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Snowblower speed

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Well, I finally got the Agco Allis 918H in working shape.  This free to me tractor has now cost me about $350 to get running, and I picked up a blower for it also.  It runs fine and the hydro is solid, nice tires and seat, all in all a decent tractor.  Anyway, I put a new set of chains on it today (pics in show and tell) and set it beside my Allis T816 which I have used for years for snow removal.  With them both running and blowers engaged, the Agco blower runs alot faster than the T816 does.  As far as I know they both have the right pulleys and belts on them.  Was the T816, which is the same as the Simplicity 6216, made to run slower?  I have read about bigger and smaller pulleys on the blower but I think they are both original.  Anyone have any info on this?



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I'm thinking they should be about the same speed since they are both RBTs of roughly the same vintage.

The OEM setup for the RBT "Sovereign" type tractors is a 7" diameter driven pulley on the snowblower.  It's very common to change them out to increase the speed.  I run a 6 1/2" pulley for my setup.  6" seems to be common as well.  As you go smaller, the long belt drive belt should also be a little shorter - 3/4" for a 6 1/2" pulley and 1 1/2" for a 6" pulley.  On the 7100 series tractors, the OEM belt adjustment definitely covers the 6 1/2" pulley and probably the 6" as well. 

Another issue is engine speed; in my experience, many of the tractors aren't governed at the "design" speed of 3600 rpm, but more like 3400 or 3500.  This also makes a difference.  

I'm don't know how the T816 is setup; all my experience is with large frame tractors. Years ago measured "belt wrap" lengths for various pulleys and did some calculations (belt wrap is a more accurate calculation than just pulley diameter since it takes into account how exactly where the belt rides in the pulley V grove).  Based on OEM pulley, I found that the FDT pulley setup turns the blower 0.866 rpm per engine rpm and the 7100 series mid PTO setup turns the blower 0.752 rpm per engine rpm (13% slower).  I've never had a mechanical front PTO (standard for 7000 series) to measure, but for a front electric PTO (Allis 300/400 & Allis build Homelite tractors), it turns the blower 0..786 rpm per engine rpm (9% slower).

Hopefully this helps you some.

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