Building the 2.5" Scale Shay

Where users can chronicle their builds. Start one thread and continue to add on to it.

Moderators: Harold_V, WJH, hwboivin3

rkcarguy
Posts: 409
Joined: Tue Aug 22, 2017 10:33 am

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Tue Jan 16, 2018 11:44 am

It is a bit tricky, you have to run the small cup and then really dive in and hit the power. Wrap a soaking wet rag around the crank with only the weld area exposed. Make your first tack, then jump 180* across and hit it again as quick as possible. Change the wet rag out for another one and cool the part, then do two more, (for a total of 4ea 2-3 fusion puddles 90* apart). You "dive in" quick, apply a lot of power to get the wet out as soon as you can, then get it out of there. If the fusion weld cracks, you may need to use a little bit of fine SS rod.
Unless your crank pin has oblonged it's hole, it shouldn't pull enough to hurt anything. If it has, maybe braze it with some low temp stuff, or take it somewhere where you and a friend could hit it with two TIG welders at the same time. We've done that here in our shop when it's been something critical. Lastly, you can also TIG with brazing rod, it allows you to focus and minimize the heat. Again, dive in, apply a lot of power to get wet out, then get it out of there. It's worth practicing on a piece of scrap to get the settings right.

I've fixed (temporarily and permanently) a lot of stuff this way, where I have to keep heat down due to not melting seals, keeping a pulley running true, etc.

Soot n' Cinders
Posts: 654
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 12:04 pm

rkcarguy wrote:
Tue Jan 16, 2018 11:44 am
It is a bit tricky, you have to run the small cup and then really dive in and hit the power. Wrap a soaking wet rag around the crank with only the weld area exposed. Make your first tack, then jump 180* across and hit it again as quick as possible. Change the wet rag out for another one and cool the part, then do two more, (for a total of 4ea 2-3 fusion puddles 90* apart). You "dive in" quick, apply a lot of power to get the wet out as soon as you can, then get it out of there. If the fusion weld cracks, you may need to use a little bit of fine SS rod.
Unless your crank pin has oblonged it's hole, it shouldn't pull enough to hurt anything. If it has, maybe braze it with some low temp stuff, or take it somewhere where you and a friend could hit it with two TIG welders at the same time. We've done that here in our shop when it's been something critical. Lastly, you can also TIG with brazing rod, it allows you to focus and minimize the heat. Again, dive in, apply a lot of power to get wet out, then get it out of there. It's worth practicing on a piece of scrap to get the settings right.

I've fixed (temporarily and permanently) a lot of stuff this way, where I have to keep heat down due to not melting seals, keeping a pulley running true, etc.
Thanks for the info! I'll look into welding the pins. None of the holes are oblong now so now is the best time to nip this in the bud and prevent further issues down the road. I figure its only a matter of time before the joints get loose again.
What youre saying makes sense, but its the exact opposite of what I was thinking. I was thinking low amperage to keep the heat low and help prevent warping, but I can see how a quick higher amperage tack would do well too. Get a puddle formed quick without heating the surrounding metal too much. I have the pieces of my last crank shaft in one of my scrap buckets so I can pull some of that back out to practice on.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
Posts: 409
Joined: Tue Aug 22, 2017 10:33 am

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Tue Jan 16, 2018 12:22 pm

Exactly!
The first years I started welding, I was always cautious with applying heat and then by the end of the weld the part would get too hot sometimes because I was heating the part too long. Once I got more confident, I ran the amperage as hot as the torch will take to get the puddle started ASAP, then move faster, apply filler faster, and if needed, back off on the pedal as I progressed along the seam( in the instance of a long weld).
This also works well when you've got a lap seam(non-pressure vessel only!) that is growing a pourous "volcano" at the end of the weld as it tries to seal off the slight amount of air trapped in the joint. Let the part cool, grind it out, then hop in real quick and get a nice hot tack in there. It will seal and cool before the air has a chance to bubble up again.

Soot n' Cinders
Posts: 654
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 12:47 pm

I’m definitely going to hang on to this info!
My machine is good for 180 amps so it sounds like I should give the crankshaft a quick burst of 180 amp to tack it in good. Doesn’t need to be a super strong weld but I don’t want to have to fix the crank a third time
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

User avatar
NP317
Posts: 977
Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon

Re: Building the 2.5" Scale Shay

Post by NP317 » Tue Jan 16, 2018 9:01 pm

Also consider using a modern wicking super-glue to secure the shafts. Perhaps green LocTite?
I'm sure there are better products than the Green L.
Just make sure to flush out all oils prior to application, perhaps using brake cleaner.
Other ideas?
~RN

Soot n' Cinders
Posts: 654
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 10:28 pm

