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Author Topic: Getting ready for new steamer  (Read 486 times)

Bentwings

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Re: Getting ready for new steamer
« on: July 22, 2022, 03:45:23 pm »
Well it’s been a while as I’ve had so many interruptions . 
I finally got the engines assembled however an issue came up with those dog gone grub asrewc is set screws here the engine ran a few minutes very nicely then bam it stopped dead in its tracks . Well a nut that attaches the piston to the rod came off and caused the piston to jamb against the cyl head . This caused an immediate stop of all rotating things. The fly wheels grub screws cut small groves in the crankshafts and even the eccentrics slipped groovin their places on the crank shaft . Part of this was unclear instructions on setting the eccentrics and piston oft valves . Only one picture is shown and basically ally  says make it like this. There was no description of how itchy the piston port valve works. I spent hours searching the subject then considering they have made lots of these engines I thought I had really screwed up. After getting every thing apart and repairing damage best I could I set about analyzing  what was going on. I had to make a miniature puller to remove the brass flywheels then adapt it to removing the  eccentrics . I had a very bad experience in the shop with same thing in industry. I sad never again would I use set screws for anything but hold keys in kewsys. So I set about coming up with something to lock things to the crankshafts.  I respect chilertern highly but this detail escapes  me . Investigating I find the piston port operates as much improved slide valve
 By design it has “ lag “ which is similar to overlap in ic valve timing except steam has considerable energy built in this requires a preload cushion forvthe piston
In other words the piston gets a small hit of steam just before top dead center and bottom dead center. By adjusting the position of the piston valve you can even this out to smooth the engine operation . Also not noted is the fact that if you run on compressed air rather than steam this adjustment is quite different compressed ai has no expansion energy builtbin this is a complicated thing so I’ll move on to my fixes first there GSD to be dim means of accurately positioning the piston valve  this was solved as the steam chests have an open port that you can feed a skinny indicator into or just used the back side depth measure of your trusty “ very near “ calipers so you establish TDC of the piston then adjust the  piston port valve to some number that you determine as you tune the engines . You are adjusting over the diameter of a pretty small hoe so a little movement can make a lot of difference .  I got rid of the grub screws but using counter bores shaft collars these make up forvthe thickness of the  hubs  but I’m in the middle of redesigning this for easier assembly and set up. I may make new eccentric hubs or simply have some printed out of nylon plastic there  is not a lot of clamping force needed .  Needless to say I now have a large supply of shaft collars and couplings as I tried to purchase what I needed but often got the wrong stuff or ordered incorrect parts . But I did learn somethings.

In the mean  time our small lathe smoked out the spindle bearings and is under repair. , as a result I’ve placed my boiler on hold as I have enough to do now .  The eccentrics have two 3mm flat head screws holding them together . These are not sunk quite deep enough to be flush so I’m working on fixing this as I need a spacer representing the existing hub. The final solution is to build the hub into the plate and be done with it. In the process the hub will now have ability to be assembled either inside or outside .  Some steamers simple bend the eccentric connecting rod but I’d rather not do that as it puts a side load on either the eccentric or the piston port piston. As a result I need  spacers for the steam chests but these are just flat brass of given thickness. Plus’s a little longer screws . So it’s all going back together.  I added my larger tv screen to my lap top so I now can see screen detail better and I’m starting to re learn S loud works  it’s been years and several revisions so a little slower progress than I had hoped. These details would be very easy for chilertern to add. They will have to do cost analysis but I’ll give them my drawings and pictures. In hopes they will incorporate them.   
I have a pair of steam turbines that I plan on driving the PMResearch generators with. This not working I have a bunch of stepper motors just waiting to be put to work .   So I’ve been busy. I haven’t un my engines as I planned but I will shortly . As with all my previous “toys” Ill run them a lot the mill engines really need a better oil  system so that’s on the back of my mind too . I have a standard steam oiler but the bearing need better than drip I YHINK I also have all the small ME taps and dies now  so I’ll come up with something I did try both 10 weigh motor oil and air tool oil Air tool oil gives freer operation and even though it’s like water it works well oil is sticky after time and takes a while to loosen up.

Byron