GEAR MATERIAL

kriskros

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Feb 3, 2009
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i am looking for a plastic material that would be suitable to MACHGINE the Cyclone planetary gears..factory specs ,torque is 80kg/cm... must be VERY durable,low friction,and quiet..any suggestions would be much appreciated e.g. would delrin be a suitable material?? what would be the best??:mrgreen:
 
Time for some research. I see 223 different blends of Nylon. Compare specs to white delrin. I hear they put a pigment in it to make it black so it's not as strong.

http://www.matweb.com/

type in "nylon" in the search bar.

This MatWeb should be a "favorite" in every builders tool bar. Some 93,000 different types of materials.
 
Hi CogHog

Yes, nylons are one of the big families. You can get nylon without pigment. Blond colored naturally. Lots of modifiers are added so I would stay to one of the gear grades. Delrins I found to be very brittle when machined. Generally softer and very sensitive to notch failures. I don't know of them being good for high power either. Lots of history on them.
 
I have machined Delrin and 6/6 nylon, the delrin is more silppery because of the teflon content, The 6/6 nylon is more gummy. Take a look at Mcmastercarr, some good information on some composite nylons and delrin. Both used for gears.

Very-Wear-Resistant Kevlar-Filled Nylon
Self-Lubricating MDS-Filled Nylon
Wear- and Moisture-Resistant Nylon 6/12
http://www.mcmaster.com/#standard-nylon-sheets/=l3cj6h

Wear- and Water-Resistant Delrin
http://www.mcmaster.com/#acetal-homopolymer-sheets/=l3cl3c
 
i have had nylon gears in both bafang and puma motors...didnt las 300 miles. unless yo add one steel gear,but the steel gear nylon cimbo is noisy.. the cyclone has a much higher torque than either of these motors :mrgreen:
 
TMaster said:
I have machined Delrin and 6/6 nylon, the delrin is more silppery because of the teflon content,

Delrin is an acetal, which is slippery kind of resin considered to be self-lubricating. But it contains no Teflon or any other kind of PTFE.
 
Chalo said:
TMaster said:
I have machined Delrin and 6/6 nylon, the delrin is more silppery because of the teflon content,

Delrin is an acetal, which is slippery kind of resin considered to be self-lubricating. But it contains no Teflon or any other kind of PTFE.


That's correct. Unless it's delrin AF, which amazingly does contain bits of PTFE to act as a friction modifier at the cost of some structural properties.

http://www.plasticsintl.com/datasheets/1884849888Delrin_100AF.pdf


If I was going to go through the trouble of actually making a gear, I would make it out of brass or steel so it has a shot at lasting. IMHO, the reason for the plastic gears is more so they can tool up for a cheap but accurate injection molding process to make them over it being more quiet. Not that it isn't more quiet, just that other techniques in gear tooth design can also help metal gears to become quiet, but the post machining on the metal gears is always going to be more expensive than a gear that can be used just as cast in an injection mold.

That said, if you want plastic gears that you're going to machine, the answer likely isn't any single compound/polymer or whatever, it's likely some of the fiber-filled materials that have good resistance to creep/fatigue related failures (like teeth getting mushed over to the side a few degrees until they don't engage well and strip after time).
 
I agree on using metal if the torque is high. Most of the folks here seem to be looking for more power and speed and would spell trouble for most of the resins at some point from over stress.

In light torque the plastic gear types (lubricated) of both the acetal and nylons will out last the metal counterparts in many applications. Pinning / keying them to shafts are another nightmare however. In my experience the nylons are much more forgiving with machined details/ finish issues and longer lasting when up against hard steel. Good option may be to use a glass filled type if wear is less of a issue than strength.
 
