Walking Beam Steam Engine

[Dataporter]

Hi Mark,

I use graphite valve packing string.. I use it for the "piston rings" too. Does the o-ring slide effortlessly up and down the cylinder and the ports kind of huff and puff when you move the piston up and down?
You might be able to find the packing in your local hardware store. It looks like this

http://www.ebay.com/itm/LIVE-STEAM-...581457?pt=Model_RR_Trains&hash=item58ae21eed1
or this
http://www.ebay.com/itm/LIVE-STEAM-...002179?pt=Model_RR_Trains&hash=item1c3eb2fe43
this seller used to have some string that I really like, but I don't see it today. I may connect him.

I just about have everything done on mine now. I still need to make the wood base! If I'm not totally occupied with Honey Do's, etc. I should have it running this weekend or next.

Dave

 

[Dataporter]

Oh and BTW what you do with that Grahited String is, you wrap it around something the same size as the cylinder rod 3 or 4 times, the wraps close together and just slightly tight. Then you take a real sharp knife and cut the wraps so that you end up with three or four little C or O shaped donuts. You wrap the donuts around the piston rod and drop into the hole in upper cylinder cover. Drop them in so the slits you cut in them do not line up! Then screw in the gland just finger tight or a little tighter so that string gets smashed in there good enough to seal the rod, but not so tight that it causes friction. I hope I am making myself clear! Dave

 

[mjonkman]

Thanks Dave, looks like Lowes carries the 3/32" graphite packing cord for like $2.50, though I'll probably go to ACE first since its the closest store to me but the ACE site doesn't indicate stock at my local store. I was also looking at McMaster Carr as I might need to order some stuff from them and they have square packing - 1/8" http://www.mcmaster.com/#graphite-packing/=ro2d80 - (1) General Purpose. Any advantage that you know of square over round or vice versa?

In terms of the piston using a rubber o-ring, this is my first engine so I really don't know how "stiffly" or "loosely" the piston should slide. I adjusted the o-ring groove so that the piston can be pushed and pulled up though it doesn't slide super freely. The other thing I wasn't sure of was the fit of the piston itself - what kind of tolerances should there be - I think my current piston is at about 2-3 thou under the bore size. The original popular mechanics article tells you to turn the piston down to .0002 oversized, attach the piston rod to it, chuck up the piston rod and proceed to bring the piston to its final size using a very sharp tool. That might mean something to an experienced builder but to me it would have been helpful if the article had suggested some kind of clearance size - like 1 or 2 thou undersized or perhaps even more. I don't mind remaking the piston if I need to experiment with it, as I can chalk that up to learning, but it would be helpful to have a ball park idea for these little engines.

Sincerely
Mark R. Jonkman

 

[Dataporter]

The packing cord I like is really pliable, almost like clay. You can roll it between your fingers and make it smaller, etc. The McMaster Carr #1 stuff looks good but it might be stiff, and that is a life time supply.

Friction is the enemy of your steam engine. When you have it completely assembled, you should be able to easily spin the flywheel with a child's finger. Your piston should pretty much slide down the cylinder of its own weight, particularly before you pack it. It should theoretically float down on the air it is displacing. If your piston is too small you will lose power and it won't run slowly. This walking beam is supposed to run slow so you can see the action of the links, etc. The reason you turn the last little bit on the end of the rod is for concentricity, so the rod will freely move through the gland. Also, you can shave at little, test it, shave a little, test, rinse and repeat. Use emery paper and wet or dry sand paper or a nice smooth finish. It's hard to get everything perfect, if I had to guess what the tolerance would be, I would say one or two thousandths. The trick is accurately measuring the diameter of the cylinder and no matter how hard you try, it is difficult to get a perfectly cylindrical cylinder. My motto is: If you don't like the way it runs at first, and you think it is the piston, make another one!

Dave

 

[Dataporter]

I think this is more like the string that works good for what we want to do.

"Multi-purpose self-forming graphite packing. 1/16" dia. approx. X 24" approx. long string. Soft and pliable to seal and fix all faucet packing needs...................... "

http://www.ebay.com/itm/3057-Multi-...929?pt=LH_DefaultDomain_0&hash=item3a8ed63449

 

[Dataporter]

It's ALIVE !!!

Got her running last night. This is more like a dress rehearsal. Still a few things to do before it is finished, but, it's running !!!

[video=youtube_share;CdaJdtn89Pg]http://youtu.be/CdaJdtn89Pg[/video]

 

[Rapscallion]

Looks pretty neat! Well done Dave. I've enjoyed this thread and hope that Mark meets with similar success.:goodjob2:

 

[mjonkman]

Excellent work Dave! Looks like its running really nicely. Congrats!

It will be a few weeks I guess before I can make much more progress on my engine. Stupid me went out and bought a DRO for my mill with my bonus money from last year... now unfortunately I'm stuck installing the thing Never figured it'd be such a time consuming thing to install. Started on Saturday and so far only have the x-axis scale fully installed (course I haven't been out to the garage since Sunday). The y-axis scale itself is installed on the machine but I have to make the bracket to hook the read head up to the mill table carriage (? is that correct terminology). Then I have to install and make the brackets for the z-axis. When its all installed I'll be happier then a pig in.... but until then I'm kinda stuck installing that vs. working on the engine.

