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Re: My A70 [Re: Ray Elliott] #725941
02/17/18 10:51 pm
02/17/18 10:51 pm
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NickL Offline
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I think you are mis-construing it Dave, The Timing side bush is narrower and the thrust is effected by the washer running on the machined recess in the case
it's about 54mm dia. the shims only set the distance that thrust washer sits off the end of the crank, they are effectively a spacer to set the distance the thrust
washer sits on it's shoulder they do not act as a thrust. This set-up also uses drive side shimming as per the A65 as well, you set that first then the timing side.

The set-up i have done on the broken cases differs from this in as much as i have had a TS bush made as a single item which forms the inner thrust as well,
rather than using the inner thrust ring that sits in the cases, as the mounting pips for that ring were trashed. As the bush is a solid leaded bronze item, my outer
thrust washer recess is smaller and uses the face of the bush as well as the recess, it's 50mm rather than the a70's 54mm.


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Re: My A70 [Re: Ray Elliott] #725945
02/17/18 11:05 pm
02/17/18 11:05 pm
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Interesting thread.
I'm current in the process of having an A10 crank modified to fit into my A70 cases, (unless someone out there has got a spare A70 crank). I want to retain the timing side bush as I feel that the combination of having an outboard thrust washer helping to maintain oil pressure coupled with a cartridge oil filter, I should get decent longevity out of the engine. Also it's one of the defining differences to the A65.

I'm using the inner race of a needle roller bearing (IRB2014 Imperial Inner Race 1-1/4x1-1/2x22.475) as a sleeve to bring the A10 timing side journal up to the 1.5" dia of the A70 bush. Due to the A10 journal being longer than the A70, my thrust washer will fit over the end of the the journal and effectively clamp the new sleeve bearing onto the crankshaft by the worm drive pinion nut. I don't envisage using any shims if I can get the machining of the bang on, or I'll make a bespoke inner thrust bearing to accommodate the difference.

The question is what is the factory recommend end float for the A70 configuration? I would have thought it may be covered in a service bulletin, but I have yet to find it mentioned anywhere.

With a standard late A65, the 1.5 to 3 thou float would increase as the engine gets up to temp and the crankcases expand. With an A70 set up, I would envisage that the end float would actually decrease and the material around the timing side bush expands, therefore 1.5 thou might not be enough.

Re: My A70 [Re: Ray Elliott] #725954
02/18/18 12:53 am
02/18/18 12:53 am
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3-4 thou on the timing side 1.5-3 drive side. (if you are using a roller drive side.


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Re: My A70 [Re: Ray Elliott] #725974
02/18/18 5:02 am
02/18/18 5:02 am
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I got that the timing bush is shorter and recessed into the case. So the outer thrust washer is running on the aluminum case (and maybe the end of the timing bush)? That was what I objected to. If two flanged bushes were used for the crank (with the outer flange in the case recess), all the shimming would be on the outer thrust washer and it would run against a proper bearing (meaning replaceable if needed).
I am not clear on why the drive side shimming is needed. That controls the crank movement to the left and the thrust flange of the timing bush controls the right.

Re: My A70 [Re: NickL] #726007
02/18/18 10:11 am
02/18/18 10:11 am
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Originally Posted by NickL
3-4 thou on the timing side 1.5-3 drive side. (if you are using a roller drive side.


I'm with you on the 3 - 4 thou on the timing side, but what's the point of shimming the drive side also to 1.5 - 3 thou? The sectional view in the parts catalogue doesn't show any shims on the drive side.

Re: My A70 [Re: Ray Elliott] #726060
02/18/18 7:33 pm
02/18/18 7:33 pm
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DMadigan
Yes you are correct and that's what BSA did. In my case I am having a solid bronze bush made up so the thrust washer will bear against that - Its quite thick so I'm OK with that. I know it will touch the Aluminium casing as well but I don't think that will cause a problem. It's certainly better than using the main roller bearing as the end stop in that direction which is what happens normally :-)


SJW
Re: My A70 [Re: DMadigan] #726077
02/18/18 10:03 pm
02/18/18 10:03 pm
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NickL Offline
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Originally Posted by DMadigan
I got that the timing bush is shorter and recessed into the case. So the outer thrust washer is running on the aluminum case (and maybe the end of the timing bush)? That was what I objected to. If two flanged bushes were used for the crank (with the outer flange in the case recess), all the shimming would be on the outer thrust washer and it would run against a proper bearing (meaning replaceable if needed).
I am not clear on why the drive side shimming is needed. That controls the crank movement to the left and the thrust flange of the timing bush controls the right.



