Author Topic: Project "Laubfrosch" - the trials hybrid  (Read 21754 times)

0 Members and 1 Guest are viewing this topic.

grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
on: May 25, 2019, 09:55:11 pm
Well, I didn't know if I'd start a thread about this, but Adrian encouraged me to do so, so here we go.

Behind the project called "Laubfrosch" (German for "tree frog") stands an old, worn out Continental frame an Indian 350cc engine, British gearbox and some spares taken from another Indian Bullet. The goal is to build a small, lightweight and versatile bike for trials riding. Nothing competitive, just for fun and ideally street legal. There also are some goodies, like Fury top yoke, a '40s Smiths Chronometric 80mph speedo, a Lucas MO1 magdyno and a narrow primary housing.

So here is what I started with.
The frame an engine block and gearbox casing:




Quite obviously, there are some areas that wouldn't fit:










So I started by cutting off any parts that might be in the way:






Everything cleaned propperly:






Used a factory made stencil for the radius ;D






Fits much better now:








More tomorrow!
Andreas


mattsz

  • Grand Gearhead
  • *****
  • Posts: 5,525
  • Karma: 0
  • moto-gurdyist
Reply #1 on: May 25, 2019, 10:57:18 pm
Oh, boy, here we go again, just in time!!!



Adrian II

  • Grand Gearhead
  • *****
  • Posts: 2,621
  • Karma: 0
  • Sharing my ignorance with anyone who needs it
Reply #2 on: May 25, 2019, 10:58:23 pm
This was quite a popular conversion in the UK. I sent Andreas the link to a part-finished one for sale on Hitchcock's forum, which has some more interesting pictures, though no S1 Interceptor in the background!

https://messageboard.hitchcocksmotorcycles.com/viewtopic.php?f=5&t=9447

A.



Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #3 on: May 26, 2019, 08:56:22 am
Trying on the magdyno:




Looking good!




Since one of the coolest things about the Enfields is the ability, to remove the top end without removal of the engine, I naturally wanted to keep this feature. So I adjusted the frame to do so:






I also have an old Interceptor tank that might be used here - or an aluminium one?!






The donor for some of the parts:




The whole rear section is going to be used here and fits perfectly into the 250 frame:




A quick mock up with the front end put together - gotta love these half width hubs:




The wannabe- Chopper handle bars fit much better on a trials bike, don't you think?




I also got two packages from Austria:




Inside was a ready-to-salvage 350 parts collection:




As I want to use the narrow primary housing, the crank shaft had to be shortend. So first was the disassembly:










More to come...


Adrian II

  • Grand Gearhead
  • *****
  • Posts: 2,621
  • Karma: 0
  • Sharing my ignorance with anyone who needs it
Reply #4 on: May 26, 2019, 06:26:26 pm
Quote
The wannabe- Chopper handle bars fit much better on a trials bike, don't you think?

Not a bad match, the Fury top yoke looks the business, what parts do you have for the stanchion top fixings?

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #5 on: May 26, 2019, 07:28:17 pm
Hi Adrian,
I found the original bolts/nuts/gauze-thing that belongs there in a box that I got with the Interceptor! I'll show what I've done with it soon :)
Andreas


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #6 on: May 27, 2019, 09:27:49 pm
Well, not that much participation here, so let's tickle your imagination a bit more ;)

As I wanted to use the Fury yokes, but didn't have a handle bar clamp and these are unobtainable, I thought I might just make a pair... Why a pair? Well, I need something to clamp the first one to, so why not just make two of them? ;)












Next will be the fork stanchions ;)


Adrian II

  • Grand Gearhead
  • *****
  • Posts: 2,621
  • Karma: 0
  • Sharing my ignorance with anyone who needs it
Reply #7 on: May 27, 2019, 11:33:31 pm
That is nice work, but check clearance against the top of the fuel tank (in its final position) carefully , I think the factory clamp is a bit thinner.



