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Roller chain and sprocket rpm?

Ray Behner

Diamond
Joined
Mar 27, 2009
Location
Brunswick Oh USA
Would it be an excessive rpm to have a PTO shaft at 3000 rpm reduced by #50 chain and sprockets to 540 rpm. I know the reduction is possible, but is this to much to ask as far as rpm input?
 
Ray,
According to a book I have (Marks' Standard Handbook) for #50 chain the max RPM is 2200 as long as your smallest sprocket has at least 24 teeth. If you go to #40 chain with a 24 tooth min. sprocket 3000rpm is the max.
 
Clearly doable. For a Harley to make 90 MPH with a 25" dia rear tire and 3:1 reduction to rear wheel, the output sprocket at tranny had to turn 3630.

I see they also went to belt drive though.......:)

John Oder
 
I'm not going to do the engineering for you, but look at a mid 1960's Old's Toronado
It has the Rocket V-8 yet, a new 385-horsepower version of a 425-cubic-inch engine its output turning a sprocket and chain drive to the front wheel drive transmission...

Of course, the Toronado's most unusual aspect was that driveline. The standard and only available transmission was a special split version of the famed Hydra-Matic, with the torque converter directly behind the engine and the gearbox mounted remotely under the left-side cylinder bank. Connecting them was a two-inch multiple-link chain, and differential torque was split evenly between the half shafts. This arrangement produced surprisingly balanced weight distribution for a big front-driver -- 54/46 percent front/rear -- and contributed greatly to the car's over-the-road prowess.


http://auto.howstuffworks.com/1966-1970-oldsmobile-toronado.htm
 
I think it would depend on the sprocket size. At 3000rpm the chain is moving much faster (more centrifugal force) on a 96 tooth sprocket than a 24 tooth sprocket. (Since you are reducing speed, I assume you are using a small sprocket at 3000rpm.)

Just my personal opinion (take it for what it's worth) I would never run a #50 chain at 3000rpm no matter what size sprocket. I would use a gear reducer for that application.

Aaron
 
Before car engine manufacturers started to use the sprocket toothed rubber belts to drive the cam, there was always a chain to do that job, and it very rarely broke to wreck all the valves, like the rubber ones do. I don't remember ever reading that you had to keep the engine crankshaft speed down to any value to prevent the chain from breaking.
Chain feet per minute I can understand whilst transmitting HP. And Max HP to be transmitted I could understand.

For instance, consider a 1:1 chain drive with both shaft turning at 1000 RPM.

If the sprockets are 6" diam the chain is moving at 1570 Ft/min
If the sprockets are 4" diam the chain is moving at 1047 Ft/min
Depending on the chain type, could one sprocket diam be valid and the other not valid ?.
If you got yourself a 12" sprocket and wrapped a chain of exactly the correct number of links round it and joined the ends together, I think you could spin it pretty damn fast without it flying apart by centrifugal force. Chain speed would be 3141 Ft/min at 1000 RPM
But it is not transmitting any power.

Davycrocket
 
Motorcycles run 24T #50 size sprockets way over 3000 rpm, as high as 10,000 rpm and more for short periods.

Is your question about chain mfgrs. recommendations, or about chain life, or catastrophic failure? Very high speeds make the chain hot, requiring an oil bath for long life, but 3000 is not what I'd call very high speed. An O-ring chain would help if you are worried about longevity.

Reducing 3000 to 540 with a 24 pitch primary sprocket would require a 139T secondary. If both sprockets are close together the small sprocket would not have much 'wrap' or chain engagement which could reduce the life of both the chain and the sprocket.

How much load is on this?
 
go with a double reduction with the first reduction using the smallest drive sprocket you can get that has an odd number of teeth.

this will keep the sprocket sizes down to manageable sizes and keep tooth contact within reason.

do it up in a welded steel case and add some oil, then off you go.

i have seen 350 chevy engines with dual roller cams run well over 300k miles and the chains still look pretty good.

so maybe you use a chevy cam and crank gear as the first reduction, and follow that with the needed reduction in single row #50 for the final drive?

the chevy cam drive is not running in a pool of oil, it is just what leaks out past the cam bushing and the front main brg, and is thrown around inside the case.

also if you try to do it in a single reduction, you ought to provide for some sort of auto/spring loaded tensioner, if for no other reason but to keep the chain whip under control. there will likely be issues if you don't, so plan for inclusion of some sort of tensioner before hand when it is easier to incorporate rather than later.

another viable option would be either a cog belt (probably a better solution) or a microgroove/serpentine type belt (not as good as a cog drive but better than a chaindrive in my opinion,, neither would require lube but both would benefit or require a tensioner.

fwiw

bob g
 
Thanks for all the input. This is for a 5' snowblower, so it'll take some abuse and power. The "H" series timing belts are cheap enough, but when it comes to the pulleys....Yeow! Yes, I figured on making a sealed box for the reduction, regardless of drive type. If roller chain, it'd be sealed for oil. They makin' is easy. The figgerin' out is the tough part. I've got a Hustler 4WD mower with a 30hp diesel and want to run an old PTO driven blower.
Thanks guys!
 
Ray

Tsubaki rate their RS80 chain up to 3000rpm on the small sprocket, provided it's 18T (less if smaller)
The chart makes it impossible to see the top limit on the RS50 but of course it's well higher, so even though these are premium chains, you should have no problem whatsoever at the much lower speed you're proposing.

I recently designed a multistage chain reduction, and we tested it to destruction by hoisting a 3 tonne load (which was already a gross overload in terms of the ratings of at least three of the chains) and then allowing it to freefall, driving the train from the output end. The speed was self limiting, but ultimately the input chain disintegrated at 22,000 rpm. This was 3/8" chain on a 13T sprocket - and it had a joining link! (ie not endless).
The gearbox was undamaged. We called that a pass.
 
Thanks Tim,
I get their catalog, mostly for hyd. parts, but I'll take a look.
Troup,
Very interesting test! I've dealt with US Tsubaki in Sandusky, Ohio for that little dozer I made. Kinda know the guy I dealt with. May give him a call.
 








 
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