Member postings for John Purdy

Rod
    Thanks for the pertinent section of the current plans. It looks like the basic dimensions of the slot are the same as my plans but a lot of other dimensions are given which makes it much clearer. Currently the slot in my rod is 5/16" wide for the whole length so I will have to mill/file out the bottom 3/16" to 7/16" wide. This will allow the 5/32" deep bottom half of the bearing to be inserted and slid up to mate with the top half.
    I also see there is a note at the bottom left of the your image that says to remove the inner flange on the top half of the bearings. I would think that it could be put in at 90 degrees and then rotated and slid into position, so is there a reason given for why the flange is to be removed?
    Did a trial assembly of the beam, pump rod and pump body and found that with the rod made to 6" between bearing centre and pin at the bottom as per the drawing, it is just too long, with the end of the rod hitting the top of the pump body. So back to the torch to un-solder the end, cut 3/16" off the rod and re-solder it back on. Fits much better now as can be seen it the picture.
John

Edited By John Purdy on 12/04/2022 02:17:59

Edited By John Purdy on 12/04/2022 02:31:21

Steve

Yes, that is the only drawing of the con rod little end and its bearings that is on the plans. Sounds like these dimensions have been changed. It would be interesting to see how these are shown on the current plans.

As for the pump rod bearings the plans show the beam pin journals as 5/32" dia. but the bore of the split bearing as 3/16" dia. which obviously doesn't work. I opted to make the bore 5/32" to match the beam pin journals for the reason given above.

John

Steve
Thanks for your reply.

I have finished the pump rod but made the bearing bores 5/32" to be the same as the pin as drawn. Seemed like a better idea than a 3/16" bore as shown, as that would leave only a 1/32" wall in the bearing. (Note he cotters are still over length and will be shortened on final assembly when the bearings are run in. )

Below is a snippet of the drawing of the little end of the con rod (not too clear as I said the drawing is well faded ). The drawing appears to show the slot as being stepped, 5/16" wide where the bearing is and 7/16" wide down to the bottom of the slot. As shown the bearing is 7/16" across the flanges but the depth of the square bottom half of the bearing is greater than the length of the 7/16" width of the slot, so how is it to fit in? How does this drawing compare with your newer one?

John

Don and Neil

I am also missing MEW 313 here in Comox BC. Got 314 two weeks ago and 312 about 2 months ago. Naturally the missing one is the one with my article in it!

John

Gary

I have used thick bucher's cord (cotton string about .070" in dia. ) wrapped around the pipe, ends held in place with a drop of CA glue, and painted with flat white acrylic paint. Looks quite prototypical. You can see it on my Clarkson's compound mill engine picture.

John

Dave

I've just re-sent my PM.

John

Dave

I just checked my sent box and it shows my message as being unread. Have you checked your message inbox? Its the envelope shaped icon in the login line at the top of this page, between "Settings" and "Friends". It should be flashing.

John

Dave

I've sent you a PM.

John

Having finished the Stuart beam engine I've decided its time to finish the Sanderson beam engine. Its only been 42 years since I started it! Starting with the con rod I find that the casting is slightly over 1/8" too short to make to the drawing dimensions. After some head scratching and many calculations I have come come up with a length between bearings that I think will work and just fit within the as cast length. Now the next problem is, there appears to be a number of errors/discrepancies on the plans for the little end of the con rod. The plans show the bearings as being 5/16" wide but the journal in the beam pin for the bearings only 1/4" wide. If the bearings were 1/4" wide with the arms on the fork 3/16" wide (vice 1/4" wide as shown ) which is how the drawing scales (not always a safe idea! ) then it would fit. Also, as drawn, the bearings appear to be impossible to fit into to slots in the fork end. The slot is 5/16" wide but the bearing halves have a 7/16" wide flange on each side. The top semi-circular half can be put in sideways and rotated into position, but the square bottom half can't be fitted. I have a couple of ideas for a solution, but what have others done?
Another discrepancy is the bore on the pump rod bearings is shown as 3/16", but the pin journals are 5/32" dia.
The plans I have are original Clarkson's dye-line, dated 18/10/69 and are well faded, having been exposed to sunlight for too long.
I'd be curious to know if these errors show up on the current plans.

John

I should have said my lathe is a S7B with power cross feed. As Speelwerk says the saddle and the apron are different from the earlier non power cross feed model, thus the screws will be different.

