Stephenson's Rocket

[Brian Rupnow]

I spent a couple of hours chasing down "tight spots" in the system this afternoon. That is done basically by process of elimination.--Keep taking parts off one at a time until the main shaft rotates freely--open up clearances on the offending part, put it back on, then repeat. Eventually you get to a point where the main shaft rotates without any binding.--The result?---An engine set that runs consistently at 20 psi. There will be no more posts now, until I start fabricating the chassis which the engines bolt to.
<a href="https://www.youtube.com/watch?v=CtDl6fQFLC4" target="_blank">http://www.youtube.com/watch?v=CtDl6fQFLC4</a>

[Art K]

Runs great Brian!
Art

[Brian Rupnow]

And here we have the rest of the material to build the chassis with.---Except for the big drive-wheels. If you are wondering, that's $97 worth of aluminum setting on the chair. I enjoyed a machining free morning. When I designed the chassis, I just thru in all the shapes with no real attention paid to how they all go together. This morning I started "finessing" all of the parts to add in the threads, bolt holes, etcetera.

[Brian Rupnow]

Where to begin, Where to begin??? I think the simplest part is going to be the smoke-stack.---And no, I haven't got the faintest idea of how to make that frilly part that fits on top of the stack. I think to look right, I'm really going to have to make it, but I haven't got a clue as to how.

[Jasonb]

Unwrap it in your CAD program so it is flat sheet then print it out to use as a template then saw and file some sheet metal before rolling it back up and soldering into a ring.

Alternative would be to run a gig say 10dp gear cutter across the end of a bar at say 12 divisions then bore out the middle and bend what is left outwards to a trumpet shape.

[crueby]

Unwrap it in your CAD program so it is flat sheet then print it out to use as a template then saw and file some sheet metal before rolling it back up and soldering into a ring.

Alternative would be to run a gig say 10dp gear cutter across the end of a bar at say 12 divisions then bore out the middle and bend what is left outwards to a trumpet shape.

Making it out of sheet and rolling it sounds like a great plan, probably how the original was done too, minus the cad design step!

[Brian Rupnow]

And yes, my darlings--We have a smokestack!! Turned and drilled from 1 1/2" solid.  By the time I was finished the swarf in my tiny shop was knee deep.

[Art K]

Yup, I can picture the knee deep swarf from here.
Art

[Brian Rupnow]

This is where I am going now. An "exploded" view gives some pretty good insight of what lays ahead with the chassis build. the engine assemblies don't appear here.

[Brian Rupnow]

Today's entertainment was end-plates for the boiler. There is nothing really special here, just a lot of machining. If you have a good eye you will see that one endplate only has two holes, as opposed to having three holes as shown in the exploded view. As I was about to drill the third hole in the second plate, I thought "Jeez, I'm not lifting elephants with this thing---2 holes will be enough." One endplate will support the smoke-stack and the other is bolted to the fire-box. The bolt heads will be on the inside where nobody will see them---so---clearance holes in the endplates, threads in the fire-box and smoke-stack support. You will also see that the design evolves as I make the parts. The end plates in the model were a lot of mass for no good reason. I relieved a lot of the center of each endplate, and then went in and modified the drawings.

[Brian Rupnow]

This morning yielded a fire box. I decided to carve out most of the interior to make it a lot lighter, and I made it round so I can fit a nice fire box door. The only problem with buying off-cuts at my metal supplier is that sometimes trimming the off-cut down to the size needed to make the part is more work than making the part.

[Brian Rupnow]

Does anyone know where I can buy this? I've seen them before but I can't remember where. They are basically a small diameter tube (or even solid would do) about 5/16" to 3/8" diameter formed into a continuous circle about 1 1/2" diameter. Model builders cut portions of them away from the circle to use as elbows in model piping.---Brian

[Jasonb]

"360 degree Mandrel bend donut"

though I have not seen them in the sizes you mention, usually bigger for exhaust fabrication etc

Not to hard to make solid ones yourself, either turn on the lathe  or wrap rod around a larger one like a spring, cut off one turn and then flatten.

[Brian Rupnow]

thanks Jason---It was only while I was making the post that I thought "Huh---It is only for show--Probably I could make it from solid."

[Brian Rupnow]

Today I finished the assembly of the front portion of the chassis , including the front plate itself, a 1/8" spacer, the crazy smokestack support and the smokestack. That smokestack support is a monster. It required three different fixtures to machine that part. I could have designed it simpler, but I wanted to attempt all of the fixturing. I will post the finished assembly and the three fixtures required to machine the support.---I got lucky with the third set-up and was able to use the front plate as the holding fixture for the third machining operation.