Fiber filled (glass,kevlar or carbon short strand fibers) nylon or acetals/delrin offer a VERY large increase in strength over there unfilled versions. I bet macs new grey gears use fiber reinforced plastic. PEEK plastics and the fiber filled versions are the ultimate plastics and can be very expensive but are approaching soft metals for strength. Most of the geared hubs i have seen have very very sloppy tolerances and the gears only just mesh and load up only the tips of the very weak teeth. You need high modulus materials(stiffness) to maintain gear tooth form and correct tooth contact patch so fiber reinforced materials are superior. Plastics modulus(stiffness) plummet with increasing temperature! Again PEEK plastics are far superior.
To machine the gears mill a long section of gear and then just part them off.
Maybe you could look at using std. gears and either turn down the width of a spare gear set and make 150% or 2 gears wide and a small gearbox widening spacer?
Either way try and open up the motor for cooling they have very bad heat dissipation by design.
I'm a machinist by trade and have been involved with gears sets up to 10m in diameter.
Zappy
 
with increasing temperature! Again PEEK plastics are far superior

Good post. Agree. Peek would be a good choice in hot gearbox. I was party to sampling some for a Injection Molding job some years back. I recall it had a few percent of MoS2 "Moly", PTFE with some glass in the resin. I remember the parts having a reasonably good surface finish and sounding like a piece of china when tapping on them lightly. Parts were very accurate in molding dimensions and much harder than similar grades of nylon or delrin. It was very expensive I recall.
 
Miles said:
kriskros said:
i am looking for a plastic material that would be suitable to MACHGINE the Cyclone planetary gears..
Why go to all the trouble of custom machining a set of planet gears when you can buy stock gears?


Yes, that is a very good point Miles. I would imagine no less than $500 invested to make a set of plastic gears from scratch, and they are quite likely to be worse than the factory gears.
 
$500 invested to make a set of plastic gears from scratch, and they are quite likely to be worse

Yes, "a good education is expensive, no matter how you get it". I think it is great that someone is trying to improve things. I wish him well.

Old saying, "if it ain't broke...", new saying, "if it is not perfect, improve it". :)

Ran into a rep I worked with a few days back and mentioned the noise metal gears vs plastic gear grades. He pointed me to new resins in the zytel line. Impressive improvements the last few decades. Some have glass transition temperatures that rival PEEK. I guess with all the hot under hood applications, there was sufficient market to invest in the r&d. Some great data. http://plastics.dupont.com/plastics/pdflit/americas/markets/Gear_Brochure_10_2007.pdf
 
I've got a cute q100 (ananda) geared hub motor and the gears are starting to fail. Searching these forums and the rest of the net it appears that replacement gears aren't available and many people have stripped gears on these motors.

I was considering trying to get a replacement set of gears made from a place such as http://gearsmade.com/. Ideally I'd like something significantly stronger than stock. Perhaps if I can test a sample set or two and get good results I could do a bigger order (100 units?) to get the price down and offer them to others... My guess is the gear sets would need to be made for $40 a set or less so that I could offer them at roughly $60 or less as the motors typically sell for only $70-$80 from Chinease resellers (though more stateside after shipping).

So back to the thread topic, what's the best choices regarding materials and gear (re)design? Is this even possible or would it likely prove too ridiculously expensive at small volumes?
 
fropm considerable research,gettiung in fo from manufacturers and gear makers,the best material for plastic gears is torlon...available in rod for maching or powder for moulding..torlon will take high heat..500 degrees.. and is very hard and durable.. there is a lot of torque on planetary gears :mrgreen:
 
Good rule of thumb for a very basic injection mold to make a simple part like this is that you would start to consider it with minimums of 2000-2500 parts. For a production tool, 5000-10000 parts. Agree, one of the gear grade nylons would be best. Drake makes "torlon", Dupont makes "zytel", but I would see what you can find in rounds. Machining them in long sections from rounds is most likely the best approach at your volumes. 50% glass makes for very strong stuff but even with 30% glass, the nylons are still plenty strong for most applications. You can carefully weigh , burn off and re weigh the remaining glass of a destroyed gear to zero in on what is stock content is for bench mark.
 
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