The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Daveh67 on 23.09. 2019 09:13
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Hi everyone.
Looking at my timing side bush its a bit diferent.
Looks to have a steel sleve outer with a bush inside.
Has anyone seen this type.
Cheers n beers
Dave
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Other side
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Had one where the pegs holding the two together sheared allowing the inner to turn, cutting off the oil to crank. I only fit solid ones now.
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Its the most common type fitted, usually found on original bikes or ones restored in the 1970's. As BsaReg says, the construction allows the inner bearing material to rotate, cutting off the oil if the retaining peg is absent or shears off. The very early engines had what looked like a white metal bearing in a steel carrier, in effect a one piece bush, then replaced by this type.
To remedy this, BSA moved over to a solid one piece bronze bush on later engines, and this is the best choice these days for replacement. They are available in stock sizes, and some enterprising folks will make you a custom bush enabling a well worn crank to be ground just enough to clean up, even if worn beyond a stock size, and also give a second life to damaged crankcases by boring the bush location, to allow an oversize O.D. bush. In fact it is better to extend the life of the crank by grinding off the minimum, installing an undersize bush and getting it line bored to the running clearance on the crank journal, rather than sticking with stock recommended sizes.
Even if just polishing the journal and installing a new matching stock sized bush, they sometimes need to be line bored....the bush closes down slightly when fitted. Plenty about this already on the Forum.
As this is the new toy, do a bit of research about crankshaft sludge traps, and make sure it gets a good clear out!!!!!!
Swarfy.
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Swarfy, are you sure that BSA moved to a one piece bush?
I have seen many engines pulled down and have yet to see an original one piece bush.
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Yes Trev.... One piece bush found on A50/65. Seager Engineering, Ipswich, Suffolk UK are currently offering 68-0334 (A65 bush 10 thou u/s) as a direct replacement for the earlier composite A10 bush. Current eBay UK listing. They will make you any size you like and offer full machining services.
Not much help to you halfway round the world, but of interest to UK forum members.
Swarfy.
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I have a 1956 A7 and a 1963 A65 and both were fitted from new with steel outer bush. The A7 when I bought it had previously been fitted with a new sleeved bush which was not pinned the bush turned and cut off the oil supply causing some damage the previous owner had this corrected and a new bush fitted which was also sleeved but pinned, this bush only lasted about 2000 miles when I had to strip down myself and I fitted a new solid bush and line reamed it and it is now running ok. The A65 has a pinned sleeved bush in and has been running ok for about 6 years now. If I was to have to fit a new tiiming side bush in any bike now I would go for the solid version.
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cheers for the info. in the process of measuring and will probably go for the one piece unit. i know i can stake the sleeve bush and hold it well but one piece wont have any chance of failure.
the sludge trap is out and crank soaking in de greaser. ive got my new spokes so i will play wheels while a new bush gets fitted and the crank gets a good soaking.
forks are next on the list...... no damage but bushings worn and the fork tubes seem good.
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BSA replaced the original one piece bush in 1957 with the steel shelled version. The insert was a steel strip lined with Vandervell VP23 material rolled and inserted into the shell and located with a peg. These new bushes were pre sized, much the same as big end shells, and fitted without line reaming/boring. The bearing material was a thin deposit.
They were described as a heavy duty bearing in the 1958 catalogues.
Same design bushes fitted to the A65 engines. Easier to assemble in the factory.
Some of the pattern bushes, both solid and composite supplied during the 1970s were quite poor quality, sometimes the oil holes in the bushes did not line up with the oil channel in the main bearing journal causing serious lubrication problems. Cannot comment on later repro bushes having been using the SRM conversion for the past 35 years.
Bulletin from December 1957 and catologue page from 1958 season.
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Just a quick reminder If you have the engine crankcases split now would be a good time to remove the spring and ball which is located behind that small screw next to the timing side bush this can only be done when the crankcases are split. It would be a good idea to replace them with new parts as they do help to control wet sumping but make sure you get the correct parts as when I did mine I was given the wrong spring at first. When you fit the ball give it a little tap to seat it before fitting the spring and screw.
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Thank you Julian.
I love how in the new features it has the "roll on center stand for minimum effort".
Yesterday I pulled a muscle in my back at minimum effort. *ex*
I am going to build a longer shallow ramp for in the shed, and just use the side stand elsewhere.
Lee
fixed it
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Lee,
I know you meant "center" stand, and I noticed the same thing.
Along with the other stuff, it was interesting that this list identifies '58 as the year of introduction for the "contoured" oil tank and tool box. Finally, did anyone know that, as of '58 (or ever), the fin edges were polished on alloy heads?
Richard L.
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I'm just going to say this out loud (so to speak) and give everyone a chance to chuckle under their collective breaths.
Now that I've initiated using the very local DIY makerspace machine shop, I am planning on boring my own timing side bush. Here's a link to see some of the machines. https://www.make-it-here.com/machining. I've watched the best Youtube videos on the subject and suppose I can do it with a trial run and fear only of destroying a perfectly good bushing.
Richard L.
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nothing ventured nothing gained Richard
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Go for it Richard. Just remember “measure twice, cut once”
Wish I had a workshop like that nearby... *wink2*
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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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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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Richard - make sure that the machineshop replaces that pic of the long-haired girl on the mill without any haircover.
regards
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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.
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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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I'm pleased to read about scraping the bush. I scraped the white metal big-ends on my Austin Seven.
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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
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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 .
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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.
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Slow maybe, but better than rushing into it and making a disaster. You're doing just fine.
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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.
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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.
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Corrected 3/4 of a thou, measured using a dial gauge bolted to the cases and a long bar applied to the other end.