The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: terryk on 29.07. 2008 13:19

Title: A10 Timing side main bush/bearing
Post by: terryk on 29.07. 2008 13:19
Hi all, I've heard it mentioned on this site that the bronze timing side main bush wears the crankshaft main journal and the lead bronze two part ones are the ones to get. What does everyone think? Where can you get the NOS ones. Thanks in advance for comments.
Title: Re: A10 Timing side main bush/bearing
Post by: RichardL on 29.07. 2008 16:18
If I recall correctly, I asked this same question of SRM and was told that the solid bushes were the only ones they sold. I took this to mean they had great faith in them.  Do give them a call to ask confirm this point.

Richard
Title: Re: A10 Timing side main bush/bearing
Post by: RichardL on 29.07. 2008 16:31
Adding to my previous post, I note that the point regarding solid phosher bronze wearing the crank, versus 2-piece lead branze was made by a member of this Forum who's opinions I greatly respect. So, I redouble my suggestion to check this out for yourself with SRM, read the posts at http://www.a7a10.net/forum/index.php?topic=485.0 (which, I think, you already did), and contact the member directly who gave the advice (G/F Dave).

Richard
Title: Re: A10 Timing side main bush/bearing
Post by: G/F DAVE on 29.07. 2008 22:04
Re; Timing side bush I have had problems in the past using PB1 phoshur bronze bush.The ones I had fitted came from SRM within 15000mls I had the familiar rumblings thru footrests. The crank was worn oval so had to be ground from -020 to -040. Another 12000 mls  then the rumblings were back. Needless to say -040 is the last grind so time for another crank. I was lucky to find a big bearing super rocket crank on STD which I had ground to -010 timing side & big end journals, the guy who did the work had new old stock alpha lead/bronze bushes & glacier big end shells.These were fitted 23000 mls ago and the engine is still smooth and nearly vibe free.The lead bronze bush is the type fitted from the BSA  factory, but be aware there are cheap nasty pattern ones about that are not pegged but glued and may turn inside steel housing shutting off oil supply to big ends. If you can find original BSA or ALPHA you are going to be very lucky but I have seen them on EBAY site from time to time. These are my experiances with PB1 bushes yours may be different . I do give my goldflash some stick as with all my old bikes also regular oil changes & more important a inline oil filter are essential. G/F DAVE....
Title: Re: A10 Timing side main bush/bearing
Post by: trevinoz on 30.07. 2008 00:20
I made an insert for the original bush from LG1, which is leaded gunmetal. It is in my '55 Flash and so far so good, only a few thousand miles so far. I previously had a bush made from Aluminium Bronze fitted to my RGS and it wore the journal badly as noted above with PB1.
                                 Trev.
Title: Re: A10 Timing side main bush/bearing
Post by: Brian on 30.07. 2008 02:01
Ive been watching this subject for some time now with interest. My plunger A10 is still running on the original BSA bush and has done who knows how many miles, thousands. I have recently rebuilt my 61' A10 and after discussion with SRM fitted a solid bush, I will know in the next twelve months or so if this is good or bad. One thing we all say on the forum is that how important it is to have a replacement bush line reamed or bored to the opposing case to be absolutely sure it is in line. The original BSA workshop didnt do this, they had a reaming plate that fixed to the outer timing side and acted as a guide to ream the bush. I have added a scan from the original manual showing this. Apparently they trusted the accuracy of their maching of the cases, interesting.       Brian.
Title: Re: A10 Timing side main bush/bearing
Post by: groily on 30.07. 2008 15:56
'tis very interesting Brian. Wonder how they machined the the case to get such accuracy (if they did indeed). Or maybe they were just happy to get the timing side bush reamed square with the case? Or  - maybe they had a mandrel attachment to the reamer which was supported in the drive side inner race . . . ?(which is what I'd have expected seeing the trouble they went to to make the guide plate in the first place!)
When at some point I have to do my A10's bottom end, which I'm sure is only a matter of time, I'll come back to this!
Title: Re: A10 Timing side main bush/bearing
Post by: Brian on 31.07. 2008 01:24
I found this interesting too when I came across this picture and part in the manual. They dont mention any sort of guide or mandrel but it is hard to imagine not using one. I guess that when this was written it was all new stuff so maybe they thought their machining was good enough. The plate also has a hole in it to ream the camshaft and idler pinion bushes and thay would be difficult to put any sort of guide behind. Who know's ? I have some video footage taken in the BSA factory I think in 1962 or early 63' and it shows them assembling a A10 engine but unfortunately doesnt show that part of the operation. It does show them doing some things like drilling and tapping holes in crankcases for barrel studs etc and they just rely on the accuracy of their machines to get everything square. I always line ream the main bush and would not recommend otherwise but just thought this was interesting.
Title: Re: A10 Timing side main bush/bearing
Post by: GuyboA10 on 31.07. 2008 04:15
G'day Brian & co. In regards to this matter i came across a photo and description of a reaming tool that entered the left side case and protruded through to the timing side for acurate reaming of the T-side bush. The cases were bolted together and the tool was guided by the drive side bearing. This to me seems like the only way it should be done. As a novice brit bike builder, who has learned alot, i cant see any other way that would be as accurate. maybe on a very expensive machine, but for the average brit bike builder on a limited budget, the reaming tool seems to be the most effective solution.
i will try and find the photo. Also i think it was demonstrated on an A65, but i'm sure it would work on an A7/10. I think the guys name was Mark Parker, an Aussie Nsw? don't quote me on that. ( apologies to M Parker if i am mistaken)
cheers Guy.
Title: Re: A10 Timing side main bush/bearing
Post by: terryk on 31.07. 2008 09:43
There must be someone who can make lead bronze timing bushes like the Alpha ones to put our minds at ease. Has anyone used the SRM bronze ones for a long time with success also making sure it's line bored properly and pulled the engine apart for some other reason and seen that there is not a lot of wear on the crank from them?  If so we have nothing to worry about but I don't like the idea of wearing the crank out in a hurry they are getting too had to find and too expensive. Beside I dont want to be pulling the engine apart because of unreliable parts demaging had to find good parts. I want to put lots of miles on my bike not lots of hours working on it and looking for other cranks. Terry in Australia
Title: Re: A10 Timing side main bush/bearing
Post by: octane on 31.07. 2008 09:54
G'day Brian & co. In regards to this matter i came across a photo and description of a reaming tool that entered the left side case and protruded through to the timing side for acurate reaming of the T-side bush. The cases were bolted together and the tool was guided by the drive side bearing. This to me seems like the only way it should be done. As a novice brit bike builder, who has learned alot, i cant see any other way that would be as accurate. maybe on a very expensive machine, but for the average brit bike builder on a limited budget, the reaming tool seems to be the most effective solution.
i will try and find the photo. Also i think it was demonstrated on an A65, but i'm sure it would work on an A7/10. I think the guys name was Mark Parker, an Aussie Nsw? don't quote me on that. ( apologies to M Parker if i am mistaken)
cheers Guy.

