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What did you do today? (2014)

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Bubble27/08/2014 14:24:21
75 forum posts
6 photos

Hello all

Geoff; the original article was in ME September 14th 1950. If you don't happen to have that issue to hand (!) it is reprinted on the website of the New England Model Engineering Society (neme-s.org)

Russel: I wish! My gears were chewed up, I think it had been run with no oil at some point. The engine now has a rebore and crank grind (not by me, Hargreaves Engineering in Carmarthen, excellent old fashioned Engineers sadly now defunct), but I did the rest including reground camshaft bearings, line bored bronze camshaft bearings in block, head reground, new valve guides, crankshaft rear seal etc. You may know that the camshaft centre bearing on these engines was prone to wear, was the first port of call for the oil from the pump and was machined in the block, not lined.

Andrew, Roderick: I think you are right, looking back at my notes (from over a year ago when I started experimenting), it was the 20 degree angle that gave root undercut for gears with low tooth count, 30 degrees gave teeth that were too narrow on the tips and in the root. Gear pumps have different tooth form requirements to transmission gears, needing a good volume in the root area to carry the oil around, and a wide tip to minimise leakage from tooth to tooth, but the stresses are low so no requirement for a large root radius. My try-outs were just three teeth and axially short so not too time-consuming to do. The rack-shape tool is very easy to make and modify.

Andrew: Correct, the tooth flank is a series of flats. Each flank had about 25 increments of cut (final strokes were three repeats of same cut) and feel very smooth. Under my low power microscope you can't see actual flats, just longitudinal planing marks. The gears rotate smoothly and no doubt will improve with running.

Thanks all for your interest.

Jim

Bubble27/08/2014 16:00:15
75 forum posts
6 photos

Hello all

Further to my gear post, the ME article title was "Gear Cutting with the Shaper" and the author was "Base Circle", not "Duplex"

Jim

JasonB27/08/2014 16:15:12
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For anyone who can't picture how this method of gear cutting works there are some photos on Baily's site that show a full size machine doing teh job (4th row downwards)

roofer27/08/2014 19:30:26
21 forum posts
Posted by Russell Eberhardt on 27/08/2014 11:33:04:
Posted by Bubble on 26/08/2014 17:52:20:
Gears for the oil pump on my Morris 8 engine.

Great work. Never had to do that on my Morris. Just grinding the cover plate flat to remove the wear brought the oil pressure back.

Russell.

Edited By Russell Eberhardt on 27/08/2014 11:34:17

Edited By Russell Eberhardt on 27/08/2014 11:37:21

Done this to an old Range Rover classic with great sucess too.

Andrew Johnston27/08/2014 22:47:30
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5736 forum posts
661 photos

Jim: Thanks for the elucidation on the method. I'd agree that 25 facets on an 11DP gear would be pretty much invisible. I had a trawl through my gear design books and found the following equation for the minimum number of teeth before undercutting occurs when using a straight sided hob, it depends only upon the pressure angle. The second equation was found elsewhere, but is mathematically identical, albeit in a more elegant form:

undercut.jpg

Regards,

Andrew

Muzzer28/08/2014 04:48:13
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2904 forum posts
448 photos

Whether or not you use Solidworks (or even use any form of CAD at all), here's an interesting video showing how to construct a gear model. Using parameters, the module size and number of teeth can be dialled in and the rest adjusts appropriately. This approach could be applied to DP (imperial) gears with minor changes.

It takes a little time to build up the model but about 10 mins in, the tooth construction is apparent.

Murray

Raymond Sanderson 228/08/2014 07:42:01
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449 forum posts
127 photos

I went for a spill off my workshop stool.
One of the ally feet broke and I found another cracked latter on when checking.
Its just 2 weeks since I put new wheels on and when doing so didn't notice any signs of cracks.
I was sitting at full height as its a draughtmans stool and toppled over backwards sort of, some injury nothing major a twisted knee and ankle and hurt pride.

I have a spare stool so can head back out tomorrow.

dscf7924.jpg

Michael Gilligan28/08/2014 07:51:35
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16644 forum posts
725 photos

Raymond,

Please forgive me if this sounds critical; but I suspect that your improvements may have been a contributing factor.

... Those fixings for the castors look non-standard for a stool, and may have created some "stress-raisers" [ in the mechanical, rather than the emotional sense ]

MichaelG.

Oompa Lumpa28/08/2014 08:51:00
888 forum posts
36 photos

Irrespective, don't you just feel like a Balloon when something like this happens!

I really need to get myself something along the same lines but without the wonky foot

graham.

Ian S C28/08/2014 14:19:25
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7468 forum posts
230 photos

The chair I'm sitting on now has similar geometry, it doesn't seem to have an excess of metal, probably about 3 mm thick, with some webs across the inverted U shape. The castors are pushed into holes in the die casting, and drilling these through would indeed weaken the structure. On closer inspection my chair will not fail through metal fatigue, it's made of plastic!       Ian S C

 

 

Edited By Ian S C on 28/08/2014 14:23:16

Raymond Sanderson 228/08/2014 23:38:41
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449 forum posts
127 photos
Posted by Michael Gilligan on 28/08/2014 07:51:35:

Raymond,

Please forgive me if this sounds critical; but I suspect that your improvements may have been a contributing factor.

