Expansion link block

[jscarmozza]

Does an expansion link slide block have to be 'square' or could it be round? Trying to take the easy way out and not have to square off the round ended slots left by the end mill.
John

[LVRR2095]

Even with a “square” link block, the ends of the slot can be as you have machined them. The slots just need to be enough longer so that in full gear the block doesn’t reach the ends of the expansion link’s slot.

[Bill Shields]

to maybe answer your question...recommend 'square' block so that you have a contact SURFACE rather than a contact 'POINT' which would be the case if the block is round.

you may want to look at 'squaring off' the ends of the link so that you can get the proper travel as previously suggested.

[LVRR2095]

Here is the expansion link on Big Boy. Square link blocks and rounded ends on the slots.
https://oldmachinepress.files.wordpress ... wheels.jpg

[jscarmozza]

Thanks Keith and Bill. I never saw a round block either, but there's no harm in asking. I was thinking about putting a rolling sleeve on it to reduce wear, but I'll stick with conventional wisdom and make a square block.

[Bill Shields]

I would worry about wear in the link also

[Berkman]

I thought someone did put a round link " block" in a valve gear on here with positive results.


If stephenson, the eccentrics and eccentric straps will have likely as much if not more wear. Would consider making bushings that fit between the eccentrics and eccentric straps, then you can harden the straps/eccentrics and the bushing will take the wear. Might be good move in the long run.

[Bill Shields]

Not Stephenson..Walschaert...from the outside shape and attachment tab..

Unless been sitting around rusting appears to be made from HRS which would most likely suffer badly from a roller point contact block.

[FKreider]

You could always install a round "block" with bushing as you suggested and if it wears then you could swap it out for a traditional square one.

At some point all locomotives will wear in places and need some level of overhauling in the shops.

[jscarmozza]

Good eye Bill, it is hot rolled steel. It started out as an experiment using my pantograph that tuned out so well that I figured I'd use them. I was thinking about the roller sleeve too, but like I said before, I'll stick with the conventional method. I only made blocks once before and it was a royal pain in the neck getting the fit right...no easy way out.

[Greg_Lewis]

...
I only made blocks once before and it was a royal pain in the neck getting the fit right...no easy way out.

I did my links on a rotary table and used the table also for the blocks. A longer piece of material was set up on the table and cut to the right arc on both edges and then I just cut off a couple of bits for the blocks. Since the rotary table was zeroed out to the mill spindle setting off the radius was easy and there was no pain involved.

[hoppercar]

Round is fine....just so long as the block doesn't bottom out and bind up in full gear