It was probably just done as a matter of course. ie They had always done it.
It does stop any chance of the bearing rotating on the shaft , which isn't a bad thing.


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Re: My A70 [Re: Servodyne] #726092
02/18/18 11:39 pm
02/18/18 11:39 pm
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To my mind the shimming on the drive side becomes redundant EXCEPT to align the two halves of the roller bearing SKF bearings claim they can be up to 1.5mm out (in one direction obviously!) But I'm aiming to stay the right side of 0.25mm. With my setup I can do that with just the shim bucket between the inner bearing race and the crank


SJW
Re: My A70 [Re: Ray Elliott] #726192
02/19/18 11:11 pm
02/19/18 11:11 pm
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Bega NSW Australia
Mark Parker Offline
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I don't know why the factory didn't just put a heavy series needle roller in there, with a bearing plate outside the alternator to control end float. And the bonus is it also prevents shaft deflection and primary misalignment.

This bearing carrier is one piece, rather than using spacers into the alternator.

[Linked Image]

The dimples are to clear the inspection plate screw lugs on the chain case. The hole is for timing, with a drilled dimple into the alternator rotor.

[Linked Image]


mark
Re: My A70 [Re: Mark Parker] #726194
02/19/18 11:33 pm
02/19/18 11:33 pm
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What a simple, yet elegant solution ! It is a wonder why BSA didn't do this. After all, it is a sort of extrapolation of what was done with their B31, 33, etc singles. Using the outer ball bearing drive side main to locate the crank.
That bearing carrier is a neat job, Mark.

Last edited by Triless; 02/19/18 11:37 pm.
Re: My A70 [Re: Mark Parker] #726291
02/20/18 11:48 pm
02/20/18 11:48 pm
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Hi. Is that another bearing you have fitted to the plate behind the clutch as well?
Steve.


SJW
Re: My A70 [Re: Ray Elliott] #726295
02/21/18 12:04 am
02/21/18 12:04 am
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I did have a similar arrangement on my outfit at one time but when i ran a 36 tooth engine sprocket i had to machine the alternator carrier off.
I never got around to re-engineering it. Just used a duplex chain as they are more forgiving to the deflection in the crank.
The clutch outrigger is a must on performance a65's. Racers were doing that since the 60's in the UK.

I was told by a couple of guys out of the competition shop that it was the redesign of the timing cover and subsequent re-drilling/sealing
the cases that stopped the whole end feed thing as a production item. MONEY! Les Mason got out and did it. Devimead, he sold dozens
then SRM bought Devimead and sold hundreds. There was a guy who was casting the timing covers with an end feed in as well, years ago.
They looked more square than the originals, saw a few at race meetings.
If i was going down that path i'd make the timing cover as a separable item from the box cover, just to complete the picture and make things
more convenient.


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Re: My A70 [Re: Ray Elliott] #726296
02/21/18 12:19 am
02/21/18 12:19 am
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I've just put the modified bottom end together on this damaged engine, all worked out quite well. The thrust on the timing side works well.
The shimming on the drive side main, although not really necessary does mean you don't need so much shimming on the drive sprocket to get the chain alignment correct.

Steve, if you are going to make a gearbox outrigger, the traditional way is to use a sealed bearing and machine the inner to 20.5mm (a tight fit on the mainshaft) Then cut
the projecting bush off. Various 20mm ID bearings are around but you'll have to watch the width of them. You can make up a new plate or machine the original as Mark has done.


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Re: My A70 [Re: Ray Elliott] #726298
02/21/18 2:35 am
02/21/18 2:35 am
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I made a gearbox outrigger this way:
[Linked Image]
The nut was an extension shaft into a ball bearing in the primary cover. A three arm lifter in the shaft and triple lift plate in the cover pulled out the pressure plate. Talk about light lever force, I had to add a spring to return the lift plate because the friction in the lifter bearing was adding so much torque the lifter would not return.
The bearing in the sprocket door is less noticeable.

Re: My A70 [Re: Ray Elliott] #726303
02/21/18 6:13 am
02/21/18 6:13 am
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Bega NSW Australia
Mark Parker Offline
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The other thing the bearing outside the alternator does is make it much more difficult for the crank to flex in the middle. If you get a plastic ruler and sit it on a couple of blocks with an overhang on one end, when you push it between the blocks the end of the overhang flexes up. If you secure the end of it, its harder to flex the middle.

