Freelance mill engine from Stuart castings.

[steam guy willy]

Hi Chris, this is a picture of the Allen valve gear... it is basically Stephensons  valve gear but with a straight expansion link . I found this on Graces Guide from an edition of the Engineer magazine from the 1880's here is a pic of it .....It is quite a compact arrangement and i have not seen it before on a mill engine. Just watching the weather news and it seems like pretty awful weather in the USA ...hope you are ok  They have called it a Bomb Cyclone ! not heard of that before.

[crueby]

Wow, thats what the main hoist engine on the Marion 91 has! I didn't know what it was called. I figured they used it since that engine never ran for long periods like a loco or mill engine, but was set up for short full power pulls, so they didn't care about feathering the steam usage. The link on the shovel is very short and a straight line.

[steam guy willy]

Hi Chris, Good to hear about the Marion...I think this type of linkage was made so that you only had to pull the lever a short distance for a lot of motion travel.?  I have been scheming the linkage by dead reckoning as i only have the picture that is a steel engraving from the 1850's ,and i don't know how accurate the dimensions are....So a few pics of the build so far......!There is a vid about the Allen valve gear here..It is rather lengthy and there are no actual measurements <a href="https://www.youtube.com/watch?v=meCkaR7gGIM" target="_blank">http://www.youtube.com/watch?v=meCkaR7gGIM</a>

[steam guy willy]

I have made all the parts to see how it goes together and was surprised at how much the lever had to move to get from one end of the link to the other !!! I thought it would only have to move a small amount ?? I had to change the sheaves as there was not enough offset on them. so quite pleased that the 'dead reckoning ' seam to have worked out... So , sort of finished ?!! just need to make all the parts from steel etc and also a base and the pipe work......The actuating lever is at the back....

[crueby]

Coming together nicely - good thing you are making the mockups to check things before making the metal parts. I did the same thing on a sailboat cockpit once, used stacks of 2x4's, flat boards, and extension cords to mock it all up and see if I fit in it comfortably! The original 3D modelling!   

[steam guy willy]

Hi Chris, thanks for that ...have you made the Marion Allen gear yet ?? it would be interesting to see real dimensions ?  You could call the finished engine Robin ??!!!! wi tell you why later !!!...saw this Volts Wagon  !! well it is electrically powered !!

[crueby]

Hi Chris, thanks for that ...have you made the Marion Allen gear yet ?? it would be interesting to see real dimensions ?  You could call the finished engine Robin ??!!!! wi tell you why later !!!...saw this Volts Wagon  !! well it is electrically powered !!

Ive done the 3d model for it, going to be quite a while before I build it in metal. I'll get the drawing page out...

[crueby]

Here is the (model sized) drawing of the linkage from the Marion:

It is actuated from a large pivoting linkage under the floor, with long rods leading back up to the operator position at the front of the cab.

Funny you should mention Robin - for the fundraising effort on the Marion, they are going to name it the 'Maid Marion Project' to get some extra attention.

Love the VW bus/train!

Also, attached is a copy of the patent that Marion did on their version of the linkage - the straight link is not the focus of it, more their version of the sliding parts, but it does talk about the straight link and its advantages in that context.

[crueby]

Willy, I was looking up the Allen gear, and from this quote

 "The Allan straight link valve gear (invented by Alexander Allan in 1855) combined the features of the Stephenson and Gooch gears. The reversing and cut-off functions were achieved by simultaneously raising the radius rod and lowering the link or vice versa."

it sounds like the Marion just uses the straight link portion of the Allen setup. Does your engine do the moving of radius rod? I don't have a good mental image of this, can't find a real diagram of the Allen linkage.

[steam guy willy]

Hi Chris, Thanks for the info.....Maid Marion was Robin Hoods love interest ...the well known outlaw from sherwood forest in Yorkshire !! I was wondering what the offset angle of the two sheaves are as it does not seem to appear very much on your drawing. Here is a drawing of the Valve gear i found somewhere recently. Love the work on the Marion bucket so far looking spectacular !! I have noticed on my engine that in mid gear there is still movement back and forth on the valve rod,  not very much but definitely not zero movement ??

[crueby]

Aha - that first drawing you show explains the text I found, moving both like that is an interesting arrangement. On the Marion, that second link to the valve rod is not there, the valve rod stays at a fixed position and just the straight link moves. So, guess that makes it a Half-Allen! Wonder if that is Half-Nelson's brother?   
For the Marion, they were not concerned with efficiency of steam on long runs, since they would have been stop/starting very frequently, so they  most likely just set the link at full throw and left it there. The only time they engaged reverse would have been when moving the machine with the tracks. Lowering the bucket was done by releasing the throttle, which had a bypass to connect both steam lines to exhaust to let it freewheel, and they used the brake band (controlled with a foot pedal) to control lowering the bucket under gravity power.

I did not work out the offset angles for the eccentrics yet on the Marion yet. It was way too close quarters to try and measure them on the real engine, I'll probably just work that out when I build the engine, and adjust it in place with a set screw to get the correct motion. The smaller slew/crowd engines did not use an external reverse linkage at all, they had a really clever internal valving to reverse the steam/exhaust passages from the single throttle valve.

Thanks for that diagram, I had not been able to find that.

[Steam Haulage]

Hi SGWilly,

I think you will find Sherwood Forest is in Nottinghamshire. The main road nearest to where I live goes there in a few miles. My grandchildren can easily cycle there.

I was born in neither Yorkshire nor Nottinghamshire so I can't say what those born there were might think. Probably the Tykes would be the most upset; they would expect you to know exactly where the Notts/Yorks border is what ever your heritage.

Jerry

[crueby]

Hi SGWilly,

I think you will find Sherwood Forest is in Nottinghamshire. The main road nearest to where I live goes there in a few miles. My grandchildren can easily cycle there.

I was born in neither Yorkshire nor Nottinghamshire so I can't say what those born there were might think. Probably the Tykes would be the most upset; they would expect you to know exactly where the Notts/Yorks border is what ever your heritage.

Jerry

Uh Oh - hope we don't start the NottingYorks history war!   

[steam guy willy]

Hi SGWilly,

I think you will find Sherwood Forest is in Nottinghamshire. The main road nearest to where I live goes there in a few miles. My grandchildren can easily cycle there.

I was born in neither Yorkshire nor Nottinghamshire so I can't say what those born there were might think. Probably the Tykes would be the most upset; they would expect you to know exactly where the Notts/Yorks border is what ever your heritage.

Jerry

Oh no, boundary changes again or is it gerrymandering ....remind me not to wear that pink rose again !!! sorry geography has never been my strong point ,and where is Rutland again ??!!!!......
willy....

[steam guy willy]

Hi All, went to the Norridge engineers show and tell last night and there are still a few places on the bus to go to the Ally Pally ME exhibition on Saturday 20TH Jan The bus leaves from Eaton Park at 7.30 am Hope to see people there !! also i have found out how to scribble on the photos with my Mac pooter....