Building the 2.5" Scale Shay

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Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Wed Jan 10, 2018 12:52 pm

No idea why the pictures are rotated incorrectly... They're right side up on my computer
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
Posts: 1248
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Wed Jan 10, 2018 1:55 pm

Any thoughts of using zerk fittings? I know, not prototypical, but they have the check valve that would allow the grease to maintain pressure. If they would fit, you could put zerk fittings inside your cups?

Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Wed Jan 10, 2018 2:04 pm

I may switch to zerks if these cups don’t work how I want. I think they’ll be fine for the wrist pins though, they shouldn’t need much grease. As for the big ends, I would still have the same problem with the zerks as I do the cups. Can only get a small amount in there before it comes out the seam instead of going into the bearing. Looking at my reference pictures, it appears the full-size ones had the same problem though. There’s always grease oozing out of where the two bearing halves meet.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
Posts: 1248
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Wed Jan 10, 2018 2:32 pm

Ahh I see. I wonder if you could use something soft to squish in between the seam to minimize the "leak". Like use a couple pieces of plasti-gage and leave it in there.

Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Thu Jan 11, 2018 11:43 am

rkcarguy wrote:
Wed Jan 10, 2018 2:32 pm
Ahh I see. I wonder if you could use something soft to squish in between the seam to minimize the "leak". Like use a couple pieces of plasti-gage and leave it in there.
I dont know. I wonder what other people with real split bearings have done. Whatever is used to plug the gap needs to be able to compress as the bearing wears and I tighten the wedges
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

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NP317
Posts: 1916
Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon

Re: Building the 2.5" Scale Shay

Post by NP317 » Thu Jan 11, 2018 12:30 pm

Properly designed and manufactured split friction bearings are supposed to work without frequent re-greasing. The lubricant used is important.
A thin film of grease (or oil) keeps friction at bay. For axle bearings, the upper bearing radius should be slightly larger than the axle, "squeezing" the lubricant between both surfaces as the axle rotates. Grease cellars in steam locomotive driver axles keep a thin film on the top-journal bearing surfaces. Grease blocks are held in a carrier that is pushed (by springs) against the axle bottom.
This system cannot be used on a full split bearing.

Any method that wipes some grease or oil onto the surfaces should be fine, including grease just sitting in the bearing "gaps". A long-polymer lubricant acts "stringy" and helps pull the lube onto the moving surface. There are such bearing greases available such as moly-disulfides, found in auto parts stores.
Someone with chemistry knowledge can provide better info than I.

A large full-circle split bearing might benefit from waxy-grease, as used on full-sized locomotive rod bearings. The grease liquifies with heat, providing fairly long-term lubrication.
Not simple.

Let the discussions continue.
~RN

Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Thu Jan 11, 2018 12:43 pm

NP317 wrote:
Thu Jan 11, 2018 12:30 pm
Properly designed and manufactured split friction bearings are supposed to work without frequent re-greasing. The lubricant used is important.
A thin film of grease (or oil) keeps friction at bay. For axle bearings, the upper bearing radius should be slightly larger than the axle, "squeezing" the lubricant between both surfaces as the axle rotates. Grease cellars in steam locomotive driver axles keep a thin film on the top-journal bearing surfaces. Grease blocks are held in a carrier that is pushed (by springs) against the axle bottom.
This system cannot be used on a full split bearing.

Any method that wipes some grease or oil onto the surfaces should be fine, including grease just sitting in the bearing "gaps". A long-polymer lubricant acts "stringy" and helps pull the lube onto the moving surface. There are such bearing greases available such as moly-disulfides, found in auto parts stores.
Someone with chemistry knowledge can provide better info than I.

A large full-circle split bearing might benefit from waxy-grease, as used on full-sized locomotive rod bearings. The grease liquifies with heat, providing fairly long-term lubrication.
Not simple.

Let the discussions continue.
~RN
Thanks for the info! I think my grease meets those requirements. I’ve got some #3 soda grease made by Green Velvet. It’s a tacky fiberous grease that I got primarily for my bevel gears, but sounds like it would be a good choice for the wrist pins and split bearings as well. I put a radius on each bearing half at the seams so that should help the bearing pull in the grease.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
Posts: 1248
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Thu Jan 11, 2018 8:24 pm

Something we've done on the splash lubed engines for kart racing, is carefully grind a long teardrop shaped slot/depression inside the connecting rod bearing area. As the crank pivots...ever so slightly eccentric due to the clearance, it will basically create a pumping effect.
These engines start life as 6.5HP tiller motors, and are built cheap, cast aluminum running right on steel. So in stock classes that don't allow billet rods with real bearing inserts, we've figured out all kinds of tricks to keep the rod well lubricated.
I know a friend of mine is a mechanic for our Customs Border Protection Helicopters, and they have this stuff they use in the tail-rotor boxes and bearings that is pretty amazing, I can find out what it is if you'd like. Another friend of mine already got some to use on his dual sport bikes.

Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Mon Jan 15, 2018 9:37 pm

Two steps forward, one step back. Got everything running and was doing a shake down run of the engine. Low and behold one of the press joints of the crankshaft came loose again, I must really not be good at press tolerances.... Used Bruce’s trick of cold chiseling the shaft to make it a tighter fit in the hole and it seems to be good now. Also took the opportunity to fix a minor bugaboo, I had the rear cylinder leading when it should’ve been the front. The crankshaft should be good to go now, but I threw the timing for the rear cylinder out of whack so it needs some more adjusting to get her square. Once I’m happy, I’ll do another hard shake down run like I did earlier and see what happens. Joys of building a steam locomotive.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Mon Jan 15, 2018 11:18 pm


Here's a video of the engine on air. Running nicely two notches back from the corner and about 300 rpm, this equates to a track speed of around 3 mph.
Now to decide on the next part to make, so many options still
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
Posts: 1248
Joined: Tue Aug 22, 2017 10:33 am
Location: Wa State

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Tue Jan 16, 2018 1:30 am

Do you have access to a TIG welder? I wouldn't be afraid of using it to put a few fusion tacks on that crank to keep things from moving again, if so.

Soot n' Cinders
Posts: 791
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Tue Jan 16, 2018 10:08 am

rkcarguy wrote:
Tue Jan 16, 2018 1:30 am
Do you have access to a TIG welder? I wouldn't be afraid of using it to put a few fusion tacks on that crank to keep things from moving again, if so.
I do have a TIG welder here. I’ve tried that approach once before though and wound up pulling the shaft out of square with the crank web. Maybe I was running too hot though. One reason I considered brazing as the next option, it’s not as hot.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

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