Stuart #1 Reverse Drawings

A question for anyone who has built the reversing gear for the #1. When I got the castings for my #1 second hand many years ago, also included were the reverse gear castings. I have started working on them and the drawing I have although showing most dimensions is more of a GA than parts drawing. Many of the parts don't have all the dimensions (like the eccentric sheaves and straps ). When I got them the box was open and I am wondering if there was another sheet of drawings that is missing, dimesioning the individual parts , there is one with the 5A reverse gear castings I have. The drawing I have is numbered 70090 dated 18.10.56 Alt # 32 20-1-67 and issued 18 Sep 1975.

John

What is missing is on the main engine drawing. Straps are the same as the single one that comes with the main kit, diameters and widths of the sheaves are as per the single.

Couple of the links could do with dimensions but they are the non critical bits so you can get away with scaling from the drawing. Vertical link needs to be free to move.

Some make the sheave as one which is more difficult to machine but a little easier to adjust. Others do two separate ones to make machining simple. Although angle is not stated the valve leads the crank by 120deg in either direction.

Edited By JasonB on 31/01/2022 07:49:55

Jason

Thanks for the reply. What I have been doing is as you suggest, using the main engine drawings for the sheaves and straps and scaling from the drawing elsewhere as necessary. I was just wondering if there was another drawing sheet I was missing? At the moment all I have left to do are the eccentric straps and rods.

John

I've finished all the parts for the reversing gear for the ST#1 except for the valve rod head and the die block. On doing a trial assembly there is a problem. The valve rod doesn't line up with the expansion link. As can be seen in the picture below the link is a good 5/32" further out. I have an idea how I can fix it by making 2 new parts but I was wondering if others that have made the #1 reverse gear have had the same problem and how they got around it. The valve chest and cover and all the parts of the reverse gear are dimensioned according to the plans.

John

Can you post a side view that goes a bit lower down so I can see the eccentrics

Looking at mine I would say that the eccentrics need to be closer to the crank throw to make everything line up, it might be just that simple ? Noel

Here are a couple of more pictures with different views. The first, Jason, is from the back and shows that with all the reverse linkages lined up the eccentrics are spaced out on the crank shaft and the valve rod and the expansion link don't line up.. The second shows the eccentrics moved in on the crank to line up the valve rod and the expansion link, but now the reverse lever is spaced out from the rest of the reverse linkage. The position of the reverse lever is fixed by its fastening to the slotted link which is bolted to the valve chest cover. The obvious fix is to make a longer 1/4" pivot pin and a spacer between the reverse lever and the rest of the linkage. But my question is have other people had this problem or am I missing something, or are the drawings of the reverse gear in error?

John

Edited By John Purdy on 17/02/2022 18:32:01

John, have you checked that your valve rod ctr is 2 1/8" from the cylinder ctr to match the 2 1/8" centre line of all the valve gear? First picture looks like you have the valve gear too far away from cyl ctr as it should come about 1/2 way over the side of the chest cover

Edited By JasonB on 17/02/2022 18:43:07

On mine the link down to the expansion link is off set in its bracket on the cylinder by about 1/8" to make things line up. Hope this helps. Noel.

Jason
I had previously measured the valve chest cover at .250" and the valve chest at .750" as per the drawings. The valve rod is in the centre of the valve chest, ie. .375" in from either edge. Cylinder bore is 2.000". I've just taken off the cyl. top cover and the measurement from the outside of the valve cover to the edge of the cylinder is 1.752". Therefore cyl. centre line to valve rod centre line is 2.127", close enough to the drawing dimension of 2.125"

Yes that's the problem, if I move the whole reverse gear assembly over to line up with the valve rod then the reverse lever doesn't line up with the rest of the reverse assembly as shown in the second picture above.
John

Edited By John Purdy on 17/02/2022 19:10:39

As noel says it looks like you have the vertical link central in the bracket as the bronze either side looks to be the same width but it should be offset.

Edited By JasonB on 17/02/2022 19:10:48

Noel and Jason

No that's not the problem. The outer boss on the support fastened to the valve chest which supports the vertical link is .375" wide as per the drawing ( the other side is actually about 5/16 not 1/4 as the drawing but it is in the wind so to speak).

John

Got it. Sizes on the drawings don't add up.

If you take the bracket first then from the ctr line you have half the 5/16" which is 0.156, bracket 0.375" and the 5/32" arm thickness off of the levers 1/4" boss leaves 0.094" to the inner edge of the lever. Total 0.625"

If you then work out the position of the slotted arm from ctr line you have half the 3/4" chest so 0.375", cover 0.25" and the arm is 0.156" thick. Total 0.781"

Difference between the two is your 5/32"

I think I would set it up as per your second photo and add a spacer between lever and bracket.

Edited By JasonB on 17/02/2022 19:43:19

At the end of the day it has to fit !!!! Something is wrong, so.The eccentrics can be moved towards the crank ! The slot in the mounting bracket needs to be widened to allow the verticle link to lineup and a spacer fitted to fill the gap and may be a new pin made. simple ! Noel.

Thank you Jason, I'm not crazy after all. I had also added up the dimensions as you have done and came to the same conclusion, but was wondering if I was missing something. I'm sure many examples of this reversing gear have been made to these drawings, how many others have had the same problem and how have they got around it? Are Stuart Turner aware of the errors, are the current drawings the same as ours or have they been amended?

John

Noel

That's my plan. Make a new longer 1/4" pin and a 5/32" spacer between the reverse lever boss and the bracket on the steam chest. Everything would then line up. I was just wondering if I had screwed up of was missing something. It now appears that it is the drawings that are in error.

John

Glad to have tried to help ! How old are your drawings ? If they are new ish and not corrected send me a correct dimentioned sketch and I will see to it they go to Bridport ! Your engine looks good. Noel

Noel

Before I read your post I had sent off an e-mail with some pictures to Stuart Models explaining the problem and listing the discrepancy in the drawing dimensions as laid out by Jason above and confirmed by me . We'll see what their reply is, and when I get it I will pass it on here. The info on my drawings is as follows: DRG #70090 dated 18.10.56, ALT. #32 20.01.67 and issued 18 SEP 1975, so fairly old, Stuart Turner pre Stuart Models (they appear to be the same ones Jason has). Thanks for the comment on the engine ( more pics in my album ).

John

Edited By John Purdy on 17/02/2022 23:04:58

Got a reply from Stuart Models this morning. Seems they are still using the same plans and are not aware of the problem. Here's a quote from their msg.

"We are still working from the same drawings as you seem to have,

I haven’t had anyone notify me of this issue before, but this maybe that they have worked around the issue.

Will moving the reverse shaft bracket solve the valve rod alignment, also on our engine, there is a spacer between the reverse shaft bracket and the reversing lever, so this may be the get around."

Looks like their fix is the same as I have come up with!

I've added a post to the "Drawing Errors " section about this error in the drawings.

John

Edited By John Purdy on 18/02/2022 17:12:51

Dear John, When down in the west country I often go down to to Stuart Models at Bridport, I will try to remember next time and take my No1 with me to show the problem and refer them to your communication. May be they will issue a correction. Noel.