Member postings for John Purdy

Is there a plan to replace the current non-functional spell checker in the post editor? Tonight, although I know it doesn't work, without thinking, I tried to invoke it and all that comes up is a blank page with "Spell Checker" and "Cancel on it and it freezes the page. The only way out seems to be to go back one page or re-click on "Forums", with the result that everything previously typed is lost. Most frustrating.

John

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

I have used Loctite PST high temperature  thread sealant #567 on my boiler fittings (internal and external), for many years and have never had a problem. Its a white paste in a tube, Loctite part #56747. It doesn't set hard so fittings can be easily removed in the future. According to the spec sheet its strength reduces to 55% of initial strength after 1000 hours exposure at 250C (482F). That's equivalent to a boiler pressure of about 550 PSI.

John

Edited By John Purdy on 25/01/2022 18:20:19

Edited By John Purdy on 25/01/2022 18:51:58

Jason, yes I believe that is the eccentric, the chucking piece is offset.

Martin, the larger of the two round cast bronze sticks is material for the main and beam bearing bronzes. That is what was supplied for them with my castings which came from Clarksons in '82.

The two castings to the right of the beam you mention are the support for the parallel motion anchor links, and no, only one is required. It is fastened to the top of the support bracket between the cylinder and the column.

John

Jason, I'm not quite sure what you mean is the piston castings?

Of your extra bronze castings I think the smaller of the circular ones with the chucking piece may be the piston casting. I seem to recall when I made mine that the piston was a similar casting. The finished piston is 1" dia. by 7/16" thick if that fits with its dimensions ( allowing for a machining allowance ).

John

Bill

I've sent you a PM.

John

Jim

I have a small home built kiln/oven that I use for heat treatment and silver soldering items too large for my torch. Works very well. It is controlled by a home built controller which keeps the temp within about 10 deg which is OK more most uses (I have a PID controller which will keep it to much closer tolerances if I ever get around to installing it). Its rated at 660 watts @ 240 volts. Further pics in my album, including cutting diagrams for the insulating fire brick linings.

John

Edited By John Purdy on 12/12/2021 18:46:18

The parts list I have is dated 1972 so I would think the plans, although not dated, are of the same vintage. The plans show the dimension to the bottom of the slot as 19/32", the same as in Andrew Smith's book (1987 edition ). This is definitely too short and would foul the beam before it reached the top of the stroke. If the 19/32" was to the centre of the U it would probably just clear the beam. I would be curious to know what the current issue of the plans show for this dimension?

John

Jason
Thanks for your reply. Since my post I tried a different method of determining the depth of the slot. With the beam at the top I scribed a line on the dummy rod along the bottom of the beam. I then drew a line horizontally where it intersects the left hand vertical line that represents the edge of the 1/4" wide fork and another line 3/16" lower to represent the bottom of the curved slot. The distance from the centre of the upper pivot hole to this lower line is just over 11/16", which agrees with your estimate of the minimum dimension. Barring any other suggestions I think I will go with a dimension of 23/32 or 3/4" to give some clearance. I wonder how many connecting rods have been scraped by being made to the plan dimensions?
John

A question for anyone who has built the Stuart beam engine.

I've started to work again on the one I acquired part built many years ago. I have just finished the links for the parallel motion and have stated to layout the holes in the 1/2" x 5/8" bar for the con rod. At first glance it appears that the 3/8" wide slot in the top of the rod as drawn is not deep enough to clear the beam when at the top of the stroke. The drawing shows the bottom of the slot as 19/32" below the centre of the 3/16" pivot pin hole, which means that the parallel portion of the slot only extends 13/32" below the pin centre (the bottom of the beam is 3/8" wide ) and looking at the beam when at the top of the stroke the bottom looks to be considerably more than that.

So I made up a dummy con rod to check the clearance and the angled piece on the dummy rod just clears the beam at this distance, perhaps slightly less. It looks like the 19/32" dimension should be to the centre of the radius of the semi circle at the bottom of the slot, not the bottom. I have searched the site for any mention of this but found nothing. Am I missing something?

