crankpin ends

[rudd]

I found this image of a 5" gauge engine in the UK. I'd like to do my pin ends like this as opposed to a hex fastener. I see that the FN and Chloe are drawn with a round disk with flats milled on for a wrench, which is less objectionable to me than the hex, but still not what I am looking for.
Does anyone know how this is done?

crankpin end.JPG (13.53 KiB) Viewed 3873 times

[LVRR2095]

That “disc” is actually part of the crank pin…it is not a separate piece. The bearing is split and half is placed on the main rod, then the rod is mounted to the crank pin in the recess. Finally the rear half of the bearing is inserted and held in place by the piece with the through bolt. The bearing is then adjusted with a tapered key. This is known as a strapped and wedged big end.

[rudd]

thanks.
I think I found a good way to fake it, thanks to Mr. Porter. Hole through pin, nut goes on the inside. That's some mighty fine work to be done in 1" scale.
The construction series I found on the 1" scale engine does not have the flange integral with the crankpin, builder must have done the same thing I am contemplating.

crankpin collar.JPG (8.49 KiB) Viewed 3813 times

[LVRR2095]

Why fake it? Strapped and wedged rods work very well and are prototypical.

[rudd]

Why fake it? Strapped and wedged rods work very well and are prototypical.

Uh, yeah, but the pins are made and in the drivers, and the rods are made. If I had it to do over, I would not have used the "round bushing in a solid rod" design.
And if I am modeling a Porter, which I am, I may be doing it prototypically.

[rudd]

Here's the 5" gauge engine before the ends were installed.
I think I remember what I am thinking of from the tiny little porter I worked on at the museum - seeing a nut on the inside end of the pin.

https://www.rmweb.co.uk/community/uploa ... 538237.jpg

[Glenn Brooks]

That “disc” is actually part of the crank pin…it is not a separate piece. The bearing is split and half is placed on the main rod, then the rod is mounted to the crank pin in the recess. Finally the rear half of the bearing is inserted and held in place by the piece with the through bolt. The bearing is then adjusted with a tapered key. This is known as a strapped and wedged big end.

LVRR2095,
Any chance you could direct me to an exploded diagram of the assembly you describe? Particularly like to see what gets adjusted with the taper key, and any parts needed to do that.

I’ve got a regaugimg project (14” to 15”) coming up on an old Hurlbut Atlantic, where this method might be perfect. We plan to shave the side rods down .50” each side and move the drivers outwards that amount on the existing crank pins.(these Hurlbuts have really beefy, thick, overbuilt side rods). This might be a method to do that...

Thanks
Glenn

[FKreider]

I'm also wondering what keeps the tapered key in adjustment?

I've seen this plenty of times but never gave it much thought.

[Rich_Carlstedt]

Frank , Anything less than 7 degrees is considered a locking angle
Different engineers used there favorite , but that was usually between 3 and 4 degrees

Rich

PS You see it on collets , a Morse taper is locking , while a R 8 which is steeper than 7 degrees-- uses a drawbar

[rudd]

I've seen a small bolt tapped into the side of the rod to press against the key. Ones I saw had a locknut. This was on the Rogers 0-4-0 at the museum.

Here's one on Argent 7. No locknut.

[NP317]

On my Allen Ten Wheeler.

It has worked for well over 500 miles running never even requiring adjustment, which is possible to do compliments of the prototypical design.
Yes, the crank pin is threaded for an external hex nut, not what you seek. (No picture available.)
RussN