Rear sprocket/drum (2013)

Bradley, thats a very good thought, 5 or 10 years ago that wouldnt of been viable , but the advancement in CNC machining in the last 2-3 yrs is unbelievable and well worth consideration. My item would not be considered complex or a challenge for most up to date companies, with the fast measuring equipment available
now, it makes producing parts so much easier. I sometimes make a sample (alloy) then have the dimensions recorded at my local CNC machine shop on a Mituytoyo digital reading machine, then have my item cast and
return the castings back to the machine shop for machining, it works well,
I have no experience in steel castings but have no doubt a good foundry would be a one stop shop from start to finish. there is a million of them out there looking for business.

hello Madass

yes.CNC is really mind boggling what can be done. not by me though, I cant even turn one on. I am just an old dinosaur used to manual machines. CNC makes the difficult easy. those double ended chuckers with live tooling and auto transfer, like something out of science fiction when I first saw one. however the cutting principles have not changed except they now rev like a Norton.

thats the beauty of K1045. soft machining but can take heat treatment. this is a very suitable grade with proven performance. must be killed though.

when normalised, machines beautifully. flame hardening is also a simple process.

anyway something to ponder over. comes down to the most economical method, castings or blanks

mate, i will leave you to it now.
best wishes
Bradley
PS are u a Queenslander. state of origin soon

i've sure thot about that drum groove and cover plate lip, its not really needed as oil and grit don't get inside to matter. was planning to drill holes in the friction surface too like we do the rotors for mass and cooling.

Rear sprocket/drum

On 5/9/2013 4:58 PM, Toll Fast wrote:
> On the lesser marques I have no idea.
> On the high quality bikes that BSA made they were nikasil as I have already stated.
> Nikisil is a hard facing alloy and if you have ever tried to machine a BSA drum you would have found out they are so hard they can only be ground.
> This means that they can also be quite thin thus dropping the weight.
> Some pre WWII drums were straight grey cast and all WM 20's were plain cast but as soon as supplies were available BSA changed back to nikisil.
> I have heard that Triumph changed after the take over but not having machined a Triumph drum I do not know.
> Bike Beesa
> Trevor

Much like your front brake, perhaps instead of just addressing the cush drive concern, how about a whole solution. New cush drive and rear disk solution (with replaceable sprocket). Something much more elegant than the MkIII and a LOT lighter. Just make it bolt on to the pre-MkIII swingarm.

A super simple hub with lightweight disk and caliper.

swooshdave said:

Much like your front brake, perhaps instead of just addressing the cush drive concern, how about a whole solution. New cush drive and rear disk solution (with replaceable sprocket). Something much more elegant than the MkIII and a LOT lighter. Just make it bolt on to the pre-MkIII swingarm.

A super simple hub with lightweight disk and caliper.

Click to expand...

Didn't Kenny Dreer do something along those lines at some point of his VR880? Have you got pic's?

Hobot correctly notes we all need two bikes , one stock one do-what-we-wish with.
The bike is just too heavy. The back wheel is the worst of all. I suppose that we
have to order one of each rear now!

Not sure who made it, (painful that craftsmen are not proud enough to put their name on it) but the pin staking was dawg bawls. Fouled on the anchor bolts.

The original, properly staked. Unlike the one shown above, which looks like a crack monkey assaulted it with an air chisel. An insult to metal workers everywhere. Seems they ignored the counterbore feature as well.

Had to take the grinder to it, to cuff down the height.

Labels look familiar?






plate #21 NM E5276 washer qty=A/R
is the shim needed or trim the pins down AFTER INSPECTION
I've been told who supposedly makes them.

I tried two shims. Labarynth seal not even engaged, I could see the brake shoes. Dawg bawls.

I was told by John Healey who supposedly makes them, and coventry spares probably sold yours to Dude.
I don't "KNOW"...it's only second hand from John.
I think the same people that made the soft as butter "made in England" final drive sprockets.

Well, we’ll see if the drive pegs uproot!

madass140 said:

good thinking, if the later cush type were cast iron, the 3 pegs would probably just break out. obviously the reason they went to steel, now what grade of steel ???????

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I've no idea what grade it will be for sure without checking with whoever's getting them made.
I use a cast steel on many large & powerful parts in work & typically it's to A4 or BT1 spec. Neither is especially cheap but it's damn good stuff.
If anyone does know the grade these after market sprockets are actually made, I think everyone would like to know.

Anyone up for the test?

My second rear sprocket/drum was a cast iron one bought from my local British shop, it been on the bike for a few years and the sprocket was still good, one day was going for a ride was about 5 km from home when the the back wheel drum was making a grinding noise the drum had failed but lucky was able to make it home, when I got it apart the end circlip casting had broken well over 3/4 of the grove holding the circlip and the circlip was just hanging there and everything else was all out of place, I ordered a new sprocket/drum from RGM but I was looking at the broken part and thought I might be able to machine the circlip mount deeper and put a larger circlip in so took it to work, it only took me a few minutes to set up on the lathe and using a internal boring bar cutter was able to machine the circlip mount deeper all up with setting it up on the lathe and cutting took about 10 minutes, but the workshop had a circlip kit but the biggest one was 38mm around the same size as stock so had to go out and buy a bigger circlip, got a 40 and a 42 mm circlip the 42mm fitted perfect.
Well that was over 12 years ago and I am still running the repaired sprocket/drum and the new sprocket/drum is still sitting under the bench, for a 10 minute job on the lathe and 2 new circlips was a easy and cheap repair, the new sprocket/drum is all steel, not cast iron, the repaired sprocket/drum has well over 60k miles on it and the sprocket is still good, pays to keep up the maintenance on the chains.

Ashley