Author Topic: A10 Timing side main bush/bearing  (Read 9299 times)

Online RichardL

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Re: A10 Timing side main bush/bearing
« Reply #15 on: 02.08. 2008 06:05 »
Brian,

I happen to own an amazing set of books on metalurgy that I rarely look at. Thanks for suggesting the research on this. It will be a great excuse to get some use of those books, once I am home from vacation next week.

I think I am a bit confused on the whole idea of one type of bronze wearing the crank more than another. After all, the point is for the crank to ride on film of oil that is 0.0005"-0.001" thick, not to be in contact with the bronze. Perhaps the concern is for which material causes the worst damage if the bush is starved of oil. Or, perhaps, the concern is for when the oil carries abrasive particles. Then, the particles will grind away at the crank as well as the bush and it would seem the harder bush material would be better.

I will be interested to hear the ideas and, perhaps, warnings and admonishments of the many here with deep experience (in motorcycles, I already have expereince in the other).

Richard

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Online Brian

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Re: A10 Timing side main bush/bearing
« Reply #16 on: 02.08. 2008 07:37 »
Richard,
I thought I would be smart and look up on the internet all about bronze, but all that did was confuse me even more. By what I can see basic bronze is copper and tin but what I didnt realise was that there are so many other bronze alloys. I think I did answer one of my own questions however, I said before that some bronzes seem harder than others. Apparently when you add phosphorus to make what we all know as phosphor bronze it becomes very brittle which would explain the symptons I have come across when machining some of it.
What we really need to know is which bronze alloy is best suited to what we are doing eg. bronze to steel in a high temperature wear situation. And just how you identify the different bronze alloys.
One thing the articles I read did all seem to agree on is that none of the bronze alloys should wear out steel faster than themselves, if thats correct then the bush in a engine should always outlast the crank, but the cranks definitely wear.
Like I said, I think I am more confused than before.
Forget the vacation, get home and read those books !!!!!
Brian.
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Online groily

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Re: A10 Timing side main bush/bearing
« Reply #17 on: 02.08. 2008 14:15 »
Gents, for what it's worth I thought I'd ask someone who'd recently made some for a Square 4 (similar thing to a BSA on each crank) what he used. He (consultant mechanical engineer and well-versed in these things) told me (from memory) he used leaded gunmetal tin bronze, SAE660, about 7% tin and also 7% lead for seizure resistance. Made it to give 1 thou clearance fitted, and paid total attention to concentricity, roundness and line reaming. His view is that the fit is the number one point, and that if it's good there will be little chance of contact between journal and bush. Slipperiness of material is pretty important he tells me as 'obviously there is no hydro-dynamic lubrication at cranking speeds'. Er, 'obviously'.
As an old-time A65 person, he also said his memory was that in the old days when the bikes were still current the solid bushes were preferred over the lined ones. My memory is similar, with no empirically-backed reasons to support. Maybe it was him that said it when we were all drunken students together!
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Bill

Offline beezalex

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Re: A10 Timing side main bush/bearing
« Reply #18 on: 05.08. 2008 14:11 »
My understanding is that the reason for more wear with the harder phosphor bronze is that contaminants in the oil which would normally become embedded in a softer material (like the original lead/tin babbit) now become abrasive.  It surprises me that noone here mentions whether or not they have used a return-line filter...makes me think they haven't.
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Alex

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G/F DAVE

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Re: A10 Timing side main bush/bearing
« Reply #19 on: 05.08. 2008 19:41 »
Hi, Beezalex I have always used a inline cartridge type filter on the return (wouldn,t run without it) also a magnetic sump bung that is free from swarf/particles when oil change time comes, every 1500 miles. As for T/S bush it,s up to everyone to make their choices on what type to use & availability. I choose a ALPHA L/B due to bad experiances with P/B type, BSA got it right with this type of bush & the only reason for a one piece P/B type is its easier & cheaper manufacture. G/F DAVE
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Offline terryk

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Re: A10 Timing side main bush/bearing
« Reply #20 on: 18.01. 2009 12:44 »
Hi all I have found a fella that makes cast lead bronze timing bushes. Here is the email he sent back to me when I questioned him about possible crank wear etc from the timing bushes on the market at present.
He is ok with me posting his email details and is happy to take orders.

His email is mike_jan@dsl.pipex.com
 

Hi Terry,
           I have been making bushes for the Ariel for a while and have had no reports of excessive crank wear, the A10 bushes I have been making for about 6 months and have not received any adverse comments.I haven't been making them long enough to receive long term feedback but I have made them to be superior to the original 2 piece white metal ones. Having the lead component increases wear resistance on both the shaft and bush and being a solid one piece construction they run cooler as there is no thermal barrier as the originals have white metal on to bronze then on to steel, being solid the heat passes straight into the cases with no barrier. That's the theory anyway, time will tell.
          My day job is bike restoration and repairs and started making the bushes as the pattern ones available were poor quality, I'm afraid I don't supply any other parts just bushes which I can make to pattern or drawing, the bushes can be made to any size you require therefore the shaft does not have to be ground by 10thou. min. just cleaned up and the correct size bush made to suit making the shaft last longer.
           I hope this helps a bit.
              Regards   Mike.
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1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
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Offline A10Boy

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Re: A10 Timing side main bush/bearing
« Reply #21 on: 18.01. 2009 13:19 »
Terry

Thanks, that is very useful info.
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Andy

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Offline olev

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Re: A10 Timing side main bush/bearing
« Reply #22 on: 20.01. 2009 10:44 »
Thanks TerryK,
Your post is prophetic as I've just started looking for a timing side bush for the a7.
I know you were looking a while back. Did you get one off Mike?
Where is he, America?

