Tug's Corliss Tandem Compound Project

[Ramon Wilson]

Hi Roger - thanks

Yes it is a bit mesmerising. Haven't run it since posting but it's getting there now. Just finished all the handrail stanchions which was a nice exercise on lathe and mill and have them all fitted. Barring rack is just made too and I'm pretty sure that's the last of the ferrous items so now it's the last knockings with a few brassy things and it should soon be done.

Thanks for looking in - Tug

[Admiral_dk]

Hi Ramon

Glad to hear that you almost got the next stage finished 

I should say hello from John too - he hopes that you're doing better than his sister (she hasn't really had any income since the first lock down started and have hardly seen anybody for most of all that time + his parents aren't doing much better).

I had my Offroader / Winter Bike started for the first time in years and out for a short spin today
Unfortunately it had to go back in the workshop as the clutch will not de-clutch    but I hope that the workshop will be available for at least one running model engine soon, before it has to do the next bigger project ....

I hope you both are doing fine - best wishes

Per

[Ramon Wilson]

Hi Per, yes quite close now 

Covid cases creep ever nearer but it has to said we live in a fairly safe area. Our hearts really go out to those less fortunate living in more dense areas and little to do with their time. Give John our regards - we are both fine, the garden and hobbies helping to take our minds off the dreadful news we are all faced with each day.

Good news however on the potential model engine project  I was going to revert back to the plastic but I have found a really nice subject so it's more cast swarf for a week or three once this one is finished 

Stay safe - Tug

[Ramon Wilson]

Hi Guys, Ferrous parts all done so spent much of today cleaning down ready for the brass. No pics as yet but they will come

It's just that during said clean and tidy I came across the 'lost' correspondence that I had with Peter Southworth after our initial conversation that kicked this project all off. A nice lengthy letter (remember them) dated 28Oct 1998  it is more to do with his experiments with PTFE bearings in a turbine powered 5" guage 0-6-0 loco that he was working on at the time (4.5" disc at 35,900rpm according to the letter) So whats this got to do with the Corliss I hear you ask?

Well, the last three line paragraph rather got my attention  - quote (verbatim)

 'How are you getting on with the Corliss engine? One addition that is needed is an oil filled dash pot on the governor to stop it hunting, mine was rather bad. I will design one in due course'. Unquote. (my underline of course)

Interesting to read that after the results with this one eh?

I don't recall ever hearing if he did - due to pressure of work, redundancy etc etc it would not be until well after he had passed away that I would actually begin this engine in earnest. The last I 'heard' from Peter was not long before he went. He had visited the Forncett museum and sent his regards via one of the museum helpers. Pity really as though we spoke many times on the phone and exchange letters I never did meet him - something I would have like to have done.

Despite this, no, I won't be adding a dashpot - well not at this stage that is

From tha 'ole shid' - Ol Tug

[pgp001]

Hi Tug

The Whitehead governor on Agnes has a dashpot, it was the only component on the whole engine where I managed to get hold of Peters original sketches, nobody knows what happened to all his other drawings but the governor one survived.

I have had to do all the drawings for Agnes (including this governor) myself on Solidworks 3D CAD, using a mixture of original P & W drawings and measurements taken from the full size engine.

I have also attached Peter's freehand governor sketch below as a PDF in case you are interested in seeing it.

Phil

Peters diagram



My version of the Whitehead governor without the oil needle adjusting screw, the main adjuster thread at the top is 10BA, I didn't fancy boring that out for a needle   

[crueby]

Very interesting setup on that governor - the oil piston damper is something I never would have thought of. Acts like a shock absorber on a car or bike? Do you know if that was a common feature on governors on full size engines?

[Ramon Wilson]

Thanks for that Phil - interesting to see how it's done.

The governor on the Corliss as designed is a Hartnell.(I think I previously eroneously referred to it as a Hargreaves  )

Arnold Throp, in his article on the single cylinder condensing version in ME refers to it as a 'Wilson Hartnell' Having done a search it would appear on first look that a Wilson Hartnell has two springs, one inner as usual but another connected across the weights. It seems these may have been fitted to diesel engines but the type with a single spring - referred to as a plain 'Hartnell' governor - were used on steam engines. The one thing I note (full size) is the the spring tension should be able to be tensioned by the nut on the top - a feature not possible on mine at the moment (I have a feeling that's as drawn but I may be wrong - will check tomorrow). I'm pretty certain a stronger spring will cure the hunting tendency however but that's as yet to be tried.

Fitting a dashpot in as your post would need a redesign, something I'll also consider at some stage if the stronger spring is not successful. Now I have 'scaled' the engine by the handrail dimensions the governor as fitted is too low really - certainly low enough to present a danger to whoever would open the stop valve  An increase in height is definitely on the cards

Thanks for the input, much appreciated

Regards - Tug

[kvom]

Greene engine governor has a dashpot.  How functional any of it would be for the model is dubious.

[deltatango]

Hi Tug,first sheet
I'm a bit late to the party here, we're away from home. In my set of drawings Peter S has titled the first one "Modifications to horizontal Corliss valve engines". On this are drawings for an "Oil filled dashpot" and I've attached what I hope is a usable picture. Fitting it looks to need a small mod to the governor column. Hope this helps.

David

[Ramon Wilson]

Hello David, thanks indeed for the drawing 

I had been giving it some thought as to how best to do this and was thinking on similar lines as opposed to modifying it to Phils version. I'm not convinced though that the flow of oil will be able to be effective scaled down to such small areas/volumes - it will need some close tolerance and need to move freely to work for sure. Still it's worth trying - another few days on it won't matter 

I haven't seen the drawing you have - as you are aware mine are dyelines copied from Arnolds originals that Peter had - there is no sheet of 'Modifications' included. I wasn't aware that Peter had done anything further to them - anything else of interest on the sheet to be aware of?

Enjoy your break, look forwards to seeing your next progress

Regards - Tug

[gbritnell]

My question would have to be " what viscosity oil would be used in something this small?"
gbritnell

[cnr6400]

My gut feel on the oil would be to start with 90 weight gear oil as used in rear wheel drive car differential housings. Anything thicker will cause a slow reaction to governer motion, and anything thinner would not resist / arrest the "hunting" motion. But as I said this is just gut feel. It may need a thicker oil yet, and a lot depends on how tight the 3/16" dia piston fits in the reamed 3/16 bore. In this case, .0005" clearance will likely work much differently than .001" clearance. Pity we can't ask Peter Southworth or one of the other guys who have passed on that had first hand knowledge of mill engines and models of them.

[Ramon Wilson]

My question would have to be " what viscosity oil would be used in something this small?"
gbritnell

Hello George, good to see you still looking in  - you too 'cnr'

I have no experience with dashpots but my thinking is contrary to cnr's thought and is that this will need to be very thin. As I see it it will depend on the size of bypass either in or around the piston - the smaller that is the thinner it will need to be - I would have thought.  If the oil can't bypass due to being too viscous or bypass area too small it seems to me that would defeat the object.

I notice the notation that 'piston diameter will need adjusting depending on oil thickness and or fit'

I have now decided to go ahead and modify the governor as such (and take the opportunity to make it slightly taller) - we'll have to see how it works out 

Thanks for the input guys

Regards - Tug

[Craig DeShong]

Been following along silently Tug and love your work; it will be interesting to see what happens with this new governor that is oil dampened.

[john mills]

interesting to se the govoner it would be a project units own in a larger scale may be .
my thoughts are thiol would need to be thin those thick sticky geariols would just glue everything .light  thin plain oil   but in this size even just air could be sufficient .
     John