Just as an aside, ( and not implying anything ) the Unimat SL lathe spindle uses two A13 magneto bearings ( the same as the Quorn ), and the preload is provided by a pair of disk springs ( >< )bearing directly on the outer race of the bearing at the pulley end. Out of curiosity I was going to measure the preload that is used on the Unimat but my spring scale that I used when I did my Quorn spindle seems to have grown legs and disappeared!

John

John

Thanks for your explanation. Your reasoning makes good sense and I can see why it might be superior in that aspect. Perhaps a better way to utilize the disk springs would be to have a sliding sleeve 2 x as long as the bearing diameter bearing on the bearing outer race with the other end bearing against the disk springs to provide the preload. This would alleviate your concern of little support for the outer race and provide for heat transfer, at the same time providing a uniform preload around the circumference of the outer bearing ring. Just a thought.

John

Duncan

That was my concern. When I got my castings from MES, included were 6 springs for the spring box. A cursory inspection of them showed that there was a difference in the spring rate between them. This would mean that if made as drawn, the preload would not be uniform around the bearing. . Whether this uneven preload would make any difference in the operation of the spindle in the type of service that the Quorn spindle is used for I don't know, but that is why I went with the disk spring design. In the case of the turbine gearbox you mention I suspect that uneven loading on the bearings at those speeds and prolonged running would very likely cause premature bearing failure.

John

John

I'm curious as to why you think the spring box arrangement for preloading the bearings is superior to the disk springs washers. Could you elaborate?

When I built mine I used the disk springs as I felt it would be easier and produce a more uniform preload. In use it has been perfectly satisfactory, and I feel was easier to make.

Derek

I have a PDF of the drawing of my modified spindle using the disk springs also a short write up of its construction. If you are interested I can send them to you.

John

I did mine many years ago and I agree, for the time taken is definitely worthwhile. Also did his modifications to the cross slide collar and added the quick retracting topslide. The later makes screw cutting so much faster. The larger graduated collars and the locking arrangement are much superior to the original Myford system. The larger collars are much easier to read (particularly the topslide ) and can be reset with no risk of moving the slides. Although considerably more work I highly recommend them.

John

Here's some pictures of my latest project, a Red Wing hit and miss stationary engine. I'm not happy with the paint job or the colour, but that will have to wait till next spring or summer as we are into the windy/rainy season out here (I paint outside). Haven't had a chance to run it yet, it's been raining for the last week. It's got to be my fastest build, started on 12 Jun 21, not much else to do with this pandemic! Now back to the Stuart beam acquired, part built, in the mid "90s.

Ignition is via a Nissan coil (courtesy of my auto mechanic son) hidden in the base. These hi energy coils are used for each individual cylinder, are small (2.5"x1.75"x.75" ), work well on 6 volts and have a built in transistor trigger circuit so when used with points minimal current goes through the points ( new ones aren't cheap though!).
John

Edited By John Purdy on 18/10/2021 18:59:41

Edited to get rid of the closing bracket induced smiley

Edited By John Purdy on 18/10/2021 19:02:16

Kwil

That info on the changeover to metric screws agrees with what I have with my lathe. It was bought 22 Sep 77 in central Canada and has Serial #SK127323. The manual that came with it, S.723Q (no date) shows the metric screws in the parts list. The old Myford site showed serial#s SK115830 - SK 129944 were manufactured between 1974 - 1976. ( not sure were it came from but I also have a note that #SK122657 was made Jun 75 and #SK136311 was made Nov 77). So based on that I suspect mine was made mid to late "76.

John

Ignatz

Just thought, the studs holding the change wheels to the quadrant are 1/4 BSF. You could use one of them to check the hole sizes, as I said, if it won't go in will be M6.

John

I wonder how many drivers in real life got a shock by accidentally leaning on the spark plug !!