Author Topic: Broken case  (Read 809 times)

Offline Superflash

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Re: Broken case
« Reply #15 on: 30.01. 2020 11:20 »
Thanks Swarfy.  After much gnashing of teeth I've come to a decision. I think the SF is a unique beast and it would be a pity to chuck in the towel. Have sourced a decent timing side engine case on fleabay for a reasonable price. Tomorrow I'll grab the last 2 cam bushes from our local supplier. Have also spoken to an engineering shop just up the road. They have all the gear to machine the cases and line bore the cam and crank bushes. I already have a new anti drain ball and spring along with a scavenger pipe. So now I'm going to have to be patient and do some heavy duty saving to pay for it all.  *eek*. Watch this space. Cheers
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Offline Swarfcut

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Re: Broken case
« Reply #16 on: 30.01. 2020 11:58 »
 Next trap (in more ways than one)....The Crankshaft. Read the posts about the crank, the types, the differences and the most important single factor for good engine performance, bearing life and the abilty to ride home rather than on a tow truck, with a rod through the case.

 I will step aside to allow a fanfare to sound, the curtains open, and the spotlights shine on........an important announcement from an esteemed member.

     Additional... Accepted practice these days is to grind the crank main bearing journal just to clean up, rather than sticking to standard undersizes, thus increasing the number of possible crankshaft main bearing regrinds. Choose a smaller undersize solid one piece bush and fit to the case, then line bore the bush to the running clearance. All detailed on the Forum. The bush housing sometimes suffers damage and ovality, remedy here is line boring the case and a custom bush. Leakage here, between bush OD and case, obviously lowers oil pressure on the pump delivery side.
  Camshaft and other simple plain Bronze bushes should be of commercially available standard types. Possibly just needing drilling an oil hole as required. Some pattern parts come with internal scroll oilways, most don't. Heat the cases, as usual practice, bushes should come out easily. Blind camshaft bush removal can be a conundrum.

 Check assets and arrange finance while interest rates are low.

 Cheers.
 

Online BritTwit

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Re: Broken case
« Reply #17 on: 30.01. 2020 13:22 »
I think I have a matched set of BA10 cases stored away along with a spare set of Super Flash cases.  The big problem is the cost shipping from the U.S.

Online Greybeard

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Re: Broken case
« Reply #18 on: 30.01. 2020 14:31 »
Next trap (in more ways than one)....The Crankshaft. Read the posts about the crank, the types, the differences and the most important single factor for good engine performance, bearing life and the abilty to ride home rather than on a tow truck, with a rod through the case.

I will step aside to allow a fanfare to sound, the curtains open, and the spotlights shine on........an important announcement from an esteemed member.


[Cough] I think that may be a queue for me to repeat the mantra "Clean the sludge-trap!".  *smile*

Offline Swarfcut

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Re: Broken case
« Reply #19 on: 30.01. 2020 15:31 »
   Yes, GB, Thanks once more for drawing attention to our old friend the sludge trap. Right on cue with a timely reminder.

 To anyone doing a rebuild.
    Your friendly crank grinder will not mention the vital attention that should be paid to the sludge trap. This is located between the big end journals, and is sealed at each end by screw-in plugs, and on later cranks also located by a radial bolt. So get those plugs out and clean away the accumulated mix of carbonised oil, sludge and bearing metal from previous mishaps. Early crank has just a plain drilled oilway, later crank has a removable tube, which may require violence to extract. All the replacement parts needed are available.

 The forum comes to your aid showing how to do it, with detailed and worked examples together with vivid pictures of what lurks within. Neglecting this  has brought many an owner to tears, as their newly rebuilt engine tightens, locks and sometimes goes bang within a few hundred yards of the first triumphant (until then) test run. You get the crank done again, and guess what?  So, no if's, but's or excuses. Clean out that trap. Thereafter regular oil changes, plus  fitting a modern filter in the return line to the tank to keep the oil clean, will give long engine life.

Swarfy.



 

Offline Superflash

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Re: Broken case
« Reply #20 on: 04.02. 2020 10:32 »
Hi all. Well I found a timing case that's in pretty decent condition other than the dirt/oxidisation etc....

Now the bloke I bought it off claimed it was an A10 and looking at the photo's this appeared to be the case (pun intended...).

It arrived today, and when I placed it next to the broken case that came as part of the motor, there were differences. So am wondering you gents can identify why the changes in the castings, and will it make any difference?

First difference is what looks like a stud tube under where the magneto sits, but above the gearbox mount.

