Well, if you check out the thread above, you'll see this turns out to be not the greatest of my current problems...but we are slowly moving forwards

While on the subject of Dnepr / Ural gearboxes and shaft drives, here's another thread which I've been writing over on the Cossack forum about these issues, and which might turn out to be useful to builders of diesel bikes. It's all about the different length drive shafts employed by various Urals and Dneprs, and my attempts to find some combination which allows me to use both Ural and Dnepr gearbox (not at the same time!) without modifying the frame when swapping from one to another.

http://www.russianbike.co.uk/viewtopic. ... 8125#p8125

For reference - Dnepr MT (with reverse) box is a straight swap for Ural M63/M66/M67 box, but IS 18mm LONGER.

cheers
Mark

[mark_in_manchester]

Well, I had to knock a wall down in the house so that slowed things down a bit. But Dnepr box is now in, with spare (unknown quantity) charade engine. Let's see what happens next!

[mark_in_manchester]

So - the Dnepr box with 4th pair turned around and ground on the flanks to work as a new '3rd', and a new 1:1 top gear pair from Oldtimer garage in Poland, turns out to be a success. The ratios are well-spread, and the bike pulls (new) 3rd well when overtaking before going back up to top. One small problem is that I seem not to have shimmed it up properly - under heavy load (when seeking 'top speed' ) it sometimes jumps out of top. This will probably mean that the output shaft is too far forward in the box, meaning that engagement of the 3rd-4th sliding ring is not deep enough on the 4th gear dogs. So...when I get a little time, out it comes again!

[Tetronator]

Good to know, that's exactly what I've got planned out! Tell me about the shims once you get to it.