Hi Guy

It's here: CLICK (http://www.britbike.com/ubb/cgi-bin/ultimatebb.cgi?/ubb/get_topic/f/10/t/007559/p/1.html)

...scroll down a bit.
Title: Re: A10 Timing side main bush/bearing
Post by: RichardL on 31.07. 2008 15:35
Gents,

I couldn't resist borrowing this post from the BritBikeForum. I don't believe there are any copyright issues to be concerned with, however, as always, I rely on our administrator to make the determination.

Richard





Ok here are some pictures of the ream;

The piece with the cone screws onto the handle of the ream and the cone slides up and down and the ream turns inside it. This ream is 1.5" and bigger but seems to adj down a little from that. A smaller ream would have a smaller cone and need perhaps something made to fit into the D/Side case. As it is this larger cone fits tightly into the old oil seal, for those who think that may be too imprecise something could be made, however the seal seems to work fine and that end of the ream stays well held.

The ream adjusts by the two collars that can be turned to move the blades along the slots in the shaft that are tapered.

The ream makes for a very square hole, and the process would be made much simpler with inside and outside mics, so you could slowly approach correct size. You can guess clearence probably quite good if you remove the oil pump studs and test the crank from the outside and slowly creep it up. The ream can be removed and re-inserted without unbolting the cases. Once the crank drops in, and is only in the bush, the amount it rocks will indicate clearance. The one I did some years ago hardly rocked, but when in the motor, in both bearings, it would spin very freely, indicating good alignment.
Title: Re: A10 Timing side main bush/bearing
Post by: RichardL on 31.07. 2008 16:25
... I don't like the idea of wearing the crank out in a hurry they are getting too had to find and too expensive.

Until just recently, I always considered crank grinds in 0.010"increments because of the available sizes of rod bearings. Then, I woke up to the fact that the timing-side bushes do not need to follow the same logic. One need only take off as much from the crank as necessary to clean up, then ream the new bushing accordingly (or vice-versa, perhaps). This could afford more main journal grinds if one does not need to do the rod journals or if there are more steps left in the rod journal life.

Of course, this is old news to some, but may be helpful to others with my brand of sleeping sickness.

Richard
Title: Re: A10 Timing side main bush/bearing
Post by: Brian on 01.08. 2008 08:28
That was the very reason I went for a solid bush, thinking that when it wore I would get the crank ground just enough to clean it up and then make a new bush to suit. By what I understand from this thread the solid bush seems to cause the crank to wear so that being the case the bronze used must be too hard. So I wonder is it possible to get a softer bronze. I do know that bronze varies in hardness, I have been buying bronze bar for years to make bushes etc out of and have learnt that you can get some idea of how hard it is by its colour. The lighter [or whiter] it is, the harder and the yellower it is the softer. I have queried this with my supplier but they only know it is bronze bar and have no idea about its properties. Do we have a metalurgist amongst us ?
Title: Re: A10 Timing side main bush/bearing
Post by: GuyboA10 on 02.08. 2008 04:39
hi, yep , thats the one! cheers to octane & manosound. i thought i'd seen it on britbike.com.
Has anyone here used that tool? on their a7/10's?
cheers, Guybo.
Title: Re: A10 Timing side main bush/bearing
Post by: RichardL 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

