Author Topic: Timing side bush  (Read 1342 times)

Online Bsareg

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Re: Timing side bush
« Reply #15 on: 19.11. 2019 00:02 »
It's not that hard to scrape the bronze bush into line by hand. Just need a push fit drive side bearing and patience. I can't remember how many I've done in 30yrs, but no problems.
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Online mikeb

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Re: Timing side bush
« Reply #16 on: 19.11. 2019 02:28 »
Quote
fear only of destroying a perfectly good bushing.
Richard - the more you mess it up then the more toys you will get to play with when fixing it - what a great workshop to have access to!
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Offline BSAmoto

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Re: Timing side bush
« Reply #17 on: 25.11. 2019 20:07 »
Richard - make sure that the machineshop replaces that pic of the long-haired girl on the mill without any haircover.
regards

Online RichardL

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Re: Timing side bush
« Reply #18 on: 25.12. 2019 23:21 »
Well, Folks, I did it. After viewing the excellent video by A&G Engineering about four times, I bucked-up and went for it. I guess the method amounts to "line boring," but not sure that is the correct term. Basiscally, with the crankcase bolted together, run a dial indicator around the inside of the outer race to about 0.0002" within center of the mill quill. Remove the drive-side half, then bore the bush. That almost makes it sound easy, but being a novice machinist, the setup took me about 4-1/2 hrs.

Before I even clamped the timing side to the mill table I measured the slop in the quills of the two mills available to me. Days before, I turned a test plug 0.0002" under the journal diameter so I would know that the next adjustment of the boring head should be the last. After the timing side was clamped to the table, I verified  square with the quill in both the X and Y axes.  From what I could tell, A&G only checked the X axis (not to say I could do this better or, even, as well as the gentleman).

When all was done, I finished at 0.0013" +/- 0.0001" over the journal diameter. The finish in the photos looks rougher than it feels and I doubt a mirror finush is required. Clever observers may see a little glitch (like a shoulder) at the end of the bush that is about 0.002" deep (on the diameter) and 0.020" long. True confession is that I miscalculated the last adjustment but caught myself before running further in and destroying the bush (and all the setup time).

The bush fits very well over the journal but, fact is, I'm yet to put the cases together since the machining, so, I'm yet to prvove smooth movement when assembled. Last time I was at the machine shop I tried to turn a dummy bearing for testing shim fit, but that went horribly wrong due to my material being too hard for the cutting tools (four hours I'll never see again).

I have more pictures I might share, but out of time right now. Thanks for reading and advising what I've done wrong (or, even, right). The only damage right now would be to a replaceable bushing.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online BSA_54A10

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Re: Timing side bush
« Reply #19 on: 26.12. 2019 00:23 »
Richard,
That was not wasted time, it was 4 hours of learing.
Being over precise is a trap we all can easily fall into
We have to always remember that when new the bushes were replaced in workshops which would not have had so much as a micromerter let alone a micrometer with 0.0001" incriments.
They did as previously mentioned, offered the crank to the bus with a touch of bearing blue ( if they were a precision shop ) or a touch of blue bag in oil.
The crank got pulled and the high spots treated to 2 strokes of the scraper ( usually a dull file ground to a sharp edge ).
This process got repeated till the crank when into the bush.
If it spun freely, job done.
A better equiped shop might have an adjustable reamer which was set a 1/2 turn tighter then the od of the crank then reamed, Crank offererd up , if it spun ( and it shouldn't have) then it was job done, If not the reamer got a 24th turn bigger and the bush reamed again, this gets repeated till the crank will drop freely into the case.

Calculators & computers have us believing that sizes need to be accurate to the 5th decimal place when in the day it was "just slides in then drops easily in"
Race engines had the luxury of being accurately measured but ride to work plonker, near enough is fine.