A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #8 on: May 28, 2019, 06:27:07 pm
Yes, it will be trimmed a bit.

But first, why would anyone buy a pair of 4" longer stanchions? To shorten them of course!






Only to cut a thread in them to accept the fork nuts!






Also you can clearly see the differences in the types of stanchions. Top to bottom:

-new type
-vintage '50s type
-early Indian type




Turned the lower part to fit the lower bushes used on the old folk legs:




Looking good:




Next I will continue with the crankshaft.
Andreas


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #9 on: May 31, 2019, 11:46:41 am
Still no one interested?

Ok, now here we go...
Completely disassembled the crankshaft:




To make the promary cover fit, I trimmed the end of the driveshaft:




Gave it a centre bore:




And cut a new thread to accept the primary sprocket nut:






As the crankshaft was already in pieces, I thought I might give it a new bronze bush, instead of the weak original one. While waiting for the material, I decided to chop off the passager peg holders:




Naturally I cleaned everything, but I have no picture of that...
When I finally got the bronze, I started by turnign the outer diametre, just a few 1/10mm larger than needed, and contunuing with the inner and a groove for the oil:






Comparing the old one against the new one:




You can see the old one is already damaged:








The new bush is pressed on the crank pin, instead of being a floating one:




Turned the bush to its final diametre, exactly the same as the old one:






Fits perfectly:




And while I was at it, I did a little job on the connecting rod as well:






And finally I reasembled the crankshaft and trued it to just ~2/100mm of runout:




Stay tuned for more...


Adrian II

  • Grand Gearhead
  • *****
  • Posts: 2,621
  • Karma: 0
  • Sharing my ignorance with anyone who needs it
Reply #10 on: May 31, 2019, 06:53:46 pm
Well, I am interested, the rest of us are too much in awe of your skills to reply or have gone off to buy new 650 twins!  :P

Is that leaded bronze for the new big-end bush?

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #11 on: May 31, 2019, 07:22:22 pm
Haha, I'll go with that explanation ;)
The bush is CuSn12 and was recomended to me from someone who has done that some times and he was advised by the creator of the Duese V12. I guess he would know 8)

Doing this wasn't very hard really, I tought it would be tougher.
Some more tomorrow...
Andreas


Adrian II

  • Grand Gearhead
  • *****
  • Posts: 2,621
  • Karma: 0
  • Sharing my ignorance with anyone who needs it
Reply #12 on: May 31, 2019, 09:05:45 pm
Ace Cafe was offering bronze big-end bushes for his Fireball Bullets a few years ago, and John Hutchings of Tollgate Classics in the UK was hoping to offer leaded bronze bushes if he could buy the material in reasonable quantities, so there is a good precedent for this material.

One advantage is that if the bronze bush DID fail it would not spray sharp little pieces of steel roller all over the inside of the engine.

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...


grumbern

  • Grand Gearhead
  • *****
  • Posts: 526
  • Karma: 0
Reply #13 on: June 02, 2019, 09:01:08 am
I'm in good hope, it can't be worse than the original bearing ;)

The engine block was milled in the back, to provide a flat surface for the magdyno mount:








This now is a little too low, but can be kompensated with  sheet metal:




I also made an engine stand (actually, it's five of them):




The broken steering stop was repaired:




Worked a bit more on the front mounting plates:




Also straightened the lower yokes, as these were bent back by at least 5mm!






Now it was time for new bearings, so I put the engine halfs in the oven:




Ready for reassembly:




I fitted the magneto drive gear with a bearing inner ring to give it a hard enough and smooth surface for the seal:




That's it for now.
Andreas


DavidGraves

  • Grease Monkey
  • ****
  • Posts: 292
  • Karma: 0
Reply #14 on: June 03, 2019, 03:22:50 pm
Ever bake cupcakes in the oven ?

Curious how one would align the two parts of the crank ?

Did you have to make a jig before separating it ?

My real question would be how do you adjust it if you press it together a bit off ?

David Graves