What a wild looking mod Nick. I got the longest alloy bar lever I could find to get some mechanical advantage on the clutch. I was thinking of extending the lift lever in the case but it's not that bad, even with the heavy 4 spring unit I use.


mark
Re: My A70 [Re: Ray Elliott] #726325
02/21/18 1:21 pm
02/21/18 1:21 pm
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Too many interesting ideas!! I need to put mine back together before I get carried away!


SJW
Re: My A70 [Re: Ray Elliott] #726333
02/21/18 3:35 pm
02/21/18 3:35 pm
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argyll. scotland, uk
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https://www.ccm-britain.co.uk/?xhtm...m.html&category=&xsl=diagram.xsl

item 5 on the diagram, Mark Cook of PES makes a bearing / clutch back plate for B50s, fits A65s too, although the one I got was a slack fit, my motor was not typical.


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Re: My A70 [Re: Ray Elliott] #726367
02/21/18 11:50 pm
02/21/18 11:50 pm
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DMadigan Offline
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This is another way that I did it:
[Linked Image]
The bell housing sits over the clutch basket and the short spud on the outside runs on rollers (same as the clutch hub). A boss was welded into the primary cover and a steel race was pressed into it. Unlike the other one this used the stock lifter.

Re: My A70 [Re: Ray Elliott] #726384
02/22/18 2:18 am
02/22/18 2:18 am
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Nice one Dave, outside the box again.


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Re: My A70 [Re: Ray Elliott] #726641
02/24/18 8:33 am
02/24/18 8:33 am
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Bring in the 'Comfy Chair'
Re: My A70 [Re: NickL] #726644
02/24/18 10:34 am
02/24/18 10:34 am
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Nick, this is impressive stuff ! Why do you tell me not to believe all you say ? Is a weird mental anomoly why you were transported to Botany Bay ?
Incidentally, will you be going to the International BSA Rally this year at HallsGap. It is near where I live !

Re: My A70 [Re: NickL] #726696
02/24/18 10:05 pm
02/24/18 10:05 pm
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Nick. Thanx for that - There appears to be an extra step in the crankshaft I wouldn't expect - The A70 uses a thrust washer with a 3/4" ID - are you using something bigger?
Steve


SJW
Re: My A70 [Re: Steve Wilson] #726706
02/24/18 11:07 pm
02/24/18 11:07 pm
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Originally Posted by Steve Wilson
Nick. Thanx for that - There appears to be an extra step in the crankshaft I wouldn't expect - The A70 uses a thrust washer with a 3/4" ID - are you using something bigger?
Steve


The thrust ID is 22mm, it is a convenient size for shims, (i had some). I am using the standard timing pinion with it.
The washer sits 10 thou below the 'face' as otherwise it would foul on the oil pump body in a couple of spots.
As i said, i used a 3mm thick 50mm od stainless washer for the thrust, nothing fancy. It ended up 2.8mm thick after flatting on a stone.
The bush is 660 Leaded bronze, i don't like PB1 or hard gear for these. The inner flange is 3.6mm thick so does not use the old thrust ring.
As you can see, the locating lugs for that ring were trashed well and truly by the previous builder's mistakes.
I normally don't use one piece bushes and prefer the original steel housed type, but as i needed the two thrust areas it was the easiest way.

Stephen, i don't know if i will be at the rally as i may be moving house later in the year, i will do my best to get there though.
They only sent me to Botany because Port Arthur didn't allow sidecar racers! (they reckoned there were limits to the nutters they would take)


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Re: My A70 [Re: Ray Elliott] #726847
02/26/18 11:47 am
02/26/18 11:47 am
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Nick - My locating lugs are trashed as well and I had also aimed to do without the thrust ring - I think its better without anyway. Mine works out about 4.4mm thick. (Whats left of the locating lugs is 3.9m deep on mine) I'm going to change to your design for the step in the crank as it locates the shims properly.
Incidently I have both types of Cam gear pinions and mine are almost Identical width - the ones measured earlier in this thread were about 0.5mm different.
Steve


SJW
Re: My A70 [Re: Ray Elliott] #729038
03/18/18 4:33 pm
03/18/18 4:33 pm
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OK - Parts are machined now and crank balanced so its all back in the shed awaiting rebuild. Spent this afternoon fitting Helicoils to all the barrel stud positions.
Crankcase was line bored and Bush was specially made. They also re-cut the anti rotation flats a bit deeper as they had been trashed.
Rebate for the thrust washer is about 50mm x 3mm a bit smaller diameter than the actual A70 version.
I'm quite pleased so far - What does the panel think?

Attached Files P1060956.JPGP1060962.JPGP1060964.JPG

SJW
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