What did you do today? (2014)

[Oompa LumpaParticipant @oompalumpa34302]

I have repaired and painted the living room door today. One of my dogs has worked out how to open doors but the next step is to teach him how to do this gently!

graham.

[Bob RodgersonParticipant @bobrodgerson97362]

Hi Jason,

like the flat twin, very nice piece of work. I have built three of them to my own design, the last one was a 200 cc petrol fuelled monster. I have found with all of them that icing of the manifold is common, particularly on warm humid days. If you intend using it in model aircraft I would consider twin carbs with short inlet tracts.

Bobn

[Martin CottrellParticipant @martincottrell21329]

Posted by JasonB on 25/08/2014 13:26:39:

Still need to make an engine mount and order an appropriate prop so will be a week or two before its time to dance.

Another fine looking piece of work Jason. I can't believe how quickly you seem to produce these engines! Are you planning a build thread either here or elsewhere?

Regards Martin.

[JasonBModerator @jasonb]

I was building that along with the Monitor so it may seem like I do them quickly when really the two got finished at about the same time. I think first swarf was made in early April.

I did mention to Diane that I may do it for ME as its based on Malcom Stride's Bobcat/Jaguar so nice to continue what he started but will only cover the different parts, (don't think the mag could take the 200+ photos) failing that its likely to be on MEM, here or both.

J

PS prop is ordered and engine mount started

[Clive HartlandParticipant @clivehartland94829]

Just a quick note about the Rosetta probe, the ESA scientists have deliberated about landing places on the Comet and decided on 5 spots. There are a set of photos showing the locations on the Comet. The landing will not be until November.

Clive

[Boiler BriParticipant @boilerbri]

North Wales model engineering finished the out loop and enjoyed a weekend of steaming!

Brian

[Raymond Sanderson 2Participant @raymondsanderson2]

JasonB thats a piece of art look forward to seeing the completed work when prop done.

[StovepipeParticipant @stovepipe]

JasonB,

A very handsome and impressive piece of work, sir. As others have said and commended it.

Dennis

[BubbleParticipant @bubble]

This took me a bit longer than a day, but I finished today

Gears for the oil pump on my Morris 8 engine.

The gears are 11DP 25 degree pressure angle in EN8. They were generated using my shaper with a rack-form tool and a fixture based on an article by "Duplex" in ME many years ago. The gear blank is rotated as the rack tool is moved laterally, using a wire drive onto a disc of a diameter equal to the pitch circle minus the wire diameter. This generates the correct involute, none of that compromise shape that you get with a shaped gear cutter. The calculated pressure angle from measurement of the old (worn out) gears was 30 degrees but this gave unacceptable undercutting of the tooth root, a problem often found on clock pinions.

11 teeth, 20 cut-increments per tooth,50 strokes per cut, X2, plus several experiments made for about 25000 shaper strokes. I made an abacus to keep track. Good job I'm retired!

Jim

[lancelotParticipant @lancelot]

Hi All…engine work is on temporary hold for a bit…I am stripping down the ''speed 10 '' Myford to get it out of the massive steel cabinet it is in…i reckon it will almost double the room I will have …I will build a workbench to mount it on…at moment all that is left to get out of the shed is the bare steel stripped down cabinet…Getting it out of the shed s a teaser…the shed is actually built round the unit…Funny until you have to get it outthere is no height clearance allowing us to lift it and wangle it out… there seem to be two options …cut it up smaller…''big job.fire hazard '' remove end of shed…feasible??? watch this space…

John.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bubble on 26/08/2014 17:52:20:

This took me a bit longer than a day, but I finished today

Gears for the oil pump on my Morris 8 engine. < etc. >

.

A very nice job, Jim

MichaelG.

[DrDaveParticipant @drdave]

Having pushed my luck with parting off a big lump of cast iron with my new rear tool post, I must admit that I chickened out of the power feed malarkey tonight. However, both the HSS tool & KIT-Q-CUT worked well on a 16mm steel bar. Ah, parting is no longer such sweet sorrow!

[rooferParticipant @roofer]

Making 1 good 2 KVA generator out of 2 machines…swapping bits and crank from a Honda 5.5HP and ended up with a very good twin outlet 110V machine. Bought 2 of em for £20 from my local scrapyard.All this after a days roofing mind

[Anonymous]

Jim: Excellent work, lovely looking gears. It's not a method I've used, so I have a question. Presumably the teeth flanks are actually composed of a series of straight lines, the fineness of which is dependent upon the linear/rotary increment per stroke of the ram?

