The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: KiwiGF on 08.12. 2011 07:47

Title: Big end clearance and indium coating
Post by: KiwiGF on 08.12. 2011 07:47
I've searched the forum and I've not found a complete answer to some questions regarding big end clearances when getting a crank reground.

My small journal A10 crank is in for grinding down to -040 and the firm has asked what clearance I want and I want to be certain as I can be that I give the firm the right clearance to work to.

The questions......
1. Are the aftermarket shells all steel backed indium flashed lead bronze like the Munro book says they should be? (mine are MCA brand from Draganfly). It appears the indium "flashing" might be sacrificial for the running in period maybe?
2. Is the Munro book correct in saying the "new" clearance between journal and shell is effectively nil? (pg 117 where it also says 002 clearance due to wear results in knocking)
3. If the answer to (2) is yes does this apply even if the aftermarket shells are not indium coated?
4. Is the Haynes manual (pg 15) correct in stating the rod eye internal dia for a standard SJ journal is 1.4610 to 1.4615? (this implies a clearance of at least 001 which is not really nil like the Munro book says is correct)

Note BSA service sheet 207 does not give a clearance only the journal dia required to fit the shells of the various under sizes, -040 under is not stated as BSA only recommended down to -030 but one can safely assume the same clearances apply I think.

The journal size tolerance is given as the nominal under size minus 0005 - half a thou

Title: Re: Big end clearance and indium coating
Post by: MG on 08.12. 2011 11:05
Hello Kiwi,

A good topic, and one dear to my heart as you will soon see.

I'll be trying to answer your Qs one by one:

1) All the MCA (*gulp*) shells I have seen so far seem to be steel-backed aluminium-tin shells. NO lead bronze, NO running-in layer whatsoever (white metal, Indium, you name it, it's not going to be there). Aluminium shells are commonly used for low- and medium-load engines (petrol and non-supercharged Diesel engines) nowadays, but if you ask me, mainly for reasons of costs. I've been in contact with a very nice chap from Vandervell UK (now owned by Mahle), and he said W*$$*l asked them to produce proper m'cycle bearing shells for them, but then decided against it due to the high manufacturing costs! No more "made (with pride) in the UK" stuff for us...
If you want something good, get a set of shells from SRM, these are proper three-metal bearings (steel back, bronze, nickel barrier and a very thin running-in layer). SRM says they are made by Clevite in the US, a well known name in the world of engine bearings (now also owned by Mahle btw)!
2) Common sense ref bearing clearance is to use 1/1000 of the journal diameter. Anything between 1 to 2 thou will be just fine (I'm using 1.5 usually). 2 thou definitely won't result in knocking or premature wear, an engine with 2 thou bearing clearance and a working lubrication system will run happily for years. Another story is 2 thou of wear on the crank journal (out of round), resulting in a max. clearance of 4 thou and even more with worn shells. This IS going to knock! 2 thou out of round on the journal means it's time for a regrind.
3. Clearance figures apply to all sorts of shells.
4. yup.

The best way is to give them the rods and shells and have the crank ground accordingly to give correct clearance. Have them also check the blind bore on the big ends, rods are known to warp or wear ovally, which has to be fixed first!

Some pics for guidance:

This is an MCA (two-metal) shell, treated with a file. Note only one layer of aluminium-tin alloy and serial number for reference:

(http://img40.imageshack.us/img40/8388/alutinfiled.th.jpg) (http://imageshack.us/photo/my-images/40/alutinfiled.jpg/)

(http://img545.imageshack.us/img545/4333/alutinno.th.jpg) (http://imageshack.us/photo/my-images/545/alutinno.jpg/)


SRM shells:
 
(http://img6.imageshack.us/img6/2551/srmbox.th.jpg) (http://imageshack.us/photo/my-images/6/srmbox.jpg/)

(http://img855.imageshack.us/img855/4331/srmno1.th.jpg) (http://imageshack.us/photo/my-images/855/srmno1.jpg/)


