Author Topic: Getting a tacho drive fixed on a classic racing bike  (Read 37766 times)

Offline Stilldrillin

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #50 on: September 24, 2009, 03:47:00 AM »
I've really enjoyed reading this thread John, and learnt a lot (as usual), thanks  :clap:

CC

Me too an all..... 

Thanks John.   :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Gerhard Olivier

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #51 on: September 24, 2009, 03:54:23 AM »
Bogs i dont understand car and bikes much but WOW

THat was a good bit of engineering thanks lots learnt

Gerhard
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bogstandard

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #52 on: September 30, 2009, 02:02:54 PM »
Another couple of hours shop time snatched and I managed to get a fair bit done.

This bit was done the other day, but I couldn't progress any further until it was done. I had already mentioned about removing the kick start system. The last part of that job was to make up a spacer and dress the gear lever for a nice close fit to the outer case.




Now the gear lever is out of the way, I could now get the two original bits machined to a finished state.
I used the mandrel that I made the nut with, and mounted the nut onto the RT. I then centred the machine quill up to the nut spigot, using a shortened arm that I had knocked up for my centring DTI. It worked a treat, and it now allows me a little more room to play with on the mill throat depth. The Y axis was then locked up solid.




I could have made this slot using a slitting saw, but if I have the chance, I will always choose an end mill (or slot drill). Me and slitting saws just don't seem to get on well together.

By taking steady cuts in the X axis gave me a nice 3/32" slot, plus a couple of thou clearance, because invariably, the cutter cuts the slot slightly oversize.




Slot cut, now for the bit to go inside it.




This was the easiest way for me to hold the part and to guarantee that each side will be exactly 180 degs apart.
Because of the amount sticking out, I couldn't guarantee that each side to be machined would be at the same height, so I treated each side as a new cut, and touched on first then cut down the required depth. I ended up with a blade spot on 3/32" width, and exactly on centre.
I used a high speed cutter with a 1mm rad on the edge, this reduced the stress on the joint between the blade and the spindle. If it was a sharp cut edge, it would be liable to fracture at that point.




The two parts fitted together just nice, with a couple of thou running clearance. You can just see the rad produced by the cutter at the blade/shaft transition.




Again, I was stopped from continuing any further with the tacho drive because there was another repair to be carried out.
Whoever had converted this standard engine to a racing one had done a bodge job on the crankshaft.
To reduce the swept volume of the crankcase, it is standard practice to fill in the sides of the cast crank webs. They had just bodged on round ali plates. The problem was that when the engine started to reach top revs, the unsupported areas of the ali discs started to 'fly' by themselves and rub on the inside of the crankcase. So I have come up with a repair scheme.
I prised out the loose areas of disc and gave them a good clean up. Then they were given a coat on the inside, and all over the outside edges with JB Weld, a metal filled epoxy resin.
Hopefully, when that is fully cured, I will be able to machine it back and end up with a pair of well bonded in discs.




Just got to wait now before I can continue.


Bogs

Offline Stilldrillin

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #53 on: October 01, 2009, 04:00:13 AM »
Progressing nicely John!  :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

bogstandard

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #54 on: October 01, 2009, 04:07:18 AM »
Nicely, but very slowly David.

I was hoping to have had this done weeks ago, but it seems that at every turn, something else crops up.

There is not much else that could rear it's ugly head, so the end is definitely in sight.


John

Offline rleete

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #55 on: October 01, 2009, 07:57:20 AM »
Famous last words.  Never doubt Fate's ability to interfere!
Creating scrap, one part at a time

bogstandard

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #56 on: October 01, 2009, 11:57:39 AM »
Fate has no chance this time, I was in and done before it had got out of bed.

Once I had a few jacking screws between the two main crank discs to stop things flexing, I anchored the conrod to them with plastic coated garden wire.

I found that because the centre drillings had been damaged over the years (mechanics hammers belting on the ends), I had to locate the shafts into the rotating chuck I had made for the tailstock, and a quick spin up showed that everything was running true.
I set the lathe speed to 190 and did a series of facing cuts across the inset ali discs. Once that was all cleaned up, I set to work with emery tape and sponge blocks and cleaned off all the rust that has grown on things during the couple of years it had spent in a ditch.




