Gear ratios and alternatives

[Oompa LumpaParticipant @oompalumpa34302]

So Boys and Girls, I am just a bit uncertain. I would be the first to admit that I didn't receive an 'A' Star in maths.

I have a good boxfull of changewheels here but I am lacking a 75 tooth wheel. Have everything else and in some instances multiples, but I need to cut a 1mm pitch thread and don't have the right wheels to follow the pictures

Here is a pic of the various combinations and I would be very grateful if someone could give me some alternative combinations to cut the 1mm pitch I need. Thanks very much.

graham.

[Oompa LumpaParticipant @oompalumpa34302]

[Oompa LumpaParticipant @oompalumpa34302]

Just in case the actual layout is helpful, here it is:

[Les Jones 1Participant @lesjones1]

Hi Graham,
If you have 40 tooth and another 60 tooth you could replce the 50 tooth with a 40 tooth and replace the 75 tooth with a 60 tooth. If you could give a list of gears that you have it would help us to work out an alternative.

Les.

[RichardSParticipant @richards31161]

If I have picked up the right chain you need:

75/50 and 80/60 and are missing the 75.

75/50 is 1.5:1 so a 60/40 will give the right ratio.

The iffy bit is if the gears will mesh.

[JasonBModerator @jasonb]

If its anything like the other imported lathes you will only have one 60T gear so that may not be an option

As Les says can you list the gears you have including whats already on the banjo to give fine feeds and what the number of teeth are on the spindle, probably 40T as that can't be changed

[Oompa LumpaParticipant @oompalumpa34302]

Les and Richard, thank you both for this. It has confirmed my thinking (didn't need to break anything this week) and I have both of those combinations so no problem then.

I see what you mean about the meshing bit Richard so I will go lay them out and see. I will also make a listing of all the gears I have for reference.

graham.

Ah, yes – two 60 tooth gears. I will go check.

Edited By Oompa Lumpa on 09/03/2015 19:25:51

[Oompa LumpaParticipant @oompalumpa34302]

So, I have the following wheels:

1×85, 3×80, 1×72, 1×71, 1×70, 2×60, 1×50, 1×45, 1×40, 1×33, 1×30, 1×27, 1×25 and 1×20

I didn't count the gear on the spindle Jason but it is the same as the Warco 280 I think so will be 40 in all likelihood but if this s a deal breaker I will go count the teeth.

Thanks again.

[John Stevenson 1Participant @johnstevenson1]

30 in place of 60 on Z2 then select B instead of A

 

Edit to get me A,B and C right

Edited By John Stevenson on 09/03/2015 19:55:01

[Les Jones 1Participant @lesjones1]

Hi John,
If my understanding is correct the 60T is only an idler between the spindle gear and the 80T so changing it would have no effect.

Les.

[Oompa LumpaParticipant @oompalumpa34302]

Posted by John Stevenson on 09/03/2015 19:53:54:

30 in place of 60 on Z2 then select B instead of A

Edit to get me A,B and C right

Edited By John Stevenson on 09/03/2015 19:55:01

Ahh! Just had one of those "lightbulb" moments. Thank you very much for that. Some days the Bleedin' obvious isn't.

graham.

[Les Jones 1Participant @lesjones1]

Hi Graham,
Another possiblility. Replace the 50T with a 60T and replace the 75T with a 45T and change the gearbox to position "C"

Les.

[John Stevenson 1Participant @johnstevenson1]

Posted by Les Jones 1 on 09/03/2015 20:00:41:

Hi John,
If my understanding is correct the 60T is only an idler between the spindle gear and the 80T so changing it would have no effect.

Les.

Sorry, yes Les you are correct, I though just from the chart the Z2 was the driver.

So in this case swap the 80 on Z3 for a 40 then do the A & B swap

[Les Jones 1Participant @lesjones1]

Hi John,
Graham does not have the 75T to go on the gearbox input shaft.
At first I made the same assumption as you did from looking only at the first table.

Les.

Edited By Les Jones 1 on 09/03/2015 20:30:10

[John Stevenson 1Participant @johnstevenson1]

Sod it need to learn to read.

 

Ignore what i have written, everyone else does anyway

 

Edit,

Why have you got a 71 and 72 ? can't see them listed, have you tried counting the teeth on these just to be certain ?

Edited By John Stevenson on 09/03/2015 20:45:58

[JasonBModerator @jasonb]

Another alternative is to use the 0.75/1.5/3.0 (2nd right) layout but substitute a 40T on Z4 which will give 0.5/1.0/2.0

Edited By JasonB on 09/03/2015 20:43:53

[Les Jones 1Participant @lesjones1]

Yet another possible solution. 60T gear on gearbox input shaft (L) Gearbox set to "C" Any two gears on intermediate shafts just as idlers. (Just one gear on each shaft.)

Les.

Edited By Les Jones 1 on 09/03/2015 22:31:07

Edited By Les Jones 1 on 09/03/2015 22:33:46

[Oompa LumpaParticipant @oompalumpa34302]

Posted by John Stevenson on 09/03/2015 20:41:26:

Why have you got a 71 and 72 ? can't see them listed, have you tried counting the teeth on these just to be certain ?

Edited By John Stevenson on 09/03/2015 20:45:58

Probably for the same reason I had no 45 or 75 gear in the box! My fault, I grabbed the nearest box without asking if it was the right one. 

I have to say however that the service I received from Chester has been exemplary. I noticed the 45 tooth missing and Tony sent me one by next day courier. I saw the 75 missing late in the day and I will collect that at the next Chester open day in June where I will go collect my new Mill.

graham.

 

 

Edited By Oompa Lumpa on 10/03/2015 09:29:14

[Les Jones 1Participant @lesjones1]

Hi Graham,
Did any of the suggestions fit on the banjo and work ?

Les.

[Oompa LumpaParticipant @oompalumpa34302]

Several combinations fit Les but since my "Eureka" moment last night when the multiplication factor of the gearbox hit me I have been thinking about some of the combinations that I commonly use. Come on – who actually enjoys messing about putting changewheels on and off the lathe?

I am trying to work out how to create a couple of clusters – I have a couple of extra spindles I have just made for the banjo – so that I can just ready them and swap them about as I need. As opposed to dismantling the whole banjo every time I need a different thread.

graham.

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