Benson engine

[Jasonb]

You will probably get a smoother running engine if you time it to have about 7degrees lead rather than zero that your setting method is giving at the moment. It lets a tiny bit of air/steam into the cylinder just before the piston reaches the end which has a cushioning effect but that is something that can be played with on final assembly.

That was what I found with the bracket it was just moving slightly and tightening the screws and making sure it was seated solidly cured the squeak.

[kvom]

Thanks for the tip on the wrenches.  I will be ordering a set once Amazon gets the Prime issue fixed (trying to charge shipping currently).

When I retimed the engine for a second run in the opposite direction, it ran much better than the first run.  Whether the lead changed or not is hard to tell given that I'm eyeballing the valve nut.  Since I'm going to take it apart now I'll see how it goes after the reassembly.

[Jasonb]

Once you know the valve nut is exposing equal amounts of port either side the actual "timing" can be done just by looking at the high point of the eccentric. As you have it now it is 90degrees ahead of teh crank so you just need to slacken teh grub screw and move it a little more in teh direction of rotation. If your grub screw is placed inline with the max throw of the excentric at the time it is made it is quite easy to see where things are just by looking at the angle of the hex key.

[kvom]

That's what I figured.  I'll give it a try.  That said, my view of the valve nut and centering it is hardly exact; whether it's dead on or 7 degrees +/- might be hard to tell.

I probably should replace the screws holding the steam chest together with studs (2-56 all thread) once it's apart.  Then I could remove the cover when timing and have a better view of the ports.

[kvom]

I received the set of Moody small open end wrenches today.  Excellent quality as it appears.

[b.lindsey]

I think you will find them most useful Kirk!!

Bill

[kvom]

After 6 days out of the country followed by 4 days fighting a cold I imported, I decided it was time to do something in the shop.

Normally I've been buying oil cups from various model supply vendors as they're cheap and look good, but this time I decided to make 4 for the Benson.  After all, I've had my little CNCed LMS lathe for over a year and thus far have only made the frame spreaders for the Coventry.  These are made of 5/16" brass rod.

After firing up Mach4 and determining the X0 and Z0 for the turning tool, the tool is set at Z0 and the stock is tightened in the chuck while in contact with the tool.



Then it's a matter of running the program to turn the profile.

<a href="https://www.youtube.com/watch?v=qoJ56B6OmbA" target="_blank">http://www.youtube.com/watch?v=qoJ56B6OmbA</a>

I then reverse the stock and cut a second profile on the other end.  With two pieces of stock I get 4 cups ready for finishing on the manual lathe.



After some drilling and parting, I ended up with these.



I had intended to thread the ends, but since the eccentric straps are so thin I think loctite is a better solution.

For anyone interested, I am using eCAM to generate the G-Code.

[crueby]

Interesting to see the cnc lathe in action, thanks for the video of that!

[kvom]

Unlike the busy beavers on the forum, I've been lax on making progress towards finishing the engine.  With Cabin Fever 6 months away and no new project begging to be started, it seems like there's no rush to completion.

In any case, today I spent a bit of time in the shop.  First off, I milled a flat .01" deep on the end of the crankshaft.  Te idea is to be able to remove the crank and replace it without changing the configuration of the eccentrics.  I'd previousy turned a groove to prevent a burr from the set screw making it difficult to remove the crank.



Since I've decided to leave the engine unpainted except for the flywheel,  I'd like to keep the brass parts from tarnishing.  Terry Mayhew on the other forum  pointed me to Eastman Diamond Clear coatings.  I ordered a can each of the glass and satin versions, but tests on the some brass didn't show a great deal of difference.  So with the engine completely disassembled, I'll start to polish with Brasso to remove the existing tarnish and spray a couple of thin coats on the brass parts.



Started on that effort and got a few parts done before my energy gave out.  I still need to drill the eccentric straps and bearing covers to attach the oil cups.  Plus remake one of the governor arms that came unglued.

[b.lindsey]

Hope you are feeling better Kirk. Summer colds are the pits!!!  The oil cups look as good or better than store-bought ones

Bill

[kvom]

I did get the brass parts cleaned and sprayed, then did a partial assembly before other tasks got in the way.

I decided I needed to remake the arms on the governor after one came apart.  Originally I drilled a 1/16" hole in the lower end and glued the rod into both the arm and the ball.  Aside from one glue joint failing, I made the rod too long so that the balls were too low with the engine stopped.  The new design of the arm is to have an extension drilled and tapped 0-80.  Likewise, the brass balls are also drilled and tapped, and the rods are threaded on each end.

Here's the arm with a screw attached.



For scale, the separation of the two holes is .5".  With the governor assembled:

[kvom]

I now have the engine re-assembled, and next job is to time it and get it to run.  I have also designed an aluminum base for display that will be a future shop task.

For the governor to connect to the input, a "rocker" is needed.  This is a finicky part to make, so I drew it up in Solidworks, exported as STL, and sent it to Shapeways to be made in brass.  Hopefully this will work better for me than George's auto parts in stainless.

[kvom]

Started on the sub-base and initial did timing.  Timing is probably off a bit, but I'm doing some run-in before any tweaking.

<a href="https://www.youtube.com/watch?v=cGuvS2COk5c" target="_blank">http://www.youtube.com/watch?v=cGuvS2COk5c</a>

[Ye-Ole Steam Dude]

Just viewed it on Youtube and gave you a thumbs up.
Thomas

[kvom]

For the base of the engine, I decided to make an elliptical sub base that will in turn rest on a wooden plaque.  The sub base was machined from some 1/2" aluminum tooling plate I got on eBay.  It seems to have been Blanchard ground based on the finish.

The plaque in the pic is a bit large, so I intend to order a smaller one that hasn't been used for mounting anything.  Initially I'll attach the engine to the plaque with 2-sided tape until I decide if I want inlet piping to connect through the floor.

For anyone interested, I machined the ellipse from a piece of rectangular stock .3" deep.  Then machined soft jaws to hold the ellipse and milled the rest of the stock from the "bottom".