On the engine side maybe you can answer one more question for me. The linkages that are supposed to be made from 1/8" ID brass tube and 3/32" rod and soldered together. Reading Rudy's instructions he mentioned making a fixture out of wood and steel pins. Which I did. Now I just naturally assumed "silver solder - aka silver brazing - 45% silver wire" but based on one attempt that ain't going to work with a wooden fixture (the fixture burned really nicely - but I had figured it would). Obviously a metal fixture is useless because the silver solder will just as easily flow onto the steel fixture and freeze the linkage to the fixture (don't ask how I know that ) I was using a regular MAPP gas torch so that thing throws a lot of heat everywhere, so I've gone out and bought myself a little butane pencil flame torch to minimize the flame and be more precise and I guess I'll just using soft solder. The only soft solder I have on hand is what I've used for sweating on copper fittings on plumbing pipes - something I'm far more adept at then using silver solder/brazing, is that the appropriate solder for this purpose or is there a better solder? I noticed that the hardware store seems to distinguish between solder for electrical purposes, solder for general purpose, lead free solder for plumbing and acid core solder for general purpose. Obviously this isn't a boiler or such so silver brazing is probably not required to join these linkage components and the excess heat seemed to warp the 3 linkages I made. Curious to what you used in making yours. Sorry for all the dumb questions - probably should spend more time researching the stuff on my own

Sincerely
Mark R. Jonkman

 

[Dataporter]

Hi Mark
You will love your DRO! It seems like cheating to me, but there ain't no other way once you use it!

I went to our local welding supply company and bought some silver solder and flux in a little kit that was pretty reasonable like $10 (silver is higher now).
It melts at only 450 degrees F. It may very well be the same as your plumbing solder, check it out. You don't want electric or rosin or acid core that's for sure.
I made a little jig from a small piece of aluminum with two 1/8" pins at the right distance on centers.
Polish or clean the the tube and 3/32 rod before you cut it so that it is bright and not covered with tarnish.
Make a couple extra pieces for obvious reasons, I ended up using some of the extra 1/8 id tubes as spacers between the links on the pin that goes through the "back link".
I took a 5/32" end mill against the ends of the 3/32" diameter rods so that they sat between the ends on the jig, without having to be held.
Set the jig on one side, with the pins horizontal and the parts not clear down against the aluminum
Make sure they are clean and not covered with oil etc

Cut the solder into little maybe 1/16 - 3/32" long chunks with side cutters, and maybe smash and curve them so they will sit on the place you will set them (read below).
I used a regular old propane torch. If you are like me when I learned this, and most people, you are using too much heat to silver solder (especially small parts) .
Get the parts evenly hot but not smoking hot (450 is NOT that hot! especially for these little parts!)
Then set the torch carefully aside.
Use a small screwdriver or nail or maybe even a tiny artist paint brush to put the flux ONLY where you want the solder. The flux will boil a little when you do this.
Use tweezers or something to carefully set a little chunk of silver solder it on the place where it you want it to melt.
Pick up the torch and slowly, carefully and evenly heat the part first then the solder. When it hits 450 the solder will flow into a nice shiny weld, immediately take the heat off.
Do both ends then flip the jig over and do the other side. Rinse and repeat.

If you put the flux on before you heat the parts, it will be long gone when you need it. Too hot will boil the flux away and boil the solder, make your parts ugly, etc , not good!
You can not possibly hold the the solder in your hand like when you solder for electronics! At best by holding it in your hand you will have way way too much and probably NOT where you want it!
Form the little chunks of solder with pliers or whatever so they will sit where you want it before you melt it.
This is million dollar advice.
Like golf, bowling and billiards; easy does it!
;-) Dave

 

[mjonkman]

That solder sounds a lot like the "silver bearing" solder that I was looking at, at the hardware store. To differentiate I'll just call what I was doing silver brazing using stay dilv 45 or something like that. I believe its melting point is more like in the 1100 degree range. I'll dig out my plumbing solder and see what it says on it, I'm not against splurging for another roll of solder. There was a big discussion that I read up on HMEM yesterday and silver solder and there was a lot of disagreement among people about exactly what was silver soldering. In the past it appeared that silver soldering is what is now called silver brazing (the stuff I was using) and now silver soldering more aptly refers to silver bearing solder (soft solder - probably what you were using) that melts at low temp. Makes it very difficult to figure out what folks are actually talking about :-(

Thank you for the advice - using a little snippet of solder will really help keep things under control and not waste solder - whether its the cheap stuff or the expensive stuff. I think I can use the steel version of the jig I created vs. making a new aluminum one. On my first attempt last Friday I just used straight pieces and didn't make the ends of the rod concave so I had to more or less hold things flat which of course soldered the stuff to the jig Your way sounds much better and keeps things from having to rest on the jig body itself. Thank you.

I may just get the x and y working on the DRO right off and get the z scale mounted properly then take a break finish the engine then get back to creating parts to connect the z-axis read head to the knee.