Another Corliss Engine

[vcutajar]

Jerry

I am going to set this engine up to run under

If it's not too complicated to explain, could you tell me how you will achieve that?

Vince

[Captain Jerry]

Vince it is very complicated so I will only have space to give you a simplified version of the full explanation. 

       Rotate the eccentric 180°

For those who may not understand what is meant by running "over" or "under", it refers to the direction of the connecting rod and crank on the outward stroke of the engine.  It is the same as forward and reverse but it better defines which direction is forward.

Jerry

[Captain Jerry]

I was going to post this with the previous but I was called to dinner. My grand daughter is home from college after a week in Ft Lauderdale for spring break.  She had three of her schoolmates with her so it was a great dinner.

Here is the girder frame Corliss that was my inspiration for this engine. I did not attempt to model it to any detail since this video is the only view that I have.  It is running "under."

http://www.youtube.com/watch?v=Nzv9lOFIHMo

More to follow.

Jerry

[zeeprogrammer]

Very nice video. Thanks for posting that. Probably one of the best I've seen.
I also appreciate knowing about 'over'/'under'. I'd never thought about that.

[Alan Haisley]

That is a beautiful machine, Jerry. I really like the telescoping oiler tubes.
Alan

[Captain Jerry]

Today was one of those frustrating days that happen once in a while.  I spent much of it chasing my tail because of cloudy thinking.  The problem was a slight binding when rotating the shaft in the above trial assembly.  I convinced myself that the problem was with the crank pin not being parallel to the shaft.  This crank pin is threaded into the crank web and it is the first time that I have used this method.  I had drilled for the shaft and the pin in the same setup so the holes should be parallel and I had tapped the hole for the pin #10-32 in the same setup so I was more confident of the web than I was of the pin.  The pin is 1/4" drill rod turned and finished to .218" for the body of the pivot  and the end was turned to .185" before threading with a #10-32 die held in a die stock and kept square to the pin with the face of the tailstock chuck.  A thread runout was turned next to the shoulder so that the shoulder would bear against the face of the web.  The pin was parted of leaving a head to retain the con-rod with space for a washer. 

I was so sure that the pin was somehow not square or parallel to the shaft that I remade the pin.  No improvement.

The next thing that got my attention was the con rod.  If the holes for the crank pin and the hole for the cross head pivot pin are not parallel it could cause binding.  I spent (wasted) a lot of time checking this before being satisfied that the con rod is straight and that the holes are parallel.

The only thing left was the cross head.  It should have been obvious and maybe it was but I didn't see it.  The hole is square through the cross head shoe BUT the threaded end of the piston rod was bent out of line where it joined the cross head which caused the hole to not be square with the guide bore.  Crap!

Tomorrow, I will make a new piston rod.  I may make a new cross head.

I should have done a better job of analyzing the problem and the fix would be done by now.

Jerry

[Captain Jerry]

Big progress today!

I have given up trying to find 7" steel pipe for the flywheel.  Although it is defined in the pipe schedule 40,  7" seems to be rarely used, so I have the choice of 6" or 8" schedule 40 steel pipe for my flywheel rim.  To my eye, the 8" is just too big and causes some clearance problems so I have decided to go with 6" pipe which has a 6 1/4" OD with a wall thickness of .28".  Today I ordered 2 pieces.  On piece is 1" and the other is 1.5" wide.  I would like to use the 1.5" width with two sets of spokes, just for fun, but no decision has been made.  The 6" pipe is still beyond the capacity of my chuck but I have a plan.  When I have the pipe in hand I will see if the plan fits.

Jerry

PS:  Update on my great granddaughters interest.  She has engineering in her, that's for certain, but she hasn't settled on her field yet. She really likes my shop and tools and I thought she was headed for a mechanical field, but today she decided to investigate civil engineering with an emphasis on ground water management.



Fine with me.  Bulldozers and excavators are as fun toys too.

[ths]

I understand her need to do that sort of thing.

Hugh.

[zeeprogrammer]

Good career choice. She'll be in high demand.

[Captain Jerry]

I have been doing the amateur machinist two-step for the past week with emphasis on the "two steps back." But after making new piston rod and cross head and fork end fitting for the connecting rod,  I have finally caught up with myself.  Just in time!  My flywheel rims have arrived:



That is two pieces of 6" pipe ( can't find any 7") one of which is 1" wide and the other one is 1.5" wide.  I won't get to them for a few days but I have a plan.  The pipe was cut with a bandsaw so it wasn't hardened by an abrasive wheel.  Those weld spots look like they might be a little hard though.

Jerry

[Captain Jerry]

 

I keep looking at the two pieces of pipe above and thinking wondering if I could get one of them to fit inside the other.  They are the same size now but if I were to take a section out of the 1" slice, could I squeeze it into the other one?   The circumference of the OD is about .8" greater than the ID so if I were to cut out a .8" section it should fit but I don't know how hard it would be to compress the circle after I cut it.  The thickness of the rim is about .28"

Jerry

[vcutajar]

Jerry, just my thoughts.  If you manage to compress the ring with the cut section, I suspect it will become oval.

Vince

[Maryak]

Jerry, just my thoughts.  If you manage to compress the ring with the cut section, I suspect it will become oval.

Vince

You may be able to overcome this tendency if you use say 3 large jubilee clips, sort of like a poor mans ring compressor.

Best Regards
Bob

[Captain Jerry]

Thanks for the input, Vince and Bob.  I've been thinking about it some more.

After cutting out a section. the part looks like a letter "C".   If the closing force is applied top and bottom, all of the bending force is applied to the left side between the point of contact at top and bottom.  The left side will bend uniformly but the right side will not bend at all because there is no force applied to it.  The gap will close but the sections will retain their radii.   Not quite an oval but surely not a circle.  The problem is where the clamping force is applied.

Jubilee clips are a good thought, Bob.  They apply the force uniformly.  As long as the elastic limit of the steel pipe is not exceeded, the bending should be uniform.  If the barrels of the clips are arranged across the gap in the pipe, there is no friction between the strap and the pipe surface, and the force is tangential to the pipe surface. but I wonder if they provide enough force to close the gap.  I don't know much force it would take.

As an extension to that thought, I could make a jubilee clip out of a 1/8" x 5/8" steel strap with tabs bent outwards and closed with a bolt. I ought to be able to get enough force from that.

I haven't decided to try it yet but if I do, the cut out section will take out the weld joint in the pipe so the remaining  material is uniform.

What do you think?                                                                                                                                                  1032

Jerry

[Alan Haisley]

Jerry,
I think that a band clamp will only close the C. With a uniform tangential force applied, the material will move where the resistance is minimum - the gap will close. What you would need would be uniform radial force and I don't see that coming from a band clamp. If you have a shop press, you may be able to close it with a band and then get it round with the press.
Alan