John

Ivy

On my S7, serial # SK127323 mfg 1976, the screws are all 1/4 BSF threaded full length, screwdriver slotted end. Lengths as follows left to right: 2.750 round point, 2 910 dog point, and 2.750 round point. The holes in the saddle are counter bored .275 dia. by 1.950 deep.  Hope this helps.

John

Edited By John Purdy on 16/03/2022 17:09:42

Chris

This is what I use on the oil nipples on my Myford. Its on the spout of a standard pump oil can. The end is turned down to just fit in the hole in the nipple and a small slot is filed across the end. In use it is pushed down into the hole in the nipple sealing on the curved surface, the end depresses the ball and the slot allows the oil to flow into the nipple. Works very well and costs nothing ( save the oil can ).

John

I just received the locking ring from Paul. For anyone needing to make one I have measured it under high magnification (20X )and the thread is 55 deg., 50TPI, .388" OD. The bore tapers from .273 on the outside to .325 on the inside and the rest of the dimensions are as Paul has shown in his post I measured the angle by comparing it with my small 60 and 55 deg. threading tools which were ground on the Quorn so should be reasonably accurate.

John

Edited By John Purdy on 28/02/2022 20:26:42

I have a Starrett as in the picture, and it works very well. The blade is tensioned by turning the lever at the top right. As far as I know it is still available as it is still listed by the tool suppliers I use.

John

Is there a convention on engines with reverse controlled by a lever, such as the ST5A etc., for which is forward, up or down? When I try to think about it logically I can make a case for either.

John

Dave

I've sent you a PM.

John

Dave

If you have access to it, I just remembered that there was a series in Engineering in Miniature by Andrew Smith on building the ST Cygnet (basically a #5A ). I have dug it out and it ran from May '81 to Dec '83. In one of the installments he details a method of machining of the double eccentric, also an alternative.

On a totally different note, I don't know if you are aware, but you can prevent the "smlies" showing up at the end of a bracketed statement by putting a space before the final bracket.

John

Edited By John Purdy on 20/02/2022 20:10:48

Edited By John Purdy on 20/02/2022 20:16:30

Dave

Your right again! I missed the groove in the eccentric strap being offset so the face is flush with the sheave. So ignore the extra 1/64" in my previous.

Is there any reason why the larger dia. on the crank has to extend out beyond the bearing?

I'd be curious to know how you machined the eccentric pair. I've looked at it a couple of times and tried to visualize how to machine it but haven't had much success.

John

Dave

You are right, the bearings have to be mounted with the 3/16 flange inboard. I was using the bearings with the 3/16 flange out as that what it looked like on the reverse drawings. Should have checked the crank/ bearing/bed opening, duh!

With the bearings the right way I get the clearances as:

Bed plate centre line to bearing outer face now 2 3/16"

Therefore valve rod centre line to bearing face now 3/8"

The way I calculated the valve rod centre line on the eccentric rod to the sheave face was: the ears on eccentric rod fork are (1/2"-9/32" )/2 = 7/64" wide, therefore centre line of fork is 7/64+9/64 from face of rod in slot in the strap, the edge of the slot is 1/8" from the face of the strap, the sheave is 3/8" wide, but the strap is 11/32" wide therefore the sheave extends out beyond the strap by 1/64", for a total distance fork centre line to sheave face of 7/64 +9/64+1/8+1/64 = 25/64 (.390 ) resulting in the sheave face being .015" into the bearing for things to line up. This doesn't take into consideration the 1/16" extension of the crank dia beyond the bearing face.

So it sounds like to make things line up the bearing face will have to be skimmed and the sheave counterbored for the crank unless we're both missing something!

So as you had initially found there seems to be a problem. Sorry for me confusing things.

Interesting that both the #1 and the #5 reverse gear have problems

Thanks for the kind comments on my engine.

John

Jason

When I said in my previous post "just add 1/4" to the 1/2" dia. - - - - " I was thinking you were talking about the spacer not the whole lever but making the whole reverse lever out of the solid would certainly be a possible solution. Wouldn't actually be much harder as the casting (which is malleable iron and machines pretty much like steel anyway ) needs to be machined all over.

As far as fabricating the bed plate for the 5A, that's definitely possible but where I live it is next to impossible to get raw materials.

John