Author Topic: Chris's Marion 91 Steam Shovel  (Read 305853 times)

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3525 on: March 27, 2019, 04:36:55 PM »
You forgot the radio control and CCTV so the elves don't have to go out in the heat/cold to run this beast.

Don
They should still have their parkas from when we all worked for the big guy up north.  :Lol:

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3526 on: March 27, 2019, 08:04:45 PM »
Making up the front arms for the eccentric followers - round rod with a fitting on the end to take the pivot pin from the lever which takes the motion up to the valve rod on top of the engine. The fittings are just a square bar with a small hole drilled in - as usual when making a series of small parts, left them as a long bar to drill all the holes:

Then chucked in 4-jaw on the lathe to drill the end hole and part the off one at a time:

And used some loctite retaining compound on the rods to glue on the fittings - will let those set up, then cut the rods to length and loctite them into the followers. I want the length of each rod so that at middle of the stroke the pivot hole is directly under the pivot point of the lever.

From here out, most of the parts remaining are small fiddly-bits, except for the pistons which are just small-ish.

Offline gary.a.ayres

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Re: Chris's Marion 91 Steam Shovel
« Reply #3527 on: March 28, 2019, 06:41:53 AM »
Always interesting to see how you do things.

 :ThumbsUp:

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3528 on: March 28, 2019, 01:55:23 PM »
Last night I got the rods trimmed to length and loctited into the followers. The inside edges of the end pieces were filed back to the edge of the rods so there would not be any chance of the crossheads snagging them on the way past.

The cranks were all assembled:

and I am getting them fit into the engine blocks. There are a few places that needed a little filing for clearance, first one is together and moving freely:

You can see in the slot where the eccentric rod comes up - it will connect to a lever in the bearing on top and another lever will move the valve rods up in the steam chest.
A view from the end:

An awful lot of stuff in a 2" wide block!

Offline cnr6400

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Re: Chris's Marion 91 Steam Shovel
« Reply #3529 on: March 28, 2019, 02:24:06 PM »
VERY tight spacing for the rotating assembly! Looks great - terrific progress.  :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Just a thought re eccentric straps - how confident are you about the loctite bond from the round rod to the eccentric strap and the end blocks? I'm just thinking that if a joint or joints ever let go it may be a heck of a job to get to them to repair them. Could the eccentric arms be made from flat stock and pinned / silver soldered to the eccentric follower plates in the tapered area? Small pivot hole in end could be jig-drilled at exact centres to the large hole after soldering. The strap link would be be just as thin as the rod and block, and it would have very strong joints. Hate to suggest back-tracking, but may be worthwhile. Just food for thought.
« Last Edit: March 28, 2019, 02:34:35 PM by cnr6400 »

Offline ddmckee54

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Re: Chris's Marion 91 Steam Shovel
« Reply #3530 on: March 28, 2019, 06:13:09 PM »
I'm with cnr6400 on this one.  Normally you would only be concerned about the shear strength of the Loctite - at least I think it's shear strength.  When you open up the side of the part you need to be looking at the peel strength more than the shear strength.  I'm not sure, but I don't think Loctite is that great for peel strength.

It might hold for 50 years, or it might let go the first time you put steam to it.  Have the elves silver solder those suckers and don't worry about them anymore.  Or don't you trust the elves with a torch?

Don

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3531 on: March 28, 2019, 06:25:03 PM »
Those rods go .350" into the followers, and .225" into the end fittings. The side that was filed down is only 1/4 of the way to the center of the hole, so still lots of the hole holding it, on 3/4 of the circle. It cannot peel off to the other side, and the retaining compound seems pretty strong on these joints, I think they are fine. If I am wrong, its just a matter of unscrewing the base cap to pull the follower, the crank can stay in place. They could be silver soldered in place if needed, but I don't want to change the shapes, they match the real one.

