Vintage BMW Motorcycle Owners

Still waiting for parts but in the meantime the crankshaft trueing stand is progressing.

Mal, I'm quite impressed with your abilities in putting together your own tools and your methodical approach; I'm of course following along with this through my own R69S tear down, but I'm simply working out of my garage; aside from having a few specialized tools, I feel like I'm just rubbing two sticks together...you're a definite inspiration!

I'll keep checking back in to see how you're doing...I'll likely be progressing much slower, as I've already got a huge list of parts I'll need to source and replace. Thanks for posting!

I never know if posting stuff up is helpful or not. If just one person gets a benefit then it has been worth the effort.

The forum is very helpful to me as well and I appreciate that others raise issues that I have not even thought to question.
The flywheel discussion is a case in point.

Regards

Mal
Australia

Mal - Please keep posting. You provide the insight of a seasoned and talented mechanic - machinist.

I for one am interested in the tooling you have available to do the machine work you do. The more work you can do yourself the more satisfaction with the results (and it saves a bunch of money, too).

The teardown I did on my R50 was a lot easier than what you are dealing with - really no surprises at all. I just cleaned the slingers, bored but jugs, new pistons and rings, wrist pin bushings, valve job and clutch. My only surprise was self inflicted as a result of inexperience. I broke the exhaust flange on one of my heads but it was repairable. I am still looking for my next project and I am sure I will eventually run into the problems you have detailed in this thread. A good friend and member has an R69 that could use a re-build. I will be sure he is aware of your project.

I have been off on a small side project helping a friend with an old lathe he inherited.

The trade off is that much of the work I am doing is helping with parts I want to make for the crankshaft trueing stand.

Here is a couple of pics just to prove I have not been having lazy days and not serving the most important R69s rebuild project.

First is a pic of a left hand and right hand trapazoidal (metric acme) thread taps made from tool steel.

The second pic is a small brass screw which will hold up the brass nut I am making for his lathe cross slide.

The taps will be used to thread the feet of the crankshaft trueing stand. The reason for this is that as the new conrods and pins are pushed into the crankshaft webs the run out needs to be regularly checked and adjusted. That means the crank starts out wider and gradually gets narrower. The way I have it planned is the uprights (legs) of the stand will be able to be easily moved together with a small handwheel.
Well that is the plan. We will see how it works out.

Thanks for taking the time to read about it.


Mal

It looks as though the taps are tapered for a part of their length, and then straight.
If so, how did you turn them?
Or is the root diameter the same full length, and just the thread form truncated?
A total length taper could be done with an offset tail center.
CNC machine?
Inquiring minds want to know.
Thanks

No I don't have a CNC machine. I thought about it but Its a lot of money and a steep learning curve with high annual costs for software licences and fairly high redundancy over a 10 to 15 year period because of software updates etc.

So I have an engine lathe, should still be good in 100 years time.

I turned up threads on the lathe, then set the compound slide at 1 degree to taper the piece from minimum to maxium thread size. I allowed that the last 20mm of thread would be the full thread. The taps are long because the thread profile is wide at the tip and needs to cut the thread more slowly than a regular 60 degree thread profile.

I then hardened the steel by bringing to red hot and quenching.
Then I tempered/stress relieved the pieces by heating to sub 600 degrees F and allowed to air cool.

Trust that answers your question.


Mal

Hey Mal..
I've got to admit your posts are really fascinating.
You remind me a lot of Richard Proenneke.. the man who hand built a cabin up in Alaska, built most of his tools and lived off the land.

https://en.wikipedia.org/wiki/Richard_Proenneke

It is a nice association to make but really I am no lone woodsmen.

For one I have an amazing wife who I would have to take with me and then where is the 3 phase power for my shed going to come from, I ask.

It seems like he was an amazing character and thank you for the introduction.

Thank you for taking the time to check in with progress on the refurbishment of our bike.
It has been a lifetime dream to own and work on an R69s, ever since I was just 17 and saw my first example.

So here I am 50 years later living the dream. Better late than never.


Mal

Well I keep getting side tracked and here is another diversion.

New brake linings and a bit of a clean up and tweak of the front brake backing plate and shoes.


Mal