25point4TPI

Even the elusive 59tpi becomes possible on a crappy gearset with an error of 0.01

58.996361 n[25.000000] n[25.000000] n[60.000000] n[55.000000] n[65.000000] n[65.000000]
58.996365 n[25.000000] n[55.000000] n[60.000000] n[25.000000] n[65.000000] n[65.000000]
58.996361 n[25.000000] n[25.000000] n[65.000000] n[55.000000] n[60.000000] n[65.000000]
58.996361 n[25.000000] n[25.000000] n[65.000000] n[55.000000] n[65.000000] n[60.000000]
58.996361 n[25.000000] n[55.000000] n[65.000000] n[25.000000] n[60.000000] n[65.000000]
58.996361 n[25.000000] n[55.000000] n[65.000000] n[25.000000] n[65.000000] n[60.000000]
58.996365 n[55.000000] n[25.000000] n[60.000000] n[25.000000] n[65.000000] n[65.000000]
58.996361 n[55.000000] n[25.000000] n[65.000000] n[25.000000] n[60.000000] n[65.000000]
58.996361 n[55.000000] n[25.000000] n[65.000000] n[25.000000] n[65.000000] n[60.000000]

Well I for one have no idea what you're on about. Got lost half a million decimal points ago.

Your maths is way out.

58.996361 n[55.000000] n[25.000000] n[65.000000] n[25.000000] n[60.000000] n[65.000000]
58.996361 n[55.000000] n[25.000000] n[65.000000] n[25.000000] n[65.000000] n[60.000000]

No way you can reverse the last two gears and still have the same ratio

Problem is here:

Also some have the same issue with teh first two gears eg

59-23, 50-59, 62-82 can't be the same as

23-59, 50-59, 62-82 can it?

-----------------------------------

59 23-50 59-62 82

23 59-50 59-62 82

first:

(23/50)*59=27.14

(59/62)*27.14=25.82677

82/25.82677=3.17499

3.17499*8tpi=25.3999tpi

second:

(59/50)*23=27.14

(59/62)*27.14=25.82677

82/25.82677=3.17499

3.17499*8=25.3999tpi

It all seems ok to me, (only playing about though)

It looks to me like you are not calculating the ratios correctly (you have got some of the ratios upside down). I get the two setups to give completely different ratios;

59 23-50 59-62 82

(59*50*62)/(23*59*82) = 1.6437

23 59-50 59-62 82

(23*50*62)/(59*59*82) = 0.2498

Neil

Edited By Neil Wyatt on 13/10/2015 13:33:25

Well, I've doubled the result and taken away the first number I thought of, but I still dont get the same answer as you do in the third line down.

Ian P

I've probbly still got the gearsets printout the wrong way round, the maths do work though... once you jumble it about to the right way round...

You need to add the inverse of Pi.

I'll try one:

58.996361 n[25.000000] n[25.000000] n[60.000000] n[55.000000] n[65.000000] n[65.000000]

25 * (25/60) =10.416667

10.416667*(55/65)=8.81410

65 / 8.81410=7.374545

8tpi * 7.374545 = 58.996 TA-DAAAAA!

I always knew I was a genius...

the compound gears are 60in/25out and 65in/55out

Edited By Ady1 on 13/10/2015 14:29:09

Makes much more sense with your suggested correction John. I was beginning to think the mathematics of screwcutting was being played out in Mornington Cresent.

Ian P

.

So ... one of your two answers is correct

What's the relevance of the other one ?

MichaelG.

[still bewildered]

Einsteins maths teacher said he was rubbish at maths too, so I'm in good company

So ... one of your two answers is correct

What's the relevance of the other one ?

It depends which dimension you're in

Edited By Ady1 on 13/10/2015 14:34:42

58.996361 n[55.000000] n[25.000000] n[65.000000] n[25.000000] n[60.000000] n[65.000000]

58.996361 n[55.000000] n[25.000000] n[65.000000] n[25.000000] n[65.000000] n[60.000000]

No way you can reverse the last two gears and still have the same ratio

Yes you can, (the different compound output is turning a different size idler gear on the leadscrew so in certain cases gears can be swapped)

55*(25/65)=21.1538

21.1538 * (25/60)=8.8141

65 / 8.8141=7.374545

7.374545 * 8=58.996tpi

========================

55*(25/65)=21.1538

(25/65)*21.1538=8.1360

60 / 8.1360=7.3745

7.3745 * 8tpi=58.996tpi

=======================

Edited By Ady1 on 13/10/2015 15:07:56

Well at least write the formulae in the correct sequence.

Those two above are identical in sequence and how are we to know what order to take them in.

Einstein might have been rubbish at maths but you are rubbish at logic.

Edited By John Stevenson on 13/10/2015 17:37:30

**LINK**

Edited By Michael Gilligan on 13/10/2015 22:18:11

Afraid i dont know how to do the link things like Michael G [ and others ], some might like this though.

Pagagnini - Pachelbel"s Canon in D , You tube. oops way of topic ,sorry Ady.

bodge

It gets worse...

I wanted to drill holes or cut teeth for weird tooth numbers with limited gearsets using the banjo/headstock as a division tool and I may have cracked it

A 59 tooth gear with 0.0002 error

Gearset 20 25 30 35 40 45 46 50 55 60 63 65

The first gear, 20, is irrelevant, all that matters is if it's moved 59 times and the compund set moves the final gear, (which in case one is a 46tooth) 59 times AND completes a proper 360 degree revolution then we have a winnah

As usual my outputs are jumbled up

0.999856 n[20.000000] n[30.000000] n[46.000000] n[55.000000] n[46.000000] n[46.000000]

Soooo...

the 20 is irrelevant, then 46in 30out and 46in 55out to a final spindle cog of 46

59 clicks on the detente is (using the 20 or anything you want as an idler)

(59/46)*30= 38.478 clicks

(38.478/46)*55=46.0066 clicks on a 46.0000 toothed final gear

Full results below (edited to two gearsets)

0.999856 n[20.000000] n[30.000000] n[46.000000] n[55.000000] n[46.000000] n[46.000000]
0.999856 n[20.000000] n[55.000000] n[46.000000] n[30.000000] n[46.000000] n[46.000000]

Might be wrong of course but it's looking good so far

Edited By Ady1 on 16/10/2015 16:43:22

How can the PRIME driver be irrelevant ??

Idlers yes, drivers and driven, no

It's a 20 pretending to be a 59

It's all kosher, honest guv, on my life.

My initial interest was for the Westbury dividing head which fits onto the milling slide/saddle of your lathe

The first cog is only an idler in this case, then 2X compound gears and the final spindle gear

Can't remember which book it was in... Hemingway do a kit

edit:

If it is relevant, then swap the 20 for a 46 and do 59 divisions

edit2 It wasn't westbury, it was the sparey one I was thinking of, in "the amateurs lathe"

Edited By Ady1 on 16/10/2015 17:54:12

I think you lost me when you wrote the third word in your first post..................................

There are these icons above the area where replies etc are typed out and lo hover the cursor over them and what they do pops up. Click one if it's the right one and it actually allows you to do it, links can be pasted in.

John

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