The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Greybeard on 09.12. 2015 19:01

Title: Am I going to regret not buying this crank?
Post by: Greybeard on 09.12. 2015 19:01
Stated as a standard crank
http://goo.gl/Bh93Pz
Title: Re: Am I going to regret not buying this crank?
Post by: RichardL on 09.12. 2015 19:59
It is a chunk of change but, then again, it has two or three grinds left on it. I suppose it depends on how bad you need it. MB-Transits is a member here, maybe he would consider a member discount.

Richard L.
Title: Re: Am I going to regret not buying this crank?
Post by: Greybeard on 09.12. 2015 20:21
I don't need it at the moment but you can bet your life that when/if I do need one they will be double the price!
Title: Re: Am I going to regret not buying this crank?
Post by: Rocket Racer on 09.12. 2015 20:35
Personally I'd only be looking for a crank if I was worried about how worn my engine was and also knew it was already well undersize. Or it was apart and I knew it was beyond redemption
A std crank would be nice but is your existing crank that bad it will need replacement next time the motor comes down?
That's a lot of money for something you might not ever need.
Title: Re: Am I going to regret not buying this crank?
Post by: Greybeard on 09.12. 2015 20:52
Don't worry, I'm not buying it.  *smile*
Title: Re: Am I going to regret not buying this crank?
Post by: RichardL on 09.12. 2015 21:29
In the case of my machine shop, I thoroughly believe them whey they say they can build-up with a high-quality weld when (no "if" while I can ride) I need it. So, short of breaking it in half, I, too, must pass on it.

Richard L.
Title: Re: Am I going to regret not buying this crank?
Post by: TT John on 10.12. 2015 10:05
I had to replace a crank just after I did a rebuild on my 57 Golden Flash but I had my old one rebuilt up with weld and then ground to the original size, they did a fantastic job but it cost me £300, that is a small journal one, which is now waiting in stock, hopefully I won't need it but you never know. *wink2*
Title: Re: Am I going to regret not buying this crank?
Post by: nimrod650 on 11.12. 2015 18:55
regarding building up with weld dont they metal spray anymore
Title: Re: Am I going to regret not buying this crank?
Post by: morris on 11.12. 2015 20:20
regarding building up with weld dont they metal spray anymore

Basically talking about the same thing here because "metal spray" can be regarded as a form of welding:
https://en.wikipedia.org/wiki/Thermal_spraying
Title: Re: Am I going to regret not buying this crank?
Post by: jachenbach on 12.12. 2015 00:00
Seems awfully expensive to me. I sold 2 or 3 spares last winter and don't think I got more than $250 US for any of them. And I thought that was a lot.
Title: Re: Am I going to regret not buying this crank?
Post by: mikeb on 12.12. 2015 03:07
if you look at the second pic (of the timing side end) or the first pic and zoom in... looks like the shells are in place protecting the  main journals but those journals don't appear to have much of a radius. i'm no expert but if that's true it's likely been metal sprayed already....?  *eek* I think I'd want to view a better photo for that $$$
Title: Re: Am I going to regret not buying this crank?
Post by: coater87 on 12.12. 2015 14:53
if you look at the second pic (of the timing side end) or the first pic and zoom in... looks like the shells are in place protecting the  main journals but those journals don't appear to have much of a radius. i'm no expert but if that's true it's likely been metal sprayed already....?  *eek* I think I'd want to view a better photo for that $$$

 If you look even closer, it looks like there might be some inclusions in the same picture. If that crank was here in the states, I would say we are nuts and thats at standard. Being its across the pond, I am going with more than likely a built-up crank.

 You guys over their were much more prolific at rebuilding and keeping vehicles. Over here people just seemed to buy new or trade up. Once it needed a complete rebuild, it was parked or junked.
Title: Re: Am I going to regret not buying this crank?
Post by: RichardL on 12.12. 2015 15:56
Well guys, as I said, MB Transits is a member here, so you could try sending a PM (or a question through eBay) if you are interested. For my way of thinking, and for that money, I go by the old saying: "better the devil you know than the devil you don't know," which would lead me to a genuine weld-up and regrind. i don't know how much that would actually cost, but I doubt it's close to $700.

Richard L.
Title: Re: Am I going to regret not buying this crank?
Post by: nimrod650 on 12.12. 2015 16:33
you can see by the prices why they buy a nice a10 and break it for parts
Title: Re: Am I going to regret not buying this crank?
Post by: BSA_54A10 on 16.12. 2015 21:59
The crank represents 40% to 60% of the entire manufacturing cost of the engine which is why so many companies use the same crank on several different capacity engines.
Before you ask, 40 % for malleable iron or steel casting
And 60% for a forging.
Cast cranks are a tad heavy for motorcycles and do not generally get used in high stress engines.