Cheers, Markus
Title: Re: Big end clearance and indium coating
Post by: terryk on 08.12. 2011 11:32
Hi KiwiGF, You just get your crank ground to -040. The manufacturers of the bigend shells take clearance into consideration when they make them if they correctly made. When you assemble the conrods and tighten the bigend nuts to specified tention make sure they move freely with no up and down movement. Also make sure you use oil on the shells.  If when you assemble the rods there is not enough clearance and the rods bind then you can lenish the bigends a bit. if there is too much clearance then the bigend shell arent made to the correct clearance and they are badly made. But generally you just grind the crank to the undersize in stages of ten thou and assemble them. It should be fine.
The main journal can just be ground till it cleans up. You can make a bush to suit there is no need to grind to next undersize you can buy main bushes that need to be bored to size. The main bush needs to be line bored in line with the bearing housing of the drive side crankcase. Hope that helps and makes sense.
Title: Re: Big end clearance and indium coating
Post by: kommando on 08.12. 2011 12:54
The Clevite bearings shown above would be the closest to the proper VP2 Vandervell bearings, the overlay plating does not contain Indium which is an excellent anti sieze agent but that is only needed for running in, after running in its wear rate is greater than the nickle barrier so you pays your money and takes your choice on that one.

As an aside Vandervell licenced the Cast Bronze bearing production process off Clevite, Clevite is the company which delevoped the process not Vandervell. Vandervell added the Lead Indium plating as an alternative to the orginal Lead Tin plating.

However when you find NOS Vandervell bearings watch out as somehow instead of supplying cast bronze with a lead/Indium overlay for the A65 at least they supplied Whitemetal bearings, pattern parts are also around made from Whitemetal which should be avoided at all costs. I am sure this is at least partly to blame for the bad reputation of the A65. They also supplied Whitemetal to the B25 engine. Don't know if it was BSA or Vandervell who made that decision but I am sure it did not help in the relibility of big ends front.

In an engine such as an A10 or untuned A65 the Al/Sn bearings are perfectly adequate, I would only go for the Cu/pb with overlay plating for a tuned Spitfire engine or for racing.

More details in this thread, I will add a link back to this thread so the SRM Clevite bearings are known about.

http://b50.org/phpBB2/viewtopic.php?f=3&t=4158
Title: Re: Big end clearance and indium coating
Post by: MG on 08.12. 2011 12:59
Thanks kommando, I shall be having a look at the link you posted in a minute.

Ref Al/Sn bearings, yes, okay for a standard engine or a mildly tuned one, I agree, but if I can get something much better for 15-20quid more, it's a no-brainer, especially if the alternative supplied by M**, W****, etc. is of unknown origin and technology!
SRM have bothered to invest into the best technology available to supply decent parts, and that should be honoured by our purchase.
Just my 2p worth though.

Cheers, Markus
Title: Re: Big end clearance and indium coating
Post by: kommando on 08.12. 2011 13:19
VP2 is the best bearing from the era but overkill for a cooking engine, my 850 commando will be getting Al/Sn bearing if it ever needs rebuilding despite me having access to set of VP2 bearings for it. Commando original bearings are Al/Sn.

If a bearing company today was presented with a tuned A65 engine they would specify the crank be made from a nodular grade of steel and the bearing would be an Al/Sn bearing with a 1% Cu addition and some silicon, this bearing/crank combination conditions the crank as it runs. Thats is the current std for hot petrol engined cars with a lot more output per L than an A65 with an expected life of 100K miles plus. And also with Al/Sn main bearings with the oil being fed to the big ends through grooved mains just like an A10/A65.

Thats when you are making 1000's a week, for a rebuild then for piece of mind the Clevite is an option worth considering but don't worry if Al/Sn is used.

