Valve Gear Dimension Errors?

[atgordon]

Although I haven't started the build of my Super Simplex, I have been using end-of-day time to put all the drawings into my CAD/CAM package (Fusion 360).

I have recently come across a problem with the valve gear.  Either I have messed up, or Martin Evans is 0.047" short!  I am trying to fit the combination lever from the valve gear crosshead to the main crosshead via the anchor link and it doesn't fit!  They are clearly out of alignment.

I checked all the Super Simplex errors pages, and no one else has mentioned this problem, so I'm guessing that I am missing something very simple and obvious ... The graphic below shows how things should work ...




The following shows the problem I'm having: 



If anyone is a Fusion user, they can find the file HERE

I have two drawings that can be downloaded that show the dims I'm using as well, as well as ME's original drawings.

DRAWING 1 CYLINDER ASSEMBLY
DRAWING 2: Martin Evan's crosshead
DRAWING 2 CROSSHEAD ASSEMBLY

Appreciate any advice!

Thanks,

Tony

[uuu]

Can you fit the "outside cover plate with drop arm" in either of two ways - with the drop arm inwards instead of outwards?



Wilf

[atgordon]

Jan 12, 2019 11:56:37 GMT uuu said:

Can you fit the "outside cover plate with drop arm" in either of two ways - with the drop arm inwards instead of outwards?



Wilf

Nope ... although I did check that!

Martin Evan's drawing shows it assembled facing out (plus, reversing it would set it back 0.218" - 0.109" x2 which is way more than the 0.047" I need).

[gt]

I had the same problem, after checking the dimensions many times i made new outer crosshead plates to fit the alignment

[atgordon]

Jan 17, 2019 9:01:12 GMT gt said:

I had the same problem, after checking the dimensions many times i made new outer crosshead plates to fit the alignment

Thanks, that's what I ended up doing (well, in CAD).  Instead of a 7/64 (0.109") offset as per ME, I have gone for 1/16 (0.0625") which evens everything up beautifully.  I'm sure a 3/64" off isn't much in our small scale locos (so the combo lever is off to one side by  47 thou ... big deal!)  but CAD is unforgiving ... thankfully!

Wish there was a better way of noting drawing errors. We're not the first to notice this and won't be the last I'm sure!

Tony

[JonL]

smalllivesteamengines.fandom.com/wiki/SmallLiveSteamEngines_Wiki

Thats a chunk of the idea behind this wiki, to record errors in the drawings. Sounds like a good one to add.

[builder01]

I'm looking at the error presented here. After going over my own Super Simplex drawings, the error is quite real. My Super is up and running and has been for well over a 2 years. I will have to go out to the shop to see what is going on here on my completed Super. Probably what has happened, the combination lever is not exactly straight up and down. It probably splays out from the locomotive to fit into the union link. There is nothing keeping the combination lever exactly vertical, so, it has probably been swung outward (by 3/64") to meet the clevis of the union link. Not really a big deal, but it actually can be built even with the error. (I did, oh well!).

What to do about it, looks like modifying the drop link plate to get the pin in the "right", or at least "better" position for the union link.