Stephenson's Rocket

[Brian Rupnow]

Words alone can not express how much work went into these eccentrics. I still need to make the eccentric retainer plate that bolts to one side of each eccentric to keep the eccentric straps in place, but I will save that for tomorrow.

[Brian Rupnow]

This morning I got up and made the eccentric strap retaining plates (for the second time) and bolted them to the eccentrics. All looks good---I am going to turn a few thou off the heads of the #4 shcs to clear the shaft better (they are mounted to a dummy shaft in the picture).I'm not certain that it shows in the picture, but there is a #5 set screw in the hub area of each eccentric, which fixes them to the shaft.

[Brian Rupnow]

This picture shows the eccentrics with the eccentric strap retaining plates bolted on, setting in place on the drive axle. You can see the cut away portion of the axle mounting plate that is clearance for the eccentric strap as the axle rotates.  I went by Princess Auto today to buy some oilite bronze bushings to press into place in the axle mounting plate, but the people were lined up all the way around the building, keeping their 6 foot distance apart for Covid. I didn't bother stopping--I'll either make my own bushings or figure something else out.

[Brian Rupnow]

And today, I whittled out eccentric straps. Not difficult, but time consuming. There are actually two or three  ways to do eccentrics. The way I have done with two piece bolt together eccentrics and one piece eccentric straps, or you can do one piece eccentrics and two piece eccentric straps. I don't know which is easiest. I've made them both ways, and it ends up being about the same amount of work.

<a href="https://www.youtube.com/watch?v=A5vFaNjReWc" target="_blank">http://www.youtube.com/watch?v=A5vFaNjReWc</a>

[Admiral_dk]

It's been mentioned many times by others, but it's usually the fidly bits that takes the longest times .... but you are making good progress none the less Brian.

[AlexS]

Hello Brain,

I like the way you build it symmetric.
For making the eccentric, which turning tool did you use to cut (rough cut)? Didn't make a eccentric or one piece crankshaft before

I also find this on the web. Something for the next project? 

<a href="https://www.youtube.com/watch?v=XmmutEViK7Y" target="_blank">http://www.youtube.com/watch?v=XmmutEViK7Y</a>

[Brian Rupnow]

This morning I put on my mask, stood in line, and bought four oilite bronze bushings that were 3/8" i.d. x 1/2" o.d. ---This afternoon I determined that there is no way in Hell that you can turn the outside diameter down to 7/16". Doesn't matter how sharp the cutting tool is, doesn't matter what speed you run the lathe at.--The bushings crumble before you can get them down to a 1/32" wall thickness. They were the only bushings available locally. Pooop!!!

[crueby]

Never tried oilite, I have used bearing bronze, 932 or sometimes 660 I think, with good results. Its available in a number of diameter bars, cuts great.

[Brian Rupnow]

Alex--The eccentrics were turned using brazed carbide tools. The brass eccentric straps were made from 3/8" brass plate. The center hole was drilled and reamed, the radii were drilled thru the plate, and the o.d. was rough sawn to shape on the bandsaw and then mounted on my rotary table to finish the o.d.

[Brian Rupnow]

I have four little pivot arms for the eccentrics. They were laid out on a piece of brass plate, drilled, reamed, and rough cut on the bandsaw. On bigger pieces I generally go right from the bandsaw to my vertical belt sanding machine and finish them off "by eye". I can't do that on pieces this small, so they will be machine finished using my milling machine and rotary table. I will have to make up some simple fixturing to hold them, and will post pictures of "in process" work.

[Brian Rupnow]

The pivot arms are completely finished (I think the wide ones get a slot added yet). These were too small for me to hand finish "by eye", so I made up a mandrel with a 7/16" diameter register on the end of it, over which the levers would fit (they are 7/16" reamed hole). The o.d. of the lever bodies is 11/16" diameter, the outside diameter of the fixture is 5/8". The flat head capscrew is 0.493" diameter, so it will not pass thru the bore on the brass bits. When the capscrew is cinched down tight, it captures the brass bit so it can not rotate. It is then a simple matter to hold the fixture in the 3 jaw chuck on my rotary table, set up the appropriate offsets, then turn the handle on the rotary table to spin the chuck around, while the endmill cuts with it's side to finish off the o.d. of the brass pieces.

[steamboatmodel]

This morning I put on my mask, stood in line, and bought four oilite bronze bushings that were 3/8" i.d. x 1/2" o.d. ---This afternoon I determined that there is no way in Hell that you can turn the outside diameter down to 7/16". Doesn't matter how sharp the cutting tool is, doesn't matter what speed you run the lathe at.--The bushings crumble before you can get them down to a 1/32" wall thickness. They were the only bushings available locally. Pooop!!!

Oilite bearing are made from a powder sintered in a mold and can not be machined, you are stuck with stock sizes.
Gerald. 

[Jasonb]

They can be machined but the makers say very sharp tools, they don't like reaming as that closes up the pores. I have had no problem cutting with CCGT inserts though I did not go down to 1/32" wall which may have been too thing and what gave Brian problems though more likely low top rake on the brazed carbide tools he was using.

https://oilite.com/Best-Machining-Practices

[Elam Works]

Yup, I have machined Oilite. Plenty of bushings and thrust washers where I needed a non-standard size. Sharp tool to avoid smearing, no problem. Usually use HSS rather than carbide so I can grind a sharper edge. Also, unlike regular bronze, positive rake rather than a neutral rake to help with shearing rather than plowing the material out of the way. Because the material tends to crumble and break up into small chips, you think it is turning great regardless of what the cutting edge is like. But check the surface with an eye lop to see if you are really cutting it or smearing it.

-Doug

[Brian Rupnow]

Today we move a little farther towards a running engine. The eccentric pivot levers (for lack of a better thing to call them) are finished and in place on the engine. I still have to make up a few connecting links and rod ends, and figure out what to use for a flywheel, but it's getting close to "run time".