Topic: BP Pulley/Sprocket Ratios

[Nkaratzas89]

Hey guys,

Over the winter Im building my Race Mower to speeds similar to a BP Im guessing.. I want to get a top speed around 50 MPH. My Race association has some different class names and specs so Im trying to get a sense of how fast I want it. Im going to run a Peerless 717 Transmission to a Live Axle, with 13" Rear Tires. Let me know what you think because Im not sure how to gear this set up to get 50 MPH in 4th gear (4 speed trans.) Im also running a 17hp Briggs OHV single with an EC Carb on it.

Any help would be great!

Nico

[George Herrin]

8 on motor 5 on trans 12 on trans to a 48 on axle will be pert near what ya want.

[stvn_VA]

EC has a very nice speed calculator for mowers under the technical tab on their website.    Input your RPMs, engine/tranny pulleys, sprockets & tire diameter and presto you have your speed!!   


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[Nkaratzas89]

8 on motor 5 on trans 12 on trans to a 48 on axle will be pert near what ya want.

Great, Thanks!

EC has a very nice speed calculator for mowers under the technical tab on their website.    Input your RPMs, engine/tranny pulleys, sprockets & tire diameter and presto you have your speed!!   


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Haha Thats awesome! Ill be sure to check it out

8 on motor 5 on trans 12 on trans to a 48 on axle will be pert near what ya want.

Would this ratio be with a governed or ungoverned engine?

[stvn_VA]

I have run that combo on both but if you want 50mph then you need to drop the governor and do some mods.  The 8/5 12/48 is just a good middle of the road starting point.  Its going to depend on the length of the track.  You said earlier you want to hit 50 mph similar to BP's.  First BP's are v-twins since you are a single you actually would have a CP.  50 MPH can be done fairly easily but not with a 12/48 for me running 25 tooth to 25 tooth on 16" tires on my single. That would require turning 8 grand and I don't do that.  You said you were going to run fourth gear so you might be fine.  Also it takes a little more real estate (longer track) or a banked track for a single cylinder compared to those built twins.  If you have a small to regular size flat track like most races I go to the set up that was recommend would be a very good starting point.  I would advise don't get caught up in a number you want for top speed.  Build what you can and what you can afford first and run it.  You can always improve later by changing sprockets.  Most of the huge big budget mowers never get to use all they got because the tracks are to small.  In my opinion torque is more important on small tracks than top speed.  Digging out of the turns for me is very important.

[Nkaratzas89]

I have run that combo on both but if you want 50mph then you need to drop the governor and do some mods.  The 8/5 12/48 is just a good middle of the road starting point.  Its going to depend on the length of the track.  You said earlier you want to hit 50 mph similar to BP's.  First BP's are v-twins since you are a single you actually would have a CP.  50 MPH can be done fairly easily but not with a 12/48 for me running 25 tooth to 25 tooth on 16" tires on my single. That would require turning 8 grand and I don't do that.  You said you were going to run fourth gear so you might be fine.  Also it takes a little more real estate (longer track) or a banked track for a single cylinder compared to those built twins.  If you have a small to regular size flat track like most races I go to the set up that was recommend would be a very good starting point.  I would advise don't get caught up in a number you want for top speed.  Build what you can and what you can afford first and run it.  You can always improve later by changing sprockets.  Most of the huge big budget mowers never get to use all they got because the tracks are to small.  In my opinion torque is more important on small tracks than top speed.  Digging out of the turns for me is very important.

Yeah That makes a lot of sense. I definetly want a lot of torque because my track is only 85 feet long. the 8/5  12/48 sounds like a very good ratio for the track and class ill be racing in. Thanks a ton for the help, Ill be sure to post how it preforms. Just wondering, how fast does your single go with this 8/5 12/48 set up?

[stvn_VA]

40ish


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[redline]

Yeah That makes a lot of sense. I definetly want a lot of torque because my track is only 85 feet long. the 8/5  12/48 sounds like a very good ratio for the track and class ill be racing in. Thanks a ton for the help, Ill be sure to post how it preforms. Just wondering, how fast does your single go with this 8/5 12/48 set up?

85' total length or length of straight? Big difference.