Avoid Whitemetal !!
Title: Re: Big end clearance and indium coating
Post by: RichardL on 08.12. 2011 14:17
Terry,

What the heck (I really mean "hell" here, and but that would be impolite) is "lenish"? Google isn't helping with the definition . If it means honing out the ID of the rod journals, that was a mistake that cost one machinist working on my bike a set of MAP billet rods to atone for his sins. The same machinist ground the crank close to the bottom of the tolerance, so I like Markus' point of having the crank ground to fit the shells.

Richard L.
Title: Re: Big end clearance and indium coating
Post by: kommando on 08.12. 2011 14:28
Guessing Lenish is Linish which is http://en.wikipedia.org/wiki/Linishing
Title: Re: Big end clearance and indium coating
Post by: RichardL on 08.12. 2011 22:01
Thank you, Kommando.
Title: Re: Big end clearance and indium coating
Post by: terryk on 09.12. 2011 12:05
Ha yes linish but not the rods the journal. Just take a small amount off with emery strips by hand not with a machine. I have done crank grinding and when we finished grinding a crank we always gave it a light linish with emery strips.
By all means take your crank, rods, and B/E shells to a machine shops and get them to do it. I always just got the crank ground to undersize and fitted it all myself. I havent had too much trouble but with some cars I have found variations in B/E shells between different manufacturers but it was ok in most cases.
Title: Re: Big end clearance and indium coating
Post by: chaterlea25 on 09.12. 2011 12:34
Hi All,
All this conversation re different shell bearing materials had me running out to the "shed" to check
what kind of B/E shells had been supplied by SRM for the current engine project??
Relief in that they are the USA made ones, mentioned. *smiley4*
Reading through the B50 link pages and Kommando and MG's posts, I have learned a lot !!!
All that glitters and all that  *eek*  ???? ????

Going back to Kiwis original questions, The sizes I supply to my machine shop are the original crank size minus the undersize. that said they have all the old books for references anyway

A BIG MUST WHEN HAVING THE CRANK GROUND IS TO HAVE THE CORRECT RADAII between journal and webs

I have seen BSA and other cranks snap like twigs when this has been neglected  *eek* *eek* *eek* *eek*

I am waiting for a friend to bring a pair of MAP rods for this engine from the USA before I continue with the build
I baulked at the price of SRM or Lightning rods  *sad2*
The MAP rods come in at near enough the same number of $US versus £ sterling   ???? ???? ????

That said I am really happy with all the work that SRM did,
The crank was found to have been worn and punch marked where the main roller bearing fits  *sad2* along with the usual worn splines etc.
Its all ready to rock and roll now  *ex* *ex* *smile*

Cheers
John O R




Title: Re: Big end clearance and indium coating
Post by: KiwiGF on 09.12. 2011 13:01
Thanks Very much guys...like most times a good set of experiences and I've decided to keep the Mca brand shells and ask for 001 clearance ...fingers crossed that works out and if doesn't I'll report back here.....

The rods I'm using are billet lightning rods from from thunder engineering uk cost 175gbp correction 250gbp not 175gbp! (senior moment) plus freight which I thought a good price they look identical to MAP / SRM rods
Title: Re: Big end clearance and indium coating
Post by: kommando on 09.12. 2011 17:06
I checked the photo of the stamping symbols on the MCA bearings, they identify the manufacturer as Glacier bearings in Kilmarnock and are AS15 Al/Sn bearings. They are of the same type as the bearings used on Norton Commando's.