Offline RonGinger

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Re: Chris's Marion 91 Steam Shovel
« Reply #3532 on: March 29, 2019, 02:15:42 AM »
I just went back and looked at post 3245, the CAD drawing of the engine. I see that each side has a crank that drives a shaft in the three bearings on top of the engine, then a second crank drives the slide valve. That shaft must be split in the center journal? You cant have each end of the shaft being rocked by the eccentric on that cylinder. What holds that rocker shaft to keep it sliding out of the bearings?

What am I missing?

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3533 on: March 29, 2019, 11:46:07 AM »
I just went back and looked at post 3245, the CAD drawing of the engine. I see that each side has a crank that drives a shaft in the three bearings on top of the engine, then a second crank drives the slide valve. That shaft must be split in the center journal? You cant have each end of the shaft being rocked by the eccentric on that cylinder. What holds that rocker shaft to keep it sliding out of the bearings?

What am I missing?
You are right Ron, that rod is split in the middle bearing. They really didnt need that center one, but I think they had it to keep the rod from twisting in one narrow bearing. The levers on either side of the bearing keep it from shifting to the side. That render was done from an early design, I had the lever on one side in the wrong place, fixed that later on.

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3534 on: March 29, 2019, 01:05:32 PM »
Ron, here is a newer screen capture of how the levers/rod look after I corrected the position a while back. The center cap is removed to show the split in the rod - it is hard to tell on the original engine, given all the dirt/grease on it, and without dismantling (which I am not allowed to do, obviously), exactly where the joins were. It is possible that they had a center rod down the whole length, or did it like I did with a split in the center and just a socket joint there, lots of ways they could have done it.

This does show how the bearing caps keep the levers from shifting sideways though.
Chris

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3535 on: March 29, 2019, 06:05:57 PM »
Not much shop time yesterday, back in today, and got the other two engines fettled and assembled, all are turning over nicely now after easing a few binding spots at the end of the broached recess in the side. I think I'll go back and make the piston rod glands in the cylinder bottom plates next, then the piston rods/pistons, and work my way up to the valves from there....
 :cheers:

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3536 on: March 30, 2019, 12:56:30 AM »
Got the piston rod glands started - centered the bottom caps in the mill on the holes drilled back when they were made, and counter drilled to fit the o-rings. Used a regular twist drill, which leaves the bottom of the hole a cone which helps compress in the o-ring as the gland is tightened.

Did all three of the caps, then started turning down the gland caps. These are drilled to match the cap holes, and turned to fit the counter drilled holes closely. The small end is long enough to reach down to the o-ring and leave another .025" or so to have compression room, which is plenty, they wont be tightened down all the way, just enough to seal.

Made up two for each engine:

Next time will drill/tap for the screws to tighten them in with....




Offline Captain Jerry

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Re: Chris's Marion 91 Steam Shovel
« Reply #3537 on: March 30, 2019, 12:54:59 PM »
Chris, I am following along and enjoying the fine detail of your project and your methods.  Looking at the valve linkage and the pivoting rods on top of the crosshead guide, they seem to be crying out for some Zerk fittings.


Jerry
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Offline crueby

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Re: Chris's Marion 91 Steam Shovel
« Reply #3538 on: March 30, 2019, 01:11:24 PM »
Chris, I am following along and enjoying the fine detail of your project and your methods.  Looking at the valve linkage and the pivoting rods on top of the crosshead guide, they seem to be crying out for some Zerk fittings.


Jerry
Yup, the originals had oil cups and grease points, but on this scale that would be tough since the followers are so thin. Maybe some dummy ones... A drop of light oil on the joints does wick in well.

Offline cnr6400

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Re: Chris's Marion 91 Steam Shovel
« Reply #3539 on: March 30, 2019, 06:46:56 PM »
Is it true that one piston or valve gland in the hand is worth four on the floor ?

(sorry, I'll get my coat on the way out.....forgot to issue the bad pun alert)