Gear indexing problem

[Klegenheim]

Hoping that everybody out there had a Happy Christmas!

I am thinking about building a skeleton clock and at this point have not got much further than just that! The reason is that I will have to cut a main wheel of 290 divisions. The plans call for a 60:1 dividing head which with a 29 hole plate and indexing every 6 holes would achieve this. The problem is that I only have a 72:1 worm gear. Clearly I would like to avoid the cost of buying or time in making a 60:1 worm gear etc etc.

Are there any ideas out there as to how this could be solved with my present equipment?

 

[Charles Lamont]

The problem is that while 290 and 60 are both divisible by 10, allowing the use of a 29-hole plate, the highest common factor of 290 & 72 is 2, meaning you would need a 145-hole plate, which unfortunately does not get you much further forward. If you have a lathe with change wheels it might be possible to set up a train that would give 145 divisions. Altenatively, have you a means of compound indexing, in which there is a second stage to incrementally rotate the division plate?

 

[Gordon]

Could you use this method?

http://oxtool.blogspot.com/2013/11/5c-spindexer-indexer.html

I have used this on larger 48DP gears. I don't know about clock gears.

 

[chucketn]

Are there any ideas out there as to how this could be solved with my present equipment?

Where are you located? There might be a hobbyist close to you that can help.
For example, I have an Arduino based setup for my RT that could generate the 290 hole plate, or any other required.

Chuck

 

[kvom]

If you imagine a plate with 1/8" diameter holes separated by 1/8", then the circumference of a 145 hole plate would be approximately 36" or 11.5" in diameter. Likely much too big for any dividing head.

Might it be possible to make a disk with 5 separate rows of 29 holes, each offset appropriately?

 

[xpylonracer]

Thanks for the link Gordon, certainly a simple method to overcome the diameter of indexing wheel problem.

Emgee

 

[Wizard69]

You could try hooking up a stepper and electronically indexing the drive shaft.

 

[MichaelWilliams]

Gear drive the input shaft so that the actual 72 tooth indexing wheel is made to work like a 60 tooth wheel . You can then use 29 hole plate and simple indexing .

Required ratio is 72/60 so 36/30 may be easiest practical combination .