Increasing chain drive efficiency 1

[ccaissie]

I am building a chain drive version of a geared "two man hand powered rice huller" for the Maine Rice Growing Project. I'm copying a Japanese made impact type huller that works well.

Initially the idea of using sprockets and chain seemed feasible to increase the speed from a manual input of 75rpm raised to 2500rpm in two stages. When the forces to operate it seemed high, I wondered if there were inherent issues with using chain drive to increase speed rather than reduction which is more common...I designed conveyors for sawmill operations...

Without the chain, all parts are free to rotate, but the chain is a major load issue. On a whim, I just rinsed the grease out of the chain with mineral spirits and the load was much lighter, so I am pursuing a friction reducing strategy. I recently accessed an old thread here thread406-63684 which began to address this issue, and I'd like to take it further.

1. What chain lube would be a probable replacement for the Chinese grease? For the chain, I'm thinking a real good rinse of the old stuff, and some high tech teflon or ceramic based oil...think tour de France.
2. Are cheap Chinese chains that much worse for friction than a Tsubaki or other better grade chains?
3. Since loads are relatively low, are there strategies for pushing/flushing out the Chinese grease in the pillow block ball bearings and introducing a lighter synthetic grease, or introducing a high tech oil, or running them almost dry with a high tech oil?

Thanks for any ideas/inquiries.

Colin

 

[MikeHalloran]

Better chain.
Better bearings.
Low viscosity oil, fed steadily.
Don't expect miracles; you may still need to add more cranks and more people.

Speed increasers in general are very difficult to get right. My friend Wayne spent WW2 rebuilding supercharger drives, which used precision bearings and precision gears. The gears had to be selective fit (to share the load in planetary sets), and the drives still grenaded on a fairly regular basis.




Mike Halloran
Pembroke Pines, FL, USA

 

[Tmoose]

In many circumstances O-ring chain would be considered "better."
I'm thinking you would not like the o-ring drag, nor the difficulty experimenting with different lubrication.

I wonder how a toothed belt would compare, and the effects of sprocket size.

 

[MikeHalloran]

Speaking of belts, Poly-V belts have been used in some modern supercharger drives. You might take a look at them.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

- If budget permits, enclose the chain drive in a sealed housing and use splash oil lubrication. Using oil lubrication and keeping the sliding interfaces of the chain (plates, rollers, pins, sprocket teeth) free from abrasive debris will improve both efficiency and service life.

- Optimize your two drive stages to use the smallest standard chain and sprocket sizes available, keep the shaft/sprocket center spacing to a minimum, and tension the chains correctly. This will minimize friction losses. Looking at the photo provided of your existing chain drive, it appears you might be able to use a smaller size standard roller chain and sprockets. Your output sprocket is rotating at a fairly high 2500rpm, so to minimize the effect of chain speed variations it should have at least 19 teeth. The number of teeth for the driven sprocket of the input stage should be selected based on the required corrected power capability for a single row chain. If you prefer to use common sprockets for both stages, select one with the minimum number of teeth that meets both requirements.

- Make sure the sprockets and drive shafts are accurately aligned, and the chains are properly tensioned. Excessive contact sliding between misaligned chain plates and sprocket tooth side faces as they engage/disengage will increase friction losses.

- It might also be helpful to reduce the inertia of the rotating components by cutting some lightening holes in those large diameter steel plate sprockets.

Here is a design guide that should be helpful to optimize your roller chain drive:

http://www.iwis.de/uploads/tx_sbdownloader/KettenHandbuch_E.pdf

 

[MintJulep]

2500/75 = 33.3

Whatever torque this thing needs at the 2500 rpm shaft gets multiplied by 33.3.

Should not exactly be surprising that "the forces to operate it seemed high."

 

[Compositepro]

Thin flat belts on crowned pulleys have low friction and are low cost. Where I see them used most is on lathe tool post grinders where the belt is used for increasing rpm.

 

[MikeHalloran]

Is there some reason you can't just buy the Japanese version?

How is yours different, other than the drive?

Do you have any idea how much power the operation actually requires?

Even in the Maine backwoods, you can probably find enough electrical power to run a 1/4 HP electric motor, which will out-work two athletes all day long.




Mike Halloran
Pembroke Pines, FL, USA