Member postings for John Purdy

Steve

Thanks for the link. I'll have a look at that and probably get more confused!

John

Ron

I have the the whole Eastern Belle series and can send you what you need. I've sent you a PM.

John

I’m looking at making a set of mitre gears, 20 tooth 48 DP using the two button method of making the cutter. I have done this for small spur gears before and they have come out satisfactory.

I have Ivan Law’s book and the ME articles by Dave Lammas ( Jul. 91) and D. A . G. Brown (Sep. 94) and looking at the tables for the dimensions of the button diameter, spacing, in feed, and cutter blank width, those of both Lammas and Brown agree very closely but the ones by Law are very different. Only Brown gives the formulas for their derivation.

Out of curiosity I ran through the formulas and found that while the one for button diameter gives values that agree with the table, the ones for button spacing and infeed do not. The values from the formula for spacing give figures consistently higher than in the table. But when plugging the numbers into the one for infeed I get a negative value under the root sign (which is impossible). So either I’m reading the formula wrong or there is a mistake in the formula. Anyone else tried to use these formulas and can shed some light on this??

( The way I read the infeed formula is, Cutter infeed F= 1.25 + sqr root of the quantity “ { (D/2)sqr’d - [ D/2 x cos bravo - T/2 + pi/4]sqr’d} - d/2 x sin bravo ".

John

In a "Shop Mechanics Handbook" that I have from about 1958 (published by Science and Mechanics magazine) there is a construction article for a soldering transformer (RSU). It uses a home wound transformer using the laminations from a scrap transformer. It has an output of 100 amps at 5 volts with a taped primary to give two heat levels. The laminations are standard "E" type 5 3/16" by 3 1/2" stacked 2" thick. The primary winding consist of 250 turns of #16 wire tapped at 85 turns and the secondary is 8 turns of either 4 #8 or 6 #10 wires in parallel. Note the primary of this one is wound for an input of 115 VAC and is fused at 6A. The electrode is a 1/2" carbon rod held in a suitably insulated handle. Obviously it could be rewound for 240 volts and any number of taps could be added to the primary for multiple heat levels using various sizes for carbon rods. The heat range can also be regulated by changing the length of the carbon rod extending from the holder ( only if they aren't the copper coated type) . This may not be exactly what you are looking for but should give some idea of the basic construction of one.

John

Edited By John Purdy on 04/06/2018 19:00:46

Ron

I machined the ring by holding in the 3 jaw and facing the back then the front to final thickness and tapering the inner surface to match the wheel tread. Transferred to the mill and cut the slots for the hangers with a 1/8" slitting saw, drilled the holes for the pins, hacks-sawed them apart and cleaned up the ends. Eight brake blocks in less than an hour.

As an added bonus they squeal prototypically when applied.

John

Edited By John Purdy on 07/05/2018 19:57:39

Ron

I know the purists will frown but I made the brake blocks on my riding trolley of aluminum. All eight wheels are braked using compensating rigging and require only light finger pressure on the lever to come to a rapid stop. I had reservations about how long they would last but there is minimum wear after 20+ years. I made a wood pattern as per the photo and cast a ring of 8 shoes in aluminum. Machined all 8 together them cut the individual shoes apart.

John

After reading Neil's lead editorial comments in issue #265 of MEW about the passing of John Wall the designer of the Crayford Focuser I remembered that I had copied the original ME article many years ago intending to make one for my 6" scope. The one I had made when I built the telescope when I was 15 was slightly less than satisfactory. The Crayford didn't get built, though, till a good many years later when I saw an advert in Sky & Telescope for the first(?) commercial one by JMI.
Here are some photos of my version of the Crayford Focuser, including the patterns for the two castings used, and my original 1 1/4" focuser.

Jon

Nick Feast's building of the Q1 ran for 28 installments in ME from Vol. 202, 05 Jun.2009 issue 4353 to Vol. 206, 08 Apr. 2011 issue 4401.

John

Bumper crop in this AM's mail. ME's 4578, 4581, MEW's 267 and in a brown envelope MEW 264 via Royal Mail post dated 18 Apr. Guess there's hope yet! I'm now convinced that the problem has been with our great postal service all along, not My Time Media as I originally thought.

Coelston

Ivan Law's book is available here in Canada from "Busy Bee Tools" and is currently listed on their web site for $29.95, stock number BK170. That's where I got mine and I highly recommend it. Takes a lot of the mystery out of gears and gear cutting.

John

Edited By John Purdy on 26/04/2018 19:28:34

It's now 19 Apr. and I just got ME #4577 (5 Jan.) in the post this AM via Hungary then Czech.   Got #4582 and 83 a week ago so maybe there's hope for the rest of the missing issues as well.  Too bad Canada Post doesn't stamp mail with the date they receive it.   We would then all know where the problem lies.    But I guess that will never happen as it would show just how inefficient they might really be!!!

John

Edited By John Purdy on 19/04/2018 19:01:54

Edited By John Purdy on 19/04/2018 19:06:47

Another update. Just received MEW # 264 in this AMs mail. Inner paper insert post marked Budapest Hungary and a paper label on the plastic wrapper from Prague Cz. Still missing 265.

John

Edited By John Purdy on 13/04/2018 18:39:51

I also received ME 4582 and 4583 together in yesterdays mail. No sign of 77,78, or 81 yet. Nor any sign of MEW 263 or 264, received 266 on the fourth.

John

Just got an e-mail reply from My Time Media to my latest one to them. They are extending my subscriptions to account for my 13 missing issues but won't replace them. That's a lot of good for someone who is working on a project that is currently being described in these issues. I don't want my subscriptions extended I want the missing issues, I paid for them. This is getting ridiculous. Obviously they have no interest in their overseas customers.

John

To correct my last it was the May issue of Sky and Telescope I got on Tues. I got the April issue of Scientific American last week.

John

To address Bandersnatch's comment I just checked the post mark on the envelope from the MEW (#266) I got yesterday and it is from Finland on the paper inner sheet and a label stuck on the plastic bag has a post mark from Belgium!! Checked some of the paper sheets from past MEs and the post mark on the last few are from Budapest Hungary and a while back it was from Prague. So it would appear that there isn't a Canadian distributor and maybe the problem is with Canada Post, but it doesn't explain why there is no problem with getting any of my other mags. As an example on Tues i got the May issue of Scientific American.

John

Just for info I received MEW #466 in this AMs mail here in Comox. Still haven't seen #464 or 465! Have only received ME #s 4279 and 80 since issue 4266 in Dec. I have subscriptions to 4 other mags including ones from the US and the UK and they all arrive within a reasonable time of their issue date. I feel the problem is not with Canada Post,  but with My Time Media's Canadian distributor ( not that I have any love for Canada Post!! )

John

Edited By John Purdy on 04/04/2018 19:39:27

Edited By John Purdy on 04/04/2018 19:41:07

Nick

Further to my last, there was a 4 part series in ME in 2004, issues 4229, 31, 33, and 35 featuring the building of the Wyvern that I found useful. I always find it interesting to see how others approach various machining operations, and sometimes the light goes on, why didn't I think of that???.

John

Nick

Check out my post in the "Drawing Errors and Corrections" section of this forum. I built the Wyvern from the Hemingway set about two years ago and found it a fairly strait forward build, but there are a number of errors and problems in the drawings as noted in my post.

John

Edited By John Purdy on 01/04/2018 19:18:37

Clive

Here in Comox my latest ME is 4576 22 Dec-5 Jan and MEW #263 Jan 18. I'm missing some too.

John Purdy