cyclo reducer with mc nylon components? 1

[Rinsuke]

This message/question is related to following topic :<<Spur or planetary gear box in light winch>> although I thought it warranted a thread on its own...

Again in the quest of building a light yet strong gearbox, I am requesting comments on the feasability of the following design:

Cyclo speed reducer 40:1
2 metric tons (4000 kg) on drum winch

Aluminium casing for reducer
steel shaft (SCM 435)
reducer itself would have aluminium ring gear (hardened)
mc nylon or (teflon?) pins and rollers
mc nylon cycloidal discs
slow speed shaft pins would be steel
steel bearings

TIA to all who wish to comment on design

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[Iskit4iam]

You can make the thing out of peanutbutter and PlayDoh if you make it big enough.

If you've gone through the calculations and the components offer you the service life you want you should know the answer. If you haven't there isn't enough information in the two threads for us to answer the question.

So, what do your calcs tell you? What components do similar designs use? My gut tells me the nylon gears aren't worth the weight savings over steel. Aluminum for the housing makes sense if cast.

 

[gearguru]

2 metric tons used to be 2000 kg (kgf in your case)...

 

[Rinsuke]

Iskit4iam,

ok, that is one piece of advice I won`t be using, unless you are talking about using peanut oil to run a hydraulic unit...

I don`t have any calcs . I am not an engineer although with appropriate reference material I can at least evaluate designs to a proposal level. The engineer then shreds the proposal or digs in further. This is something I did not state in the message .

Apart from Al housing, other makers and designers have not used any non-metallic material, or at least I am not aware of any production design (off the shelf) . Who knows maybe NASA has one similar gearbox on the Mars Rover, but that won`t do me any good this time around.

If you or anybody else, could suggest appropriate reading / reference materials on cycloids, I would be thankful. Please no recipe with peanut butter though/dough.

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[Iskit4iam]

Sorry about the peanutbutter suggestion. I was wearing my cynic hat.

 

[Rinsuke]

Iskit4iam,

no problem, I realize text based communication doesn`t always carry the right nuances. I saw your other posts on the threads and they looked quite helpful so , I certainly can`t hold this one against you. I have given the good ol` google a whirl but have not found any books on cycloids, although I may just have found what I am after... More later , probably in a fewdays...

stephan

 

[Spurs]

Rinsuke

Why are you interested specifically in cycloids? Do they have a percieved advantage over involute profiles in your application?

I do consulting work on the types of mechanisms that you are talking about. Maybe you need that kind of expertise here.

 

[Rinsuke]

Spurs,

the reason is mostly weight savings. and this helps too: &quot;many teeth are in contact at one time distributing the load so force-bearing gear teeth each have to bear less load. &quot;

quotes taken from internet site with information on products...

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[Spurs]

Rinsuke

The following exerpt is taken from this web site on cycloidal gears:

http://watchmaking.csparks.com/CycloidalGears/

The paragraph deals with the question of why use cycloidals at all.

&quot;This issue is somewhat controversial, but there seem to be three reasons: 1) The pinions are easier to make. As we shall see, the acting part of the pinion leaf is a flat radial surface. 2) The gear trains used in horology have multiple stages of wheels driving pinions where the pinions have very few teeth. Involute profiles for these pinions would be radically undercut, which would make them easy to break and difficult to manufacture. 3) It is traditional!&quot;

Points 1 and 2 relate to the concept that pinions with fewer numbers of teeth can be made without undercutting as compared to involute gearing. The supposition here is that there may have higher bending strengths because of this.

There is however a major disadvantage of using the cycloids as compared to involutes. Namely; in cycloidal gears, true conjugate action can only be achieved at one specific center distance. In involute gearing, congugate action can be achieved independent of center distance, meaning that the housings, assemblies, bearing etc. which all have stack up will not prevent conjugate action.

http://members.rogers.com/webgear/home.htm

 

[Rinsuke]

Spurs, seems we are almost real time here. I am in Japan and it is 12:31 noon. Ok , before we go any further , I want to avoid any confusion: this is what I am talking about :&quot; Differential epicyclic gearing&quot; and you can see an example of it here:
<

http://www.micromech.co.uk/dir_products/prod_range_sumitomo_gearboxes.asp>

My apologies if I mislead you with the wrong terms ...