After an hour or so, the finished crank emerged. Supported on the high v-blocks I had purchased the other day, I knew I would find a use for them.



Very sorry for the sudden end gents, but nothing else to do now but send everything back to it's owner.

A now happy Bogs, and hopefully, a very happy bike rider.

Offline Stilldrillin

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #57 on: October 01, 2009, 12:29:37 PM »

A now happy Bogs, and hopefully, a very happy bike rider.

Great stuff John!

That`s just reminded me, from a long time ago...... "Happiness is 7,200rpm, in third".......  :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline chuck foster

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #58 on: October 01, 2009, 12:33:30 PM »
thanks for the write up and photos john...............it's nice to see a project through from start to finish  :thumbup: :thumbup:

chuck  :wave:
hitting and missing all the way :)

skype:  aermotor8

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bogstandard

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #59 on: October 01, 2009, 01:19:33 PM »
Many thanks lads, glad you enjoyed it.

It wasn't really a project as such, just a mishmash of different repairs, but as long as someone gets a bit of info that might help them at some time in the future, then it was worthwhile.

I just can't wait to get the shop cleaned up, and get back onto some of my own bits and pieces. I suppose that will take me a couple of weeks.


John

Offline CrewCab

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #60 on: October 01, 2009, 02:14:08 PM »
just a mishmash of different repairs,

But a very entertaining mishmash John, I just love the way the cranckase now looks "original", not an add on like before   :thumbup:

CC

Offline CrewCab

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #61 on: October 01, 2009, 02:33:01 PM »
In fact I've enjoyed it so much I've just been back and read it all again  :bow: lovely work John, and, as you said earlier , helps preserve our heritage, hope your customer/pal appreciates ho much work has gone into the job  :thumbup:

CC

bogstandard

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #62 on: October 01, 2009, 03:56:17 PM »
Dave,

He has just been down to pick the bits up, he was nearly crying when he saw them.

Isn't it nice to be loved.


John

Offline dsquire

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #63 on: October 01, 2009, 04:05:44 PM »
John

Glad to see that he was as impressed with the work as I was. It is moments like that when you realize again how nice it feels to be appreciated. Every time he looks at that bike or shows it off he will be thinking of you and the fine excellent job that you did on the repairs. :ddb: :ddb: :ddb: :ddb: :ddb:

Cheers  :beer:

Don

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'til your good is better,
and your better best

Offline CrewCab

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #64 on: October 01, 2009, 04:33:02 PM »
He has just been down to pick the bits up, he was nearly crying when he saw them.

Well, with you doing your bit to preserve our heritage and JS planning to be reincarnated as an egg timer you'll both be making your mark for years to come ... and rightly so  :clap:

CC

Offline John Hill

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #65 on: October 08, 2009, 04:50:41 PM »
Yes, very interesting to watch Bogs and a very nice result, no wonder he was pleased. :thumbup:

Now..... I have this little problem with the kick starter ratchet on my Douglas..... I was just wondering... :coffee:



(According to what I have read I will only need a little spacer which I am now well equipped to handle myself.)
From the den of The Artful Bodger

bogstandard

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #66 on: October 08, 2009, 05:12:11 PM »
John,

A couple of bushes and a spacer will make sure you will be bump starting it from now on. Kickstarts aren't required on a racing engine, they are just dead weight.

BTW, he has asked me to go to his shop at some time in the future and help with assembling the engine. That should be interesting, I hate working with other peoples fingers in the same pie. I think I will tell him to get the box of bits, and leave me to it, or else he is on his own.


John



Offline John Hill

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Re: Getting a tacho drive fixed on a classic racing bike
« Reply #67 on: October 08, 2009, 05:30:52 PM »
John, it could be that he is seeking to learn from you.  I suggest you take your Thermos or box of beers and make sure you dont actually put your fingers on the engine,  just by watching and talking you will be able to guide him through which will avoid disaster and ensure he is a very happy chappy having 'done it himself',  that what I would do anyway.
From the den of The Artful Bodger