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MikeG
MikeG
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#821461 08/28/20 8:42 am
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Mito Offline OP
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Hey everyone, as I have posted before, I am restoring a 71 T150 and upon strip down, found the engine had a mismatched centre case. I tried all of the usual tricks but when measured, it was found to be 005" out of alignment so some serious surgery needed.
I made up some bronze bearings and fitted to the centre mains to support a 40mm boring bar. I welded up the journals on the outer cases and bored them back to size in alignment with the centre mains. I did it all in my lathe by attaching the cases to my cross slide and driving the boring bar with the chuck using a universal shaft made from Landrover steering joints. It has been a lot of work but saving the cases and the original numbers was worth it. The tooling wont go to waste as I have several sets of mismatched cases to reclaim for future projects.
https://imgur.com/a/O6oPCdZ
https://imgur.com/a/rOwivSA
https://imgur.com/a/5MgAVua
https://imgur.com/a/WsJuaKv

Last edited by Mito; 08/28/20 8:58 am.

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Brilliant, I love stuff like this.

How did you attach the cases to the top slide? Its hard to see how from the pictures although I guess they are attached just at the bottom? Did you have problems with chatter with this arrangement?

What boring bar did you use, a commercially bought one or home brew?

I am interested as I have pondered this job myself but haven't dived in yet.

Excellent work!.

John

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Hi John, the cases are held down to a steel plate via the sump hole which is in turn bolted to the cross slide. The boring bar is just a piece of 40mm bright steel bar that I drilled to take some square HSS tool steel. Used a dial gauge to measure the tool adjustment to machine to size. No chattering as the cases and bar are a unit. It was only bolted to the lathe to drive the bar and provide power feed. I took a whole heap of photos if you want more info.


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Hi Mito,

Thanks for the reply. I am interested in more info.

I have used homemade boring bars before with adjustment similar to how you describe and it is a bit fiddly to get the level of adjustment required if, for example, you only need to take off a thou or two. I was wondering if you had a different method but apparently not.

Good work and thanks for sharing.

John

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Great work, Mito, — another triple saved to go back on the road.

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Hi John, you can achieve very good accuracy on the boring bar if you make it with holding screws and a pushing screw at the back of the tool. Adjust by leaving a bit of tension on the holding screws and wind the tool out using the pushing screw. You will see in one photo, I am using a dial gauge to measure tool movement.


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Mito Offline OP
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Thanks Tridentman, Im looking forward to getting this one back on the road. I have enough Trident stuff that I have been collecting over the years to put another three together. Im putting two Rob Norths together, a R3 and a T150 version and a matching number mongrel that will use all of the bits left over so hopefully a total of four resurrected from the dead.


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Since you have "moved" the timing side crankshaft position how well are the timing gears meshing?

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Hey Steven, the reason to re align is because the crankshaft is actually in the wrong position relative to the timing and drive side cases.. By line boring as a unit, everything is back where it should be. Total out of alignment was just under .005" which is enough to load up the centre mains and cause them to fail but well within the tolerances of the spur gear mesh. Both timing and drive side cases were remachined.


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Are camshaft holes align within the cases?

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Instead of remachining the case bearing locations you could have remachined the case locating dowels and decked the cylinder opening.

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Originally Posted by DMadigan
Instead of remachining the case bearing locations you could have remachined the case locating dowels and decked the cylinder opening.

How much clearance is there between the crankcase lip and the corresponding recess in the other piece? this would limit your scope for moving the cases in relation to each other.

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I have not measured it but it is easy enough to walk around the lip when the case is on the mill if needed.

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Mito Offline OP
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Hey Guys...in reply to Adam M, yes cam tunnels in alignment and cams turn freely. Dave Madigan, I looked at all possible resolves. Even with no dowels in place, I still could not get the cases to come close, it always had a stiff feel to the crank. I know this way was a truck load of work but Im pretty satisfied I have the cases in alignment and the crank now turns effortlessly. I have quite a few other sets of mismatched cases I will apply the same resolve to which means more triples on the road which has to be a good thing.


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71 A65 Firebird
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75 Honda XL 350
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Originally Posted by DMadigan
Instead of remachining the case bearing locations you could have remachined the case locating dowels and decked the cylinder opening.

This view is the consensus position. I was out at Formula Tooling yesterday. the proprietor, Colin Webster has done five case alignments. His view is that it is not advisable to line bore the cases. Using the centre case as the datum The outer case dowel holes are bored oversize in the correct position to bring the crank and cams in to line. The case are then located with stepped dowels.

His observation is that the crank/cam relationship is correct on all outer cases he has dealt with and should not be changed.

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Originally Posted by Mito
Hey Guys...in reply to Adam M, yes cam tunnels in alignment and cams turn freely. Dave Madigan, I looked at all possible resolves. Even with no dowels in place, I still could not get the cases to come close, it always had a stiff feel to the crank. I know this way was a truck load of work but Im pretty satisfied I have the cases in alignment and the crank now turns effortlessly. I have quite a few other sets of mismatched cases I will apply the same resolve to which means more triples on the road which has to be a good thing.

I think you might eventually run into trouble when you move a crank/cam distance too far.


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