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[Iskit4iam]

Rinsuke,

Are you refering to sumitomo cyclodrives? There are no traditional gears in this type of speed reducer.

http://cyclo.shi.co.jp/eng/product/gmoter/saikuro6000/sa60020.html

This link has an animation that explains the components and their geometry. I've used them but never paid any attention to the internal component design parameters. I'd be surprised if you make internal components out of plastic.

 

[Rinsuke]

Iskit,
Yes this is the one I am talking about.

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[Iskit4iam]

Well Rinsuke I think everyone else was talking about spur gears with cycloid or involute tooth shapes. I know I was. I don't think there are any published standards for the design of cyclodrives. To the best of my knowledge only sumitomo makes them but I woulen't bet on it. I think you would benefit from trying to buy the &quot;gear&quot; set from them. &quot;gear&quot; because they are not gears. Good Luck

 

[Rinsuke]

Iskit,

Sumitomo is not the only maker, although they are, I will concede, few and far between. I have found Turkish makers, Chinese makers and a Korean maker but they have a fraction of the offering that Sumitomo has. There is also another Japanese maker by the name of Nippon Denso/ Shimpo and their US affiliate, Nidec America which seems to offer a large selection. Problem is, none meets our specs, size and cost wise. I have since found a small design partnership in Seattle that has a few prototypes built but my emails went unanswered after over a week now.

Sumitomo does labelled the outer ring with the pins and rollers the &quot;ring gear&quot; but you are right to say that otherwise they are not called gears. The input shafts and attached &quot;gear&quot; is called cycloidal disc. It does have teeth though, so why not call it a gear as well?

I am tempted to start work on a modified design, but will first have to let the idea(s) simmer for a while longer...

Thank you for your help and kind response so far. If anyone wish to comment on the Sumitomo cyclo drive and their experience with it or if you have any reference material on the design of such drive , I would be most thankful.

>>> The cyclo story<<<
Lorenz Braren invented the Cyclo gearbox and founded Cyclo
Getriebebau GmbH in Munich, Germany, in 1931. He rewrote
engineering history when he was granted a patent for his invention,
which introduced a totally new concept in speed reduction.

The Cyclo is a speed reducer without a high speed pinion or gear
teeth; it does not operate in shear but in compression. This means
that users of Cyclo speed reducers enjoy a valuable benefit - no
catastrophic failure. Following World War II Lorenz Braren continued
to perfect the Cyclo gearbox until he died in 1953, at the age of 67.

In 1974 Sumitomo Heavy Industries, one of the largest manufacturers
of machinery in Japan, acquired an interest in Cyclo Getriebebau
GmbH. In 1994 the Japanese bought the German company outright
and in 1996 the company began to gradually develop the market place
in Europe.

<<<

 

[tonim]

Rinsuke,

I sympathise with your problem. Material is not easy to find on the web. Try these guys for gear design software. It might help you on your way.

http://www.amtecinc.co.jp/gallery.html

 

[ischgl99]

Darali also makes cyclo gearboxes, their website has some info that may be of help.

http://www.darali.com

Mike Bensema

http://www.dutchmenservices.com

 

[patprimmer]

I think you will need to do a lot of research to determine point loads and operating temperatures. You might then be better armed to make rather radical material selection choices.

If it seems feasible to go with plastics, I have a LOT of data on friction, bearing and gear design with some fairly special high performance plastics.

This is not realy a gear, but more a bearing by it's apearance.

The plastic materials that might be considered if the loads and temps are not to high are:-

Nylon 4.6 (only original source is DSM Engineering Plastics)

Graphite and molybdenum disulphide filled nylon 6.6

Approx 80% bronze filled or bronze and PTFE filled nylon

Carbon fibre filled nylon.

Various filled PETs

Various filled acetals

Maybe some exotics like PEK, PEEK, Polyether Imide, but they get very expensive.

Sources of custom compounds could be LNP, DSM Engineering Plastics, RTP, or Duromer Products.

I do have a comercial relationship to Duromer, so I should not comment further than purely technical comments re their products on this forum.

My e-mail is pprimmer@acay.com.au

Regards
pat

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