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Offline Superflash

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Re: Broken case
« Reply #21 on: 04.02. 2020 10:44 »
Hmmm. still trying perfect the art of attachments here...

So, 2nd difference is inside the timing chest itself. The new one has a raised bump running horizontally across the top of the timing bush hole more or less from one side to the other, whereas the old one hasn't. I'm wondering if the new case is actually older than the one I had. Case number on the new one is 178, the original case was 231.

Had a good long chat with the guy who is currently boring the cylinders, and he has agreed to machine the cases and line bore the crank and cam bushes.
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Re: Broken case
« Reply #22 on: 04.02. 2020 11:13 »
And my favourite wheel barrow to push
Whenever a crank is out get it CARBO-NITRIDED.
An by preference find some one who does it in an ammonia furnace.
Note I did bot sat Nitrided
Note I did not Carbonised.
The process goes under the trade name of TuffCoat or Tuffride.
If the heat treater starts talking about hardness increases he is talking about the wrong process.

Basically it introduces both Carbon atoms and Nitrogen atoms into the crystal structure, but not enough to chemically react as would be the case with case hardening.
What the process does is substantially toughen the crank and makes it very hard for cracks to propergate to a size where they are big enough to cause failure.
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Trevor

Offline Superflash

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Re: Broken case
« Reply #23 on: 04.02. 2020 11:23 »
Amazingly enough, we have a nitriding oven at work for doing aluminium extrusion dies. It's used for hardening the die bearings where the aluminium flows over. Same thing you're talking about? With regards to a few of the earlier posts, yes, I have taken the sludge trap plugs out and cleaning the whole thing out. Have new plugs, and am wondering if loctite will do rather than swinging a hammer and centre punch? Cheers
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53 BSA SF (WIP)

Offline Superflash

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Re: Broken case
« Reply #24 on: 04.02. 2020 11:32 »
Yeh, me again... *smile* I think I've answered my own question. Looks like the "new" timing case is a pre BA10 model. So assuming the engineer can match them etc, will this case go together with the SF drive side case? Cheers.
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Online Greybeard

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Re: Broken case
« Reply #25 on: 04.02. 2020 11:42 »
Whenever a crank is out get it CARBO-NITRIDED.
.......
Basically it introduces both Carbon atoms and Nitrogen atoms into the crystal structure, but not enough to chemically react as would be the case with case hardening.
What the process does is substantially toughen the crank and makes it very hard for cracks to propergate to a size where they are big enough to cause failure.
Well , that is a piece of useful info! Thanks  *good3*

Offline Swarfcut

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Re: Broken case
« Reply #26 on: 04.02. 2020 12:08 »
     Looks like you struck lucky.
        The basic casting is the same, so should fit. The locating dowel positions the web above the camshaft trough. This narrow drilling is  the breather, running across the engine, exits above the gearbox sprocket.
    Have a look in the PRV cavity.  Early case has a drilling leading DOWN to exit below the oilpump.   Later case drilling goes UP, to connect with a gallery running back, over the timing bush area (the bump) and up to the camshaft trough. There is a small drilling visible to feed oil to the timing gears. Often neglected, worth cleaning out. Originally this later casting could be from a BA Series motor. So for once, you done good.

   Look carefully at the parts. Some have a date stamp below the dynamo cradle, and near/under the primary chain tensioner.  The actual casting number is not the part number, as the same casting may be machined in  different ways as engine  development proceeded. Also an "assembly" complete with fittings eg timing side crankcase with pick up pipe and bushes, will have a part number sometimes closely, but not necessarily, related to the casting number.

 Best buy a Lottery ticket while you have a winning streak.

 

 Swarfy.




 


Offline JulianS

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Re: Broken case
« Reply #27 on: 04.02. 2020 13:47 »
The case type with the raised bump and feed to the cam trough was introduced after engine ZA10 4712, which is about September/October 1950. The first ones after the change did not have the cam trough drilling plugged at the crankcase joint and some leaks happened so the recessed plug at the end of the drilling was introduced.

Online RDfella

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Re: Broken case
« Reply #28 on: 04.02. 2020 17:25 »
BSA55 - nitriding and tuftriding are two different processes. Most steel / iron can be tuftrided but only a few nitrided.
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Re: Broken case
« Reply #29 on: 05.02. 2020 08:07 »
Which is why I emphasied CARBO _ Niriding.
Strait nitriding will add some toughness but is basically an alternative to case hardening.
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Trevor