They are not as strong as VP2 bronze bearings, but that will not matter in a non racing engine, but also as they do not have a soft overlay which picks up grit and reduces the wear on the crank journal you do need to use them with a filter in the return oil pipe. If you look at the photo of the used MCA bearing you will see lines in the bearing surface, these are from grit particles running in the oil layer between the bearing and the journal hence the need for a filter. On the plus side the Al/Sn bearing itself will have less wear from contact with the journal as it does not have the soft overlay. On a Bronze bearing the overlay acts as a trap for grit and to stop acids in the oil from attacking the bronze so once it goes the bronze will deteriorate rapidly. Al/Sn bearings are not attacked by the acids so no need for a plating layer.
Title: Re: Big end clearance and indium coating
Post by: MG on 09.12. 2011 17:13
Yep, the shell came from an engine that had done good mileage without an oil filter fitted.
I don't think acidic residues will be a huge problem in any of my engines, with yearly oil changes, done before the winter break with a short run to have all engine internals covered with fresh oil.
Title: Re: Big end clearance and indium coating
Post by: chaterlea25 on 09.12. 2011 20:53
Hi ALL,
Kiwi,
Here is the mail I recieved from Thunder Eng,
I know that there would be no VAT on exporting to New Zealand But it is considerably more than £175 ???

""Thank you for the conrod enquiry, the BSA A10 large journal rods are
availiable from stock priced at £250.00 per set delivery is £15.50 plus VAT
total £318.60
To place an order please call on ++44 (0)116 2834640.
If you require any more info please let me know""

SRM's price is £280 +post+VAT per pair

MAP rods are US$ 360 per pair  ( I did not have to pay tax as they were being shipped out of state)

HTH
John O R
Title: Re: Big end clearance and indium coating
Post by: KiwiGF on 09.12. 2011 22:53
John I have corrected my earlier post the price I paid for rods was 250gbp plus freight zero VAT
Title: Re: Big end clearance and indium coating
Post by: MG on 10.12. 2011 08:29
FYI, a comparison of different bearing technologies wrt to load capability, from German literature, bearing types from left to right are:
white metal - two-metal - three-metal Pb-based - three-metal Sn-based - groove-type (Miba system) - Synthec - sputtered - lead-free sputtered w/ running-in layer

Thought you might find this interesting.

Cheers, Markus
Title: Re: Big end clearance and indium coating
Post by: bonny on 16.12. 2011 18:16
Thanks Very much guys...like most times a good set of experiences and I've decided to keep the Mca brand shells and ask for 001 clearance ...fingers crossed that works out and if doesn't I'll report back here.....

The rods I'm using are billet lightning rods from from thunder engineering uk cost 175gbp correction 250gbp not 175gbp! (senior moment) plus freight which I thought a good price they look identical to MAP / SRM rods

The thunder engineering rods are reputed to be very good and are recommended by people like dave nourish of nourish race engines for his engines , i gave up on map as anytime i contacted them for the rods i wanted , they told me to get back to them in a few weeks , this went on endlessly.
Title: Re: Big end clearance and indium coating
Post by: KiwiGF on 16.12. 2011 21:10
I might be spicing things up a bit here.....but as regards softer shells not wearing the crank journals as much I've always thought that in general (and only when lube is present) it's the softer part of a plain bearing that wears the least as harder metal particles - including particals from the other, harder part of the bearing- embed themselves in the surface of the softer part, effectively reducing wear of the softer part to a fraction of that which occurs on the harder part.

If lube is NOT present in enough quantity then the softer part will suffer high wear.

I get my reground crank back today and will be able to see if the Mca shells have glacier markings, the eng company said they were definitely not white metal though.
Title: Re: Big end clearance and indium coating
Post by: MG on 16.12. 2011 21:20
Embedded particles can have a lapping effect on the crank journal, mainly an issue when running without an oil filter I would think.
Title: Re: Big end clearance and indium coating
Post by: kommando on 20.12. 2011 17:13
Initially the soft layer is thick enough to absorb the hard particles and deep enough not to wear the journals, once the soft layer wears then the particles are re-exposed and then they wear the journal. Hence for a roadbike the harder surfaced Al/Sn bearings with a good filter are better than the VP2 bearings as the Al/Sn does not have the soft layer to wear away so it maintains size for longer and the filter takes care of the particles. VP2 in a race bike that is rebuilt yearly with new shells never has these problems and can even but run without a filter as the soft layer is renewed annually.