Over time the interstitial defects within the metal itself migrate and it looses strength.
Thus it is a good idea to get them carbonitrided when you pull them out.

BSA cranks are somewhat over engineered so can get ground down a lot further than most would believe.
We had a memebr with an imported A 65 where the crank main was at - 0,15" , yes 150 thou undersized and he rode it like that for a year or so, no problems till he decided to tear it down and saw what was in there.

Metal spraying and welding are totally different processes despite what an ill-informed Wikki ego posted.

Welding is just that, the molten weld metal builds up a molten weld pool on the surface of the crank, thus changing its grain structure if the crank was forged and the grain size if the crank was cast.

Metal spraying splatters the very hot but still solid  surface of the crank with tiny droplets of molten metal which diffuse into the solid crank a very short distance, It does not change the grain structure of the crank unless done too hot or too slow ( to long ) and allows grains to reform and thus get bigger ( weaker ).

Each process has its pros & cons and they are not just 2 different ways of doing the same thing.
Some applications don't care but a lot of times one will be better suited than the other.
Title: Re: Am I going to regret not buying this crank?
Post by: morris on 16.12. 2015 22:43
Metal spraying and welding are totally different processes despite what an ill-informed Wikki ego posted.

Ok, maybe not the right terminology here. Strictly speaking, welding is the joining of two metals by the aid of a third (which can be three times the same metal), so in a sense the phrase " building up with weld" ain't right either...

In both processes the aim is to get the one metal to bond with the other by the aid of heat. Can we thus  agree on using the word "fusion" maybe? *dunno*
Title: Re: Am I going to regret not buying this crank?
Post by: bsa-bill on 17.12. 2015 10:37
Quote
Can we thus  agree on using the word "fusion" maybe?

Only if we also agree that a hacksaw is a fission weapon ;)
Title: Re: Am I going to regret not buying this crank?
Post by: cyclobutch on 17.12. 2015 12:56
Ha - was that where Tony Blurr went wrong in his search?
Title: Re: Am I going to regret not buying this crank?
Post by: morris on 17.12. 2015 18:58
Only if we also agree that a hacksaw is a fission weapon ;)
Let's meet under the Brussels Atomium and give it a try.  *smile*
Title: Re: Am I going to regret not buying this crank?
Post by: A10Boy on 17.12. 2015 19:26
Whether its right or wrong to buy and break up a good bike, has anyone noticed how Mr M B Transits' prices have gone through the roof recently? A good crank should only cost say £300.

Title: Re: Am I going to regret not buying this crank?
Post by: edboy on 17.12. 2015 21:13
h no, does it mean i will have to insure the crank separetely from the rest of the bike ? as its agreed value only
Title: Re: Am I going to regret not buying this crank?
Post by: BSA_54A10 on 18.12. 2015 10:49
Metal spraying and welding are totally different processes despite what an ill-informed Wikki ego posted.

Ok, maybe not the right terminology here. Strictly speaking, welding is the joining of two metals by the aid of a third (which can be three times the same metal), so in a sense the phrase " building up with weld" ain't right either...

In both processes the aim is to get the one metal to bond with the other by the aid of heat. Can we thus  agree on using the word "fusion" maybe? *dunno*
Well if this was a conversation down the pub, I would not give a wrinkled rats rectum about correctness,
However this is a conversation in cyber space and as such it will persist forever.
Even worse it is searchable and indexed so others will also find the wrong answers and thus an urban myth is born.

The defining thing about a weld is not how it is made.
It is the fact that the microstructure is CAST becuse all parties to the process are at some point in time were MOLTEN
The one and only exception to this is vacuum welding where neither pars get particularly hot and the microstructure of both parts is unchanged.

By definition flame spraying is a BRAISING process because the parent material is not molten at any time but the filler ( or build up material if you like ) is molten.
Thus the parent material more or less retains the microstructure that it had before the process
Title: Re: Am I going to regret not buying this crank?
Post by: morris on 19.12. 2015 23:50
Well if this was a conversation down the pub, I would not give a wrinkled rats rectum about correctness

Lucky we aren't in a pub then because we would now be somewhere at our tenth pint, and no one wouldn't understand anymore what we're babbling about... *smile*

Quote
However this is a conversation in cyber space and as such it will persist forever.