Having said that the extra precision will not hurt anything but just dont get stomach cramps worrying about .0005" .
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Trevor

Offline Greybeard

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Re: Timing side bush
« Reply #20 on: 26.12. 2019 12:28 »
I'm pleased to read about scraping the bush. I scraped the white metal big-ends on my Austin Seven.

Online RichardL

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Re: Timing side bush
« Reply #21 on: 26.12. 2019 12:37 »
Trev,

Thanks for the thoughts. Like GB, my big take-away from this is bluing and scraping, thus answering the question of what to do if the crank is too tight when sandwiched in the cases.

Richard L
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online BSA_54A10

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Re: Timing side bush
« Reply #22 on: 27.12. 2019 02:24 »
If it won't spin freely when bolted together then pull the crank out blue it and slip the crank back in BUT DO NOT TURN IT.
The high spots will leave a line.
Only after the lines have all gone then you can start with the revolutions.
If it is tight in the bush it is prudent to pull the crank rotate 120 deg then try again and repeat one more time.
If the "high spot " remains in the same position on the crank, then the journal is not round  .
If the digh spot moves with each test then the journal is out
If the high spot is always at either edge of the journal then the aligment is out .
Bike Beesa
Trevor

Online RichardL

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Re: Timing side bush
« Reply #23 on: 12.01. 2020 17:20 »
In the continuing story of doing my own machining at the DIY maker's space, I've made the next bit. Bear in mind that this tale is aimed at the less skilled machinists (or nonmachinists) among us, like myself. The master machinists will yawn.

After boring my timing-side bush to size, I decided I wanted a dummy main bearing for the purpise of fitting shims by trial and error without needing to press-on and pull-off my new bearing for each unsuccessful fit. I wanted to just crudely grind out my old bearing for this purpose, but the two bearings are different ODs. In the pictures you can see the cylinder I turned for this purpose. Being an amateur, my first attempt was a complete bust due to using a material so hard that I burned through two cutoff blades before moving to the horizontal band saw, which meandered its way into the critical zone. New part was almost OK, but the landing zone that would sit on the outer-race lip was not perfect and it wobbled about 0.010" Ended by surface grinding both sides. It made the height undersized, but I've measured that versus the bearing and will compensate.

Regardless of that long story, still haven't made the first test fit. I'm slow.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline RDfella

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Re: Timing side bush
« Reply #24 on: 12.01. 2020 18:12 »
Slow maybe, but better than rushing into it and making a disaster. You're doing just fine.
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Online BSA_54A10

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Re: Timing side bush
« Reply #25 on: 17.01. 2020 06:15 »
No need for steel here.
Any hard plastic will do and will be a lot easier to machine.
When we did the A 10 Shane bought a piloted reamer.
I cast some resin filler into a spray can lid then machined it down to be a push fit in the outer race.
Truth time, the 2nd one was a push fit.
The plug was then bored out to take the reamer.
End result
A crank that you can spin between your fingers with 0.00075 float.
Bike Beesa
Trevor

Online RichardL

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Re: Timing side bush
« Reply #26 on: 17.01. 2020 12:20 »
No need for steel here.
Any hard plastic will do and will be a lot easier to machine.
When we did the A 10 Shane bought a piloted reamer.
I cast some resin filler into a spray can lid then machined it down to be a push fit in the outer race.
Truth time, the 2nd one was a push fit.
The plug was then bored out to take the reamer.
End result
A crank that you can spin between your fingers with 0.075 float.

That's funny, because the material for the dummy bearing was free for the taking from the DIY shop and a plastic rod of adequate diameter was available. I guess I could have saved a lot of time, but done is done, and with suface-ground precision.

For your end float, do you mean 0.075mm or 0.00075" with a couple of zeroes missing? I'm thinking the former, as I seem to recall reading minimum float at 0.001".

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

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Re: Timing side bush
« Reply #27 on: 18.01. 2020 02:28 »
Corrected 3/4 of a thou, measured using a dial gauge bolted to the cases and a long bar applied to the other end.
Bike Beesa
Trevor