On another related subject,
If this bush needs to be line bored then the crank would need to be very straight.
Do these cranks ever bend and what tolerence is allowable.
cheers
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Online RichardL

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Re: A10 Timing side main bush/bearing
« Reply #23 on: 20.01. 2009 12:28 »
Regarding a bent crankshaft, it would seem that any out-of-parallel amongst the bearing surfaces would be corrected during grinding. However, assuming a new bush without a new grind, I would say that 0.0005 should be used as the maximum out of parallel. This is based on the allowed timimg bush bearing tolerance of 0.001"-0.002".

No doubt (or, definately) there are those that can answer this from their specific experience, but I think this is a reasonable engineering answer.

Richard L.
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Offline terryk

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Re: A10 Timing side main bush/bearing
« Reply #24 on: 20.01. 2009 14:07 »
The beauty of getting a bush made is it can be any (inside dia) size you like. You dont have to grind your crank in steps of ten thousands as you would if you use the ones on the market. This makes your crank last  a lot longer.
Firstly you need to check your bigend pins to see if they are out of round or scored etc and need grinding as well. Then get all grinding done at one time.
With bigends you have to stick to available bigend shell sizes in steps of ten thou.
With the timing side of crank get it ground just so its true (round ) with no scores etc. You will need to show the machinist the BSA service sheet that says radius, I cant remember what number it is I will have a look. Then you can order a bush with smaller (inside dia) than the (outside dia) of crank.
Note the (inside dia) of the bush may decrease a bit on installing to the crankcase. The new bush after installed to the crankcase needs to be line bored true to the other side crank case (drive side) bearing housing. Otherwise it can wear the bush out prematurely.
I haven't ordered a bush from Mike yet. I'm checking my cranks etc first but I will get some.
He is in Cornwall UK. He has them on ebay starting price 38 pound which is a bit dear but I guess time is money. You would be better to contact him by his email.
Hope this helps.
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1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline A10Boy

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Re: A10 Timing side main bush/bearing
« Reply #25 on: 26.05. 2009 21:18 »
Terry

How did you get on with this, do you have an update ?

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Andy

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Offline terryk

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Re: A10 Timing side main bush/bearing
« Reply #26 on: 28.05. 2009 15:04 »
No haven't got onto that main bush yet, I have been side tracked lately with keeping my single BSA on the road and collecting parts for a 1948 A7.
I will probably machine my own main bush out of lead bronze and line bore it myself. I hope to build a twin motor in the next few months so I will keep you posted.
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1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline MikeN

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Re: A10 Timing side main bush/bearing
« Reply #27 on: 28.05. 2009 22:25 »
As has been stated, With good lubrication , little metal to metal contact should occur so wear should be minimal.
   However if you have a hard shaft running in a SOFT plain bearing and you introduce an abrasive ( dirty contaminated oil with abrasive particles in suspension for example) ,what you have then is a lap.
 Lapping can be used to reduce the diameter of a hardened shaft or enlarge a hardened bore,correct out of roundness or finish a hard flat surface truly plain.
 Lapping is carried out by using a material softer than the work and charging it with abrasive.this becomes embedded in the soft material and it will most definately wear the harder material faster than the soft lap.
  Laps are ideally made from lead or copper but other materials that can be used  are iron , aluminium and bronze.
  I once got to look inside a 500cc unit engined Triumph that had done about 2000 miles after a full engine renovation and had been rebuilt with (I assume ) shot-blasting grit or some such abrasive left in the oil tank after stove enameling.
  The knocking from the engine meant the owner had to take it apart again.
   The steel of the timing side main journal on the crank had worn over .020" oval but there was very little metal missing from the bronze bush. Similar story with the inlet (but not the exhaust for some reason)camshaft.
    The big ends were untouched which (I believe) shows the efficiency of the sludge trap.I am sure that if the debris had got into the white metal shells it would have rapidly worn away the crankshaft big end journals in a similar fashion.
 Now then, As none of you reading this is ever likely to neglect an oil change or have any abrasive particles in your engines I feel confident that none of the above will ever befall you.
  I suspect that the hardness or softness of the bronze used is not as important as a good oil pressure and clean oil.
Mike.
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Offline terryk

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Re: A10 Timing side main bush/bearing
« Reply #28 on: 30.05. 2009 11:45 »
Good point Mike.
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1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline Bsa Nut

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Re: A10 Timing side main bush/bearing
« Reply #29 on: 03.11. 2013 07:58 »
Can anyone recommend a USA based, reputable shop for handling the time side bush? I would love to send my next one over to SRM, but roller conversion is just too costly. I would let them handle the bush replacement, but if someone in the states can do it, perhaps shipping would be easier/less costly.
On my A65, I ended up doing it myself, because everyone was either too expensive, too backed up, or never returned my calls.
;(
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