That's why we need to mind our language... *whistle*

Quote
Even worse it is searchable and indexed so others will also find the wrong answers and thus an urban myth is born.

Forums like this one are there to discuss, learn, and correct, which, after your thorough explanation, made me come to the conclusion that I wouldn't really trust metal spraying on a cranck journal...
OTOH, don't know if I'd trust welding either. *conf*
Title: Re: Am I going to regret not buying this crank?
Post by: BSA_54A10 on 24.12. 2015 05:09
I and only if and that is a very big IF it is done properly by a good well experienced operator it will be stronger than the welding build up method.
Note the if's.
Now days people who know what they are doing are few & far between.
modern equipment means you simply dial in the data and press the start button.
Fine if they actually know exactly what the crankshaft material is and how it was made.
Title: Re: Am I going to regret not buying this crank?
Post by: RichardL on 24.12. 2015 06:59
Trevor,

Is it safe to say that the materials and methods (forging, I think) used in making BSA crankshafts in the '50s and '60s were not so sophisticated in metallurgical structure (such as alloying) as to make fusing common welding media to the journals a big problem? Of course, the condition applies that the work be done by a professional using high-quality, purpose-built crankshaft welding equipment.

Richard L.
Title: Re: Am I going to regret not buying this crank?
Post by: BSA_54A10 on 24.12. 2015 10:13
A yes and no type of question.
Twin cylinder BSA cranks were drop forged from a high strength forging alloy. which of course I will remember 2 minutes after I hit the post button.
They were also made from primary forging billet ( all virgin metals used to make the billet ) so would have been as good as they knew how.
A simple logic behind this as forging is very expensive so you want to reduce bad forgings to a minimum so you use good materials.
The two big things that have changed is better allys are now available and better heat treatments are now available.
The actual composition of most metals have become a lot tighter as assaying methods have become a lot cheaper and unbelievably fast.
You can do a mag resonance assay in real time as comparred to 6 hours by wet means.
Also computers have allowed real time TTT ( time temperature transformation ) analysis so I can now accurately manipulate the microstructure at any depth within the crank that I like.
Back in BSA's days every time you wanted to change some thing you had to cut a good crank up polish, etch & examine the structure under a microscope to see if it worked.
Now it can be modled on a computer with 100% accuracy.

However a casting is a casting is a casting and weld build up will always have a cast microstructure so the grains will run from the old crank face up towards the air / weld surface.
Some of it will be dead perpendicular to the journal and some will be at an angle in the direction of build up.
The very best you can do is to solutions heat treat then recrystalize to a  finner grain structure with no directional orientation.
This, engineering wise adds no strength to the crank, unless it was originally a cast crank, you are just building up coating on the outside so it will never have the same strength as it did when new .
Unless welding has changed a lot you used to need a weld pool 3 times the depth you were trying to build up so to add 1mm you need a 3mm pool depth so 2 mm of old forged structure will get replaced with weaker cast structure.

Metal spraying will not cause the loss of any of the original forged microstructure if done properly so if you were building up the same 1 mm you would only have 1mm of cast microstructure and around 0.5 to 1 mm of modified forged structure so it should be stronger when done properly.
Title: Re: Am I going to regret not buying this crank?
Post by: terryg on 24.12. 2015 13:02
Re. crank materials and processing - I've seen references to BSA having had a very competent metallurgical group.  Does anyone have any further information on this?

The 'Triple' crankshaft, twisted into shape when hot, may be a testament to the capability.

Just curious - as the large company in which I worked originally had huge in-house technical breadth dating from WWII and just after.  Sadly all dismantled to assuage the wrath of the bean counters in the 1970/80s (at about that time the apprentice school was closed too).
Title: Re: Am I going to regret not buying this crank?
Post by: RichardL on 24.12. 2015 14:17
Trevor,

Thanks for that great answer. Very intereisting discussion of grain structure and testing methods. Takes me back to the one materials class required when your major is Electriclal Engineering. This brings me to another question. I'm digging down because my next rebuild will most likely include journal welding. If I understand it correctly, forging changes grain size, shape and orientation to increase strength. In a crank, I assume the added strength is for both torsion and bending. So, the question: would 2mm (or, even more) of grain-structure change due to weld penetration make much difference in the overall strength that has been added core-deep by forging?

Sorry if seems I'm trying wear out your fingers with typing.