NP317 wrote:
Tue Jan 16, 2018 9:01 pm
Also consider using a modern wicking super-glue to secure the shafts. Perhaps green LocTite?
I'm sure there are better products than the Green L.
Just make sure to flush out all oils prior to application, perhaps using brake cleaner.
Other ideas?
~RN
Im a little dubious of using loctite on the crankshaft. Its one thing for wheels on axles but theres a lot of torque passing through the crank.
And at this point I've got it fixed permanently. I follow rkcarguy's tips and did four quick tacks at 180 amps and the shaft is still within tolerance and its more than strong enough now, I couldnt get my test piece apart with my 20 ton shop press. But of course in the process of taking the crank out and apart to weld it I knocked the timing out again. Probably another 30-60 minutes of work to get everything dialed back in.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

rkcarguy
Posts: 409
Joined: Tue Aug 22, 2017 10:33 am

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Tue Jan 16, 2018 10:28 pm

Green Loctite "sleeve retainer" might work, but once that is in there, there will be no welding unless it's pressed apart and well cleaned. On top of that, with something reciprocating, there is no guarantee it will hold. I've had good look using it for stationary items...live a sleeve for example lol.
I'm of the thought that it could be TIG welded with care, and stay within a couple thousandths or better if you take your time and keep heat minimal.

rkcarguy
Posts: 409
Joined: Tue Aug 22, 2017 10:33 am

Re: Building the 2.5" Scale Shay

Post by rkcarguy » Tue Jan 16, 2018 10:29 pm

Im a little dubious of using loctite on the crankshaft. Its one thing for wheels on axles but theres a lot of torque passing through the crank.
And at this point I've got it fixed permanently. I follow rkcarguy's tips and did four quick tacks at 180 amps and the shaft is still within tolerance and its more than strong enough now, I couldnt get my test piece apart with my 20 ton shop press. But of course in the process of taking the crank out and apart to weld it I knocked the timing out again. Probably another 30-60 minutes of work to get everything dialed back in.
Glad it worked!

Pontiacguy1
Posts: 752
Joined: Thu Apr 26, 2012 10:15 am
Location: Tennessee, USA

Re: Building the 2.5" Scale Shay

Post by Pontiacguy1 » Wed Jan 17, 2018 9:28 am

One thing about loctite... Brake parts cleaner will leave a slight residue. If you want to clean parts good for loctiting them together, use carb and choke cleaner. The major active ingredient in carb and choke cleaner is acetone, and the loctite cleaner/activator that you can buy is also mostly acetone. If you do your final cleaning with carb/choke cleaner, you should have no problems getting it to stick.

User avatar
NP317
Posts: 977
Joined: Tue Jun 24, 2014 2:57 pm
Location: Northern Oregon

Re: Building the 2.5" Scale Shay

Post by NP317 » Wed Jan 17, 2018 12:04 pm

I'm pleased to hear that your Quick Weld worked. Yea! Remember to have fun re-timing the eccentrics.
And Thanks to Pontiacguy1 for the added knowledge for LocTite pre-cleaning.
Folks on this Board Rock!
~RN

Soot n' Cinders
Posts: 654
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 17, 2018 9:48 pm

NP317 wrote:
Wed Jan 17, 2018 12:04 pm
I'm pleased to hear that your Quick Weld worked. Yea! Remember to have fun re-timing the eccentrics.
And Thanks to Pontiacguy1 for the added knowledge for LocTite pre-cleaning.
Folks on this Board Rock!
~RN
I did have fun, timing stephensons valve gear can be an interesting thought experiment. And I agree, folks on this board rock. So much experience in one place.

Anyway, with Atlanta shut down for the snow I had a great day in the shop. Came up with a design for and then built two snifters for the shay.
0138afbbd050580358dc77e2728eda8da0a6880c63.jpg
017699721ffe639fc92346a58fa4eda116b52dd31f.jpg
Its a simple 3 piece design with a regular poppet valve inside, the little stem sticking up is connected to the poppet so it indicates where the valve is. It can also be used to knock the valve open if it gets stuck. They close with a puff and a snap and then open up as soon as pressure is removed. Surprising how loud they are but makes sense. With no spring inside, they should wisp steam with the throttle barely cracked, just like the big ones.
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

Soot n' Cinders
Posts: 654
Joined: Wed Jun 27, 2012 5:24 pm
Location: Marietta, Georgia

Re: Building the 2.5" Scale Shay

Post by Soot n' Cinders » Wed Feb 07, 2018 12:17 am

Time for another update! The delivery and exhaust lines are complete and work on the smokebox door is underway.
01a81a204d547257e82ef0e6cb1b60c248a11ad21e.jpg
01698ccc4f8fab94ebda7c9e7478618d000c0528ca.jpg
-Tristan

Projects
-2.5" scale Class A 20 Ton Shay

Post Reply