What Did You Do Today (2016)

[Michael GilliganParticipant @michaelgilligan61133]

This series of 'National Gepgraphic' books has been promoted on TV recently: **LINK**

http://ourmathematicalworld.co.uk/uploads/20161219/MathematicalWorld_F0.pdf

I bought issue_1 today, which looks good value at £1.99

… But be warned: issue_2 is £5.99 and the 'regular' price will be £8.99

That would make for an expensive set !!

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 29/12/2016 20:55:40:

The main effect is latitude

Neil.

.

… I am resisting the urge to indulge in pedantry

[Colin WhittakerParticipant @colinwhittaker20544]

Continuing on the dead weight tester pressure calibration story …

Besides making a correction for latitude there is also a correction for altitude as the atmospheric pressure drops. For example, back in the early 1990s, 4,500 ft up in the Southern Highlands of Papua New Guinea, I found I'd spent 2 years calibrating my strain gauges 2 psi high (or was it low?).

Happy new year..

[Bob RodgersonParticipant @bobrodgerson97362]

Andrew,

I was having trouble with Gearotic and thought that maybe this might answer some of your problems with it. It followed problems that I had with the programme running on my laptop.

Hi Bob:



I figured it might have been. Rule generally is 2.5D things like spur gears can be made on the 3d workbench or in 4th axis, helicals, knuckles and such on 4th axis only,

and bevels only in stl outputs.. nothing will machine them.

[Brian OldfordParticipant @brianoldford70365]

Posted by Les Jones 1 on 29/12/2016 18:04:59:

Hi Bob,
I think the 41 tooth should be a 42 tooth so the overall ratio is 2:1

Les.

I'm not too sure that is correct. If the first meshing pair were 20 driving a 21 (to get a hunting tooth) the second pair would need to be 21 driving a 40. That would also produce the hunting effect and an overall 2:1 reduction for the camshaft.

[Les Jones 1Participant @lesjones1]

Hi Brian.
I have miss read Bob's post. I read it as 21 driving a 20 and a 20 driving the 41. The way it is written I calculate the "41" needs to be 38.0952380952381 teeth so something is not right.

Les.

[neville rigg 2Participant @nevillerigg2]

Hi Brian

I seem to remember a similar situation about 50 years ago with a KSS Velo, may be wrong but it rings a bell,

surprising what pops out of the memory.

Neville

[Brian OldfordParticipant @brianoldford70365]

Posted by Les Jones 1 on 30/12/2016 09:41:59:

Hi Brian.
I have miss read Bob's post. I read it as 21 driving a 20 and a 20 driving the 41. The way it is written I calculate the "41" needs to be 38.0952380952381 teeth so something is not right.

Les.

I'm given to believe 38.0952380952381 might be a tad trick to cut.

[Anonymous]

Posted by Bob Rodgerson on 30/12/2016 08:51:39:

Andrew,

I was having trouble with Gearotic and thought that maybe this might answer some of your problems with it.

………….and bevels only in stl outputs.. nothing will machine them.

Thanks Bob. If I understand correctly Gearotic only outputs data for bevel gears as STL files? Presumably for 3D printing. Sadly that's not much use for me. I've been looking at my CAM program again this morning. It turns out that I need a 0.8mm cutter, not 1mm, to clean out the roots. For some reason 0.8mm cutters are "How much!?" expensive. So I can either use a 1/32" cutter or reduce the face width of the bevel gear so that I can use a 1mm cutter.

Andrew

[Bob RodgersonParticipant @bobrodgerson97362]

Hi Andrew,

Thats the way I read it too. Definitely dissapointing.

I was wondering if any of the miniature burrs would be as small as 0.8 mm If they are they would be worth a try.

[Bob RodgersonParticipant @bobrodgerson97362]

Re Gear Ratio,s I am not too concerned because I have a set of hears that I can count the nimber of teeth on before cutting any metal. The odd number of teeth in the 2-1 overall ratio is to give the gears a hunting tooth to reduce wear.

[Anonymous]

I'll have a look at burrs, thanks.

I think the idea of a hunting tooth is to even out wear, rather than reduce it per se. For two gears with the same number of teeth the same pair of teeth will engage once per revolution. The numbers 20 and 21 have no common factor. So I think that means that the same pair of teeth will only engage every 20×21=420 revolutions, thus evening out the wear.

Andrew

[Bodger BrianParticipant @bodgerbrian]

Having got my new indoor workshop / man-cave into some sort of order, I dug out my first foray into model engineering – my Benson's Engine (a la Anthony Mount). It's a long way from being finished and isn't in too good a condition, having been sat in a damp outside shed for the past 8-9 years, so the first thing is to clean it up & reacquaint myself with what I've done, what I've half-done, what I haven't done & what I need to re-do. I hope the picture doesn't show too many machining marks, bodges & mistakes

Brian

[HacksawParticipant @hacksaw]

I tried to cut a thread on me lathe.. not so scary as i thought , but it was rubbish ..

I'm going to read up a bit on gears and changing them .Doing it without a dial isn't easy with the ratio's that are fitted .Took ages to get everything to line up again before every pass .,

[Gray62Participant @gray62]

Took delivery of my next tooling project, a Dynamic tool post grinder from Hemingway Kits.

[Bob RodgersonParticipant @bobrodgerson97362]

Andrew,

try the following for Micro Mills at seven Quid for 10 they are expensive. that well known auction site has them available for four quid or so.

https://www.eternaltools.com/miniature-carbide-end-mills-slot-drills

I know I bought some off ebay a while back and they are OK and will probably do what you are needing them for.

Bob

[JasonBModerator @jasonb]

Posted by Hacksaw on 30/12/2016 17:22:37:

I tried to cut a thread on me lathe.. not so scary as i thought , but it was rubbish ..

I'm going to read up a bit on gears and changing them .Doing it without a dial isn't easy with the ratio's that are fitted .Took ages to get everything to line up again before every pass .,

You could try leaving the leadscrew engaged all the time. At the end of the cut stop the lathe and retract the tool then either run in reverse or rotate chuck backwards which will move the carrage back towards the tailstock. Once at the right place wind the tool back in plus the depth of the next cut and away you go. This method often has to be used when cutting imperial on a metric machine and metric on an imperial one

[JasonBModerator @jasonb]

Please use the 2017 thread from now on.

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