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[Johno]

As your build is based upon the Stuart's D10 and as such all original dimensions are imperial. Stuart's are the oldest steam model engine makers in the world and to the best of my knowledge have never used the metric system.

http://www.stuartmodels.com/

[Stuart]

No problems Brian

I posted for info for you and others who may nee the SS some Ali bronze

[Stuart]

Johno

Yes but my namesake company has changed hands many times in the past and things are not as good as in the past still ok but not as good

Now it’s not my company nor have I any affiliation with them but I am a customer

[Brian Rupnow]

I'm sure that if 100 engineers/machinists were asked "How do you turn that round bit on either side of the rectangular bearings?" you would probably get 100 different answers that all work. This is what works for me. I machine the bearing blocks to finished size on the outside, put the appropriate bolt holes in, and ream the bore to 1/32" undersize. Then I turn up a short piece of round bar that is a snug fit in the bearing block, coat the round rod with Loctite 638 and assemble as you see them. For the two outside bearings which have 1/16" oil holes in one side, I drilled 1/16" thru the bearing and thru the round rod so that I can Loctite a short piece of 1/16" crs rod thru both bearing and shaft because the cuts taken in the lathe will be interrupted cuts and I wanted the extra insurance that the bearing wouldn't break free from the round rod while I was turning them. The center bearing has an oil hole also, but when I made the two halves I drilled a clearance hole on one half and a #5 threaded hole in the other half, so it will put enough "squeeze" on the stubby shaft that I'm not concerned about it breaking free from the shaft while turning it.

[crueby]

Good way to turn them. Will you be taking the holes to final size after mounting in the base?

[Brian Rupnow]

That's the question, isn't it. What I would like to do, is assemble the bearings into the base, lock everything down, and then drill and ream them to final size "in assembly". That is the way to do it on bushings with a larger bore, but on little stuff like this where there is no possibility of running a boring bar thru everything in one set-up, I have to make it up as I go along.

[crueby]

..., I have to make it up as I go along.

Thats the really fun part!

[Brian Rupnow]

So, very carefully the bushings are turned on their stub mandrels and fitted to the aluminum base. The bushings are all currently reamed to 0.281" during this first operation. A bit of experimenting shows that a 0.281" reamer will pass thru all three bushings after they are installed in the base without wanting to take any large amount of bronze of any of the three bushings, which is very encouraging. The next stunt is to take my 0.311" reamer and take a complete pass thru all of the bushings with it, watching very closely to make sure that the reamer is not being pulled "out of position" by any radically "out of alignment" holes. This seemed to go very well, so now I move up to the final size 0.3125" reamer and slowly run it thru all three bushings. Now for the big test---does a 0.3125" shaft fit thru all three bushings?  This is not guaranteed, because if any one bushing was too far out of alignment, the reamer would be quite happy to follow the out of alignment hole. Reamers will not straighten or "true up" a misaligned hole. They are more flexible than you would ever believe.  Luck was with me!! A 5/16" shaft does fit thru all three bushings.--a bit reluctantly, but only a bit, and it can be turned when in place. Before I go any farther with things now, I will mount the base to my work-bench, put an 8" v-pulley on the shaft, and after a liberal application of oil I will drive the shaft for an hour with my old half horsepower bale elevator motor. this will take any "stickiness" out of the bushings and should let a shaft rotate very freely, which is what I am aiming for.

[Ye-Ole Steam Dude]

That is some very fine machining Brian.

Thomas

[Brian Rupnow]

Here we are "running in" the new bronze bushings. I bought that motor from a farmer for $10 about 10 years ago for a replacement motor on my big power hacksaw. Turned out it was only a stuck brush on the big hacksaw motor, so I have kept my red 1/2 HP motor for a "spare". The 8" pulley originally had a 3/4" bore, but I have made up a collection of split bushings so I can run it on 1/4", 5/16", 3/8", and 1/2" shafts. The pulley on the 1750 rpm motor is a 2" diameter, so the crankshaft is turning at about 440 rpm, which seems to be about right for running in bushings. Any faster and it burns them and they end up too sloppy, any slower and it takes too long to get the job done.

[crueby]

Do you use any compound like Timesavers, or just let the metal itself wear in?

[Brian Rupnow]

I just let the material itself wear in. If you look at anything which has been machined by reaming or drilling or boring under high magnification, the surface will look a lot like the rocky mountains. All the "running in" does it knock the highest peaks of the mountains. In extreme cases I have used a bit of 600 grit lapping compound, but I try and stay away from that.--Just use cutting oil instead of lubricating oil.

[Brian Rupnow]

Chris--I have to revise my last statement. After the motor ran for half an hour the crankshaft bushings were much looser---but not loose enough. These little steam engines really don't like any resistance in the crankshaft bushings at all.---So--I switched out the short piece of 5/16" shaft with the pulley on it for a piece about 12" long, coated it with 600 grit carborundum paste, and using the pulley somewhat like a steering wheel I pushed the shaft thru all 3 bushings with a twisting in and out motion for a couple of minutes, making sure at all times that the shaft was engaged with all 3 bushings. (It wouldn't do much good if it was just a rotating movement--that would give annular grooves around the inside of the bushing.) Pushing the shaft in and out and turning it at the same time very quickly cut a couple of tenths off the inside of the bushings. After cleaning up everything in a varsol bath and blowing thru the bushings with compressed air, I reassembled the short shaft with a bit of lubricating oil, and it spins very freely.

[Brian Rupnow]

Next up will be the crankshaft. In the original plans, the crankshaft and rod journals were 0.281" (9/32") diameter, but I am blowing that up to 0.3125" (5/16) because I have reamers to suit that. The original plate crank-throws were .156" thick, but I am going to use 3/16" material, because I want the added thickness to help hold the pressed together parts more securely. I don't anticipate a problem making all the individual components, but getting everything pressed together and still maintaining the alignment required may be a challenge. The cold rolled shafting I have measures at 0.3120 to 0.3125" diameter. My undersize reamer is supposed to make a hole 0.3110" diameter. Probably a .001" press fit will work okay, as these steam/air powered engines are not high revving engines and not torque monsters.

[Brian Rupnow]

This is how I plan on going about the pressed together crankshaft. The grey 3/16" plates are the crankshaft "throws". The blue shaft is a "sliding fit" through these two plates and it's only purpose is to keep the two center holes in the plates perfectly aligned. The red round shaft will be the con-rod journal, and it will be a "hard press fit with Loctite" into the two grey plates. The green part is a temporary spacer which will be an exact fit between the two grey plates, probably held in place with some hot glue from my glue gun. The purpose of the green spacer is to prevent any movement of the grey plates relative to the red con rod throw and each other, when I press the long portion of the main crankshaft through everything--a hard press fit. once the crankshaft is fully assembled, I will heat and remove the green spacer plate, and mill away the remaining piece of the long main crankshaft from between the two sets of "throw plates"