... Those fixings for the castors look non-standard for a stool, and may have created some "stress-raisers" [ in the mechanical, rather than the emotional sense ]

MichaelG.


Michael I've been using the draughtsman stool now for some 7 yrs it has not had an easy life goodness knows how old it was before I got it 2nd hand. I know of many who had suffered similar fates and worse during the years draughtsman used them. The place I buy my castors from have done the same with their plastic office chairs much lower of course.

The stresses I put the chair under moving about the workshop with the alloy as thin as it is although well webbed structure it has been a good chair.

Glad i have a spare the same.

Raymond Sanderson 228/08/2014 23:43:18
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449 forum posts
127 photos
Posted by Oompa Lumpa on 28/08/2014 08:51:00:

Irrespective, don't you just feel like a Balloon when something like this happens!

I really need to get myself something along the same lines but without the wonky foot

graham.

Graham I wish I had been a balloon the fall would have been a lighter one LOL

As I just mentioned to Michael its been in use now over 7yrs the new castors just installed 2 or 3 weeks gone and no sign of cracks the old castors had worn down enough so the breaks/locking devices were not holding. its a bugger trying to transfer to a moving stool.The spare stool with older type castors LINK

Raymond Sanderson 228/08/2014 23:50:06
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449 forum posts
127 photos
Posted by Ian S C on 28/08/2014 14:19:25:

The chair I'm sitting on now has similar geometry, it doesn't seem to have an excess of metal, probably about 3 mm thick, with some webs across the inverted U shape. The castors are pushed into holes in the die casting, and drilling these through would indeed weaken the structure. On closer inspection my chair will not fail through metal fatigue, it's made of plastic! Ian S C

Edited By Ian S C on 28/08/2014 14:23:16

Ian it didn't snap/crack at the hole but about 10mm away. I won't say the castors didn't add to it but after 7yrs use by me in a harsh environment.

The plastic base ones well like the wheels they don't last long and I have seen them snap the whole arm off anywhere from the castor area right to the centre join. That use has been in offices by lighter persons than myself.

I have had thoughts of making a tube frame and new centre of steel as this is a long term situation for me.

There are wheelchair type situations which raise you up by elec/hydraulics cost tho is so much out of reach its cheaper to buy a new small car.

"Bill Hancox"29/08/2014 02:12:48
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256 forum posts
76 photos

Ray

Good Gracious. You must be made of tough stuff. That incident could have finished a normal man like this unlucky bloke.http://www.youtube.com/watch?v=RAwYq7Acc3o

Bill

Raymond Sanderson 229/08/2014 03:13:35
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449 forum posts
127 photos

Bill LOML was just as close at the time helping clean up from the mornings wood turning. Good job all the hammers wee out of reach.

Every time I see that clip it reminds me of my parents in reverse rolls not quite but I bet dad wished he could have done similar LOL.

Clive Hartland29/08/2014 10:14:07
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2617 forum posts
40 photos

This has been an interesting week, we had Monday off ( Bank Hol) so on Tues,. morning i went to work and the place was locked up and I sat for an hour reading my paper and then left to go back home as it seemed there was not going to be any one else coming. Wed. morning wifey gets a phone call saying the Boss man had lost the sight in one eye. Thur. morning i go in and the other lad is there and he has had a call saying that the eye injury was where the eye had gone 'Milky' . So now I will have to wait till Mon. to get the full story. Needless to say we also heard that he was shunted around from the eye hospital to A & E, Anything to elongate the waiting times. I will come back on this as soon as I hear from the horses mouth as to what happened. You could not meet a nicer chap than Peter, he has had all sorts of family problems and just soldiers on doing what he has to do.

Clive

Michael Gilligan29/08/2014 20:32:08
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16644 forum posts
725 photos

Bought an interesting little "Jason" lathe today:

I believe this was the final design by Brian Perris, but [for whatever reason] was not the version that eventually morphed into the Cowells.

If anyone knows the last chapter in the history of Perris; do please share it.

MichaelG.

.

Edit: added hyperlink

Edited By Michael Gilligan on 29/08/2014 20:34:21

Neil Wyatt29/08/2014 21:12:09
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Moderator
18322 forum posts
718 photos
77 articles

Very neat Michael, rather more sophisticated than the Adepts though!

Did you find this page on Tony's website?

Neil

Michael Gilligan29/08/2014 21:39:16
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16644 forum posts
725 photos
Posted by Neil Wyatt on 29/08/2014 21:12:09:

Did you find this page on Tony's website?

.

Yes, thanks Neil ... I had seen that page, and also have a dim recollection of meeting Mr Perris at one of the ME Exhibitions.

It may have something to do with the several other parties that were involved at the time, but I would be very interested to know why Cowells didn't develop the Jason design [to my eye, it has great promise].

MichaelG.

.

P.S. ... If I've missed something in Tony's write-up, do please point me to it.

lancelot29/08/2014 21:47:36
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63 forum posts
4 photos

Hi all...measured up cabinet cut a section of shed wall out ''double skinned '' so quite a job...removed cabinet through hole ...repaired and strengthened hole with security items...If using ''GORILLA GLUE'' do what it says on the tin ''WEAR GLOVES'' .

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