Hypocycloidal gears

[Mike BrettParticipant @mikebrett89695]

Having just purchased a nice internal ring gear I was thinking of building a version of Elmers hypocycloidal engine. Would I be right in thinking that the internal cog has to be exactly half the size of the external ring gear. Only the small cog that I got with the ring gear is only about a 1/4 of the large gear.

Mike

[Mike BrettParticipant @mikebrett89695]

Elmers Engine

[JasonBModerator @jasonb]

Small one should be half the number of teeth of the larger gear.

[Mike BrettParticipant @mikebrett89695]

I have just tried to cut the internal gear for the ring I have and failed miserably. To be honest I do not have the skill or the equipment for this task. The ring I have is about 3 inches diameter with 50 teeth, so I need a 25 tooth 1 1/2 inches diameter gear. Is there anybody out there that could cut me one for a fee , or my project does not get of the ground.

Cheers Mike

[JasonBModerator @jasonb]

If you know the spec of the gear eg DP or MOD so should be able to get one from the likes of HPC for about £20

[John Stevenson 1Participant @johnstevenson1]

If it's a Module gear then Beltingonline is very, very reasonable for price.

If it's DP then they are more in line with HPC

25 tooth 1.25 MOD is £5.48 but the same in DP is over £20

[John HaineParticipant @johnhaine32865]

When you say about 3 inches and 50 teeth, is that internal diameter? For a module gear (i.e. metric) 3 in = ~75 mm; divide by 50 would give module 1.5 which sound reasonable and standard. But 3 inches/50 teeth is 16.67 DP, I'm not sure that is so standard (JS would know better).

John, where did your 1.25 mod come from?

[Mike BrettParticipant @mikebrett89695]

No idea what you mean by DP or MOD, there are no markings on the ring. If someone was going to make me a cog I intended to send them the ring to work from. Perhaps it would be better to buy both as a set, if I new where to get them.

Mike

[JasonBModerator @jasonb]

You could get a ring gear from HPC and a cheaper spur gear from JS's link

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mike Brett on 29/04/2016 14:42:47:

No idea what you mean by DP or MOD, there are no markings on the ring.

.

Put it on a flatbed scanner, and post the image here; together with a measurement of the diameter [for scale].

I'm sure that, between us, we can work out what DP or Module it is.

MichaelG.

Edited By Michael Gilligan on 29/04/2016 15:18:37

[John Stevenson 1Participant @johnstevenson1]

Posted by John Haine on 29/04/2016 14:07:14:

John, where did your 1.25 mod come from?

Just a rough guess at a gear 'about' the right size for pricing purposes.

Until the OP gives accurately measurements no one can help accurately.

[Mike BrettParticipant @mikebrett89695]

Measurements : Between the teeth (peak to peak across the circle) 77mm. Between the teeth (valley to valley across the circle) 83mm. Outside diameter 114mm.

[Neil WyattModerator @neilwyatt]

With internal gears the calculations are essentially as if you were measuring a normal gear that would 'drop into' the external gear.

83 / (50+2) =~ 1.6 MOD

83mm = 3.268"

(50+2) / 3.268 =~ 16 DP

16 DP is the more likely.

Neil

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