Title: Re: A10 Timing side main bush/bearing
Post by: Brian 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.
Title: Re: A10 Timing side main bush/bearing
Post by: groily 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!
Title: Re: A10 Timing side main bush/bearing
Post by: beezalex 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.
Title: Re: A10 Timing side main bush/bearing
Post by: G/F DAVE 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
Title: Re: A10 Timing side main bush/bearing
Post by: terryk 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.
Title: Re: A10 Timing side main bush/bearing
Post by: A10Boy on 18.01. 2009 13:19
Terry

Thanks, that is very useful info.
Title: Re: A10 Timing side main bush/bearing
Post by: olev 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
Title: Re: A10 Timing side main bush/bearing
Post by: RichardL 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.
Title: Re: A10 Timing side main bush/bearing
Post by: terryk 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.
Title: Re: A10 Timing side main bush/bearing
Post by: A10Boy on 26.05. 2009 21:18
Terry

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

Title: Re: A10 Timing side main bush/bearing
Post by: terryk 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.
Title: Re: A10 Timing side main bush/bearing
Post by: MikeN 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.
Title: Re: A10 Timing side main bush/bearing
Post by: terryk on 30.05. 2009 11:45
Good point Mike.
Title: Re: A10 Timing side main bush/bearing
Post by: Bsa Nut 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.
;(
Title: Re: A10 Timing side main bush/bearing
Post by: cyclobutch on 04.11. 2013 12:48
Hmmmm. So points of note then:

I thought that the softer material always wore the hard one? My understanding being that any contaminants stick in the soft stuff and then wear the hard stuff. So to some extent a harder material bush should be better?
(My sister has proven this with different grade gold in her engagement and wedding rings).

The whole point of 'white' metal bearings is that there is no direct metal to metal contact. The important aspects here being good oil pressure and clean oil.

Except, as noted, when we're kicking over with near zero oil pressure. So an easier starting bike should give better engine life?

I'm running a return side filter and magnetic sump plug, and change oil fairly regularly. I've no clue what my bush is made of - though it's only done around 2.5k miles since it all went together ... some 3 or 4 years ago. At 53, though not necessarily expecting to make old bones, at that level of usage I wasn't really expecting to split the cases again.

Title: Re: A10 Timing side main bush/bearing
Post by: RichardL on 04.11. 2013 15:35
Luke,

It seems you and I are on parallel tracks with the work on our A7s. I am also in the midst of trying to un-sieze my pistons and, before long, will need my timing-side bush replaced.

I thought I had previously asked  where you're located, but it seems not. I am in the western suburbs of Chicago and a local automotive machine shop (Custom Engine Service, Aurora, IL, ph: (630) 844-1071) has worked out very well for me.

C.E.S. just did the timing-side bush on my A10. I explained what I wanted, provided the new bush and left him the Haynes manual (doubt that he needed it). As far as I'm concerned they did a top-notch job. He says it's 0.001" clear and I believe it. I told him I thought that the journal needed to be ground, but I was wrong and he told me all it needed was polishing out the high spots of some scratches, thus, foregoing the money.  Sooo much better than the last time it was done by a Brit bike specialty shop whom I don't name in open forum (PM me if you want that story).

Now, don't expect to get a receptionist answering the phone, these folks are all shop and no frills except for, apparently, having every kind of machine needed to work on internal combustion engines and wicked skills. (Crank and cam grinding; welded journal buildup, spray metalizing, magnafluxing, balancing, line boring, etc, etc, etc.) Oh, did I mention the price, in my opinion, was quite reasonable? No, I don't own the place or have any relatives working there, but I hope they remain in business as long as I am still working on engines.

Richard L.
Title: Re: A10 Timing side main bush/bearing
Post by: Bsa Nut on 05.11. 2013 03:13
Hi all, I've heard it mentioned on this site that the bronze timing side main bush wears the crankshaft main journal and the lead bronze two part ones are the ones to get. What does everyone think? Where can you get the NOS ones. Thanks in advance for comments.

I've gotten OEM BSA bushes from Baxter cycles in Iowa...they may have a few more on the shelf. ;)
Title: Re: A10 Timing side main bush/bearing
Post by: bsa-bill on 05.11. 2013 11:12
Only fitted two both supplied by the Brothers Brum (C&D Autos) solid PB I think and being one size can be machined to fit the crank so as been said already the crank does not need to be taken down in ten thou steps.
So I've limited experience but no bad experience, only thing of note I've heard is the two part ones can separate (peg shears) resulting in one part moves within the other and the oil holes get out of sync -- not good.
Also should mention I've no connection with C&D Autos other than always receiving good stuff and advice, and the stuff usually is with me next day