Richard L.
Title: Re: Am I going to regret not buying this crank?
Post by: a101960 on 24.12. 2015 14:22
Quote
Sadly all dismantled to assuage the wrath of the bean counters in the 1970/80s (at about that time the apprentice school was closed too).
Yes, I too saw all this happen when I worked at Thorn EMI. Sir Jules Thorn built the company up from nothing, and while he was alive he had a policy of expansion and aquisition. Now there is nothing left of this once great company. In quick succsession the apprentice school, and the research and development department was closed, followed by the sell off of all the assets. That is the British business model unforunately. Now the only thing that we make in the UK is redundancies. If you wanted to bring Honda for example to is knees, then all you have to do is hand over the management of the company to to British managers and accountants. Job done!
Title: Re: Am I going to regret not buying this crank?
Post by: bsa-bill on 24.12. 2015 16:33
can't recall at the mo just what did come out of the ashes of BSA. BSA Regal still do stuff (other than the attempt to get back into bikes)
http://www.bsa-regal.co.uk/?category=none&page=aboutus (http://www.bsa-regal.co.uk/?category=none&page=aboutus)
and I had an idea alloy wheels came about from BSA-  could be way off tho
I've read somewhere that Dennis Poore hived of the metal expertise the BSA were known for although I think he himself knew a bit about that side of things - dunno.
Yes management went from brilliant from   WW1 and WW11 to allowing the follies of the Dockers.
BSA were way ahead of government in both wars, having  foreseen hostilities and pre ordered vast amounts of stock.
Title: Re: Am I going to regret not buying this crank?
Post by: Greybeard on 24.12. 2015 17:26
...I had an idea alloy wheels came about from BSA...
I've seen BSA allow wheels. I didn't know they had any connection to our BSA.
Title: Re: Am I going to regret not buying this crank?
Post by: bsa-bill on 24.12. 2015 19:02
Quote
I've seen BSA allow wheels. I didn't know they had any connection to our BSA.

And I think you are right to think so, they are I think a Malaysian Company, no I came across some reference to BSA expertise in metallurgy (and alloys - DOH) which I can't find at the moment, but the depth of knowledge of metals needed to compete in all the fields they did speaks for itself really
Title: Re: Am I going to regret not buying this crank?
Post by: nimrod650 on 24.12. 2015 19:18
Whether its right or wrong to buy and break up a good bike, has anyone noticed how Mr M B Transits' prices have gone through the roof recently? A good crank should only cost say £300.
same old story its worth what anyone will pay and if he can get £1000 mine must be worth A £1000 you will get someone asking £25000 for a  r.g.s  and soon they are all £25000 plus thats life
Title: Re: Am I going to regret not buying this crank?
Post by: nimrod650 on 24.12. 2015 19:40
regarding cranks on british bikes and the final chapter without wishing to upset anyone by swearing the last norton twins that were made the cranks were taken to a local firm  to be ground as the factory machines were worn out
Title: Re: Am I going to regret not buying this crank?
Post by: morris on 24.12. 2015 23:19
Keep it coming lads. Love the way this post is heading...!
Title: Re: Am I going to regret not buying this crank?
Post by: BSA_54A10 on 25.12. 2015 00:40
Trevor,

Thanks for that great answer. Very intereisting discussion of grain structure and testing methods. Takes me back to the one materials class required when your major is Electriclal Engineering. This brings me to another question. I'm digging down because my next rebuild will most likely include journal welding. If I understand it correctly, forging changes grain size, shape and orientation to increase strength. In a crank, I assume the added strength is for both torsion and bending. So, the question: would 2mm (or, even more) of grain-structure change due to weld penetration make much difference in the overall strength that has been added core-deep by forging?

Sorry if seems I'm trying wear out your fingers with typing.

Richard L.

Yes you are correct.
Metal spraying will yield the strongest crank.
However BSA cranks were way over designed so a moot point about drop in strength due to changes in grain structure caused by the welding.
Get the finished product nitrided and it will be more resistant to failure than it was when new.
Be sure to tell whoever is doing the build up you are going to nitride it as it might make a difference to what they use to do the build up with.
For all I know they could use a nitrogen wire to do the build up so you get a double benefit.
Title: Re: Am I going to regret not buying this crank?
Post by: A10Boy on 26.12. 2015 12:04
Apologies if someone has already mentioned this but they were EN49B

Title: Re: Am I going to regret not buying this crank?
Post by: cyclobutch on 29.12. 2015 13:21
h no, does it mean i will have to insure the crank separetely from the rest of the bike ? as its agreed value only

Well I suppose it would be another item you should point out to them as a modification whether it has been sprayed or welded.