Intuitively I would have expected the issue of undercutting to be less of a problem as the pressure angle increases; have I misunderstood?

Regards,

Andrew

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by Andrew Johnston on 26/08/2014 23:08:18:

Intuitively I would have expected the issue of undercutting to be less of a problem as the pressure angle increases; have I misunderstood?

That's my understanding as well. When I made the cam drive pinion for my 10cc side valve aero engine I made 30° PA gears to minimise the under cutting (all knowledge gained from Ivan Law's splendid book). Perhaps the wear on the original gears had changed the apparent PA. 25° is still greater than the normal 20° , or maybe even 14.5°, of the original. Whatever, the effort was definately worthwhile: they look terrific. Very nice photography also.

Actually, thinking about it, perhaps a bit of undercutting may not be a bad thing if these gears actually drive the oil – a bit like the vanes on a Rootes blower?

Thanks for sharing,

Rod

Edited By Roderick Jenkins on 27/08/2014 00:30:52

[Bill PudneyParticipant @billpudney37759]

Nothing like as interesting as Bubbles beautiful gears, but a maybe cautionary tale. I'm in the middle of reorganising my workshop/shed and had rescued some bits of 40mm x 40mm x 6mm steel angle from a redundant rainwater tank stand. After spending 25 years plus holding the rainwater tank up off of the ground they were a bit tatty with some patches of rust. I decided to derust/degrot them with a rotary wire brush, of course I wore some safety goggles. Just as well that I did, because after spreading rust dust and paint dust all over the place, when I was cleaning up I found a 5mm length of wire embedded in the safety glasses. As far as I could tell the wire had penetrated 1 to 1.5mm. It was right in the middle of my line of sight, so would probably have penetrated my eye…………….

I know that we all wear safety glasses all the time, but it pulled me up a bit quick.

cheers

Bill

[MuzzerParticipant @muzzer]

Wow! One of those ooh er moments!! Well held!

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Bill Pudney on 27/08/2014 04:35:30:

Nothing like as interesting………………………………. I decided to derust/degrot them with a rotary wire brush, of course I wore some safety goggles. Just as well that I did, because after spreading rust dust and paint dust all over the place, when I was cleaning up I found a 5mm length of wire embedded in the safety glasses. As far as I could tell the wire had penetrated 1 to 1.5mm. It was right in the middle of my line of sight, so would probably have penetrated my eye…………….

I know that we all wear safety glasses all the time, but it pulled me up a bit quick.

cheers

Bill

 

Hi, I personally would not dream of using a rotary wire brush, or any kind of grinding discs etc, without eye protection, even for a quicky. I also prefer a full face visor as those bits will sting your face and they give better around vision and don't steam up so much. I have found little bits of those wire brushs stuck in my clothes when getting dressed after they have been washed, they do seem to get everywhere.

Regards Nick.

Edited By Nicholas Farr on 27/08/2014 07:28:30

[Clive HartlandParticipant @clivehartland94829]

I have always when using wood splitting chisels ground off the 'Curl' on the impact end. Then, watching someone doing a chisel cutting job, a piece flew off the impact end and embedded itself in my lower leg! Not thinking much about as it only bled a little I put on a plaster and that was it! Some years later I felt something sharp on my skin on the leg and I found a sharp piece of metal sticking out, yes, the bit that flew off the chisel! I carefully got it out and it was a 1/4" by 1/8" and curled up so i knew where it had come from!

Clive

[David ColwillParticipant @davidcolwill19261]

Clive
Like you I always grind the curl off chisels but have to confess that I thought bits flying off was a bit of an old wives tale. Glad to know I’ve been doing something right.
Regards.
David.

[OuBallieParticipant @ouballie]

Jim,

Ditto what has already been said re the gears.

Which ME Issue are you referring to please?

Just in case I need to make any gears for my classic cars.

Geoff – Deciding what to do.

[Russell EberhardtParticipant @russelleberhardt48058]

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

[BubbleParticipant @bubble]

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

[BubbleParticipant @bubble]

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

[JasonBModerator @jasonb]

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)

[Author]

Posts