Steve - The chain number indicates pitch. ie #40=0.400 #50=.500 ect. The larger chain is stronger for sure but it will be harder to get a small diameter sprocket the larger you go. I'd suggest looking for the sprocket gearing you want first then the chain.
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Archive through July 15, 2011
- Thread starter kmcconaughey
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mgonitzke
Well-known member
Steve-
What is the maximum HP output of that engine, and what RPM does it occur at?
What is the maximum HP output of that engine, and what RPM does it occur at?
mgonitzke
Well-known member
A couple of quick calculations makes me think you might be able to get away with #50 at 60 hp. If you go any larger I suspect you are going to have a space issue in the case, due to the size of the sprocket you must fit on the hydro trans output.
On the other hand, you might be able to get away with smaller chain...there's no way you're going to put 60 hp to the ground just by driving this thing around.
On the other hand, you might be able to get away with smaller chain...there's no way you're going to put 60 hp to the ground just by driving this thing around.
mgonitzke
Well-known member
Steve-
Hopefully Marlin will chime in here on the strength of the hydro unit, but I suspect the input shaft would fail somewhere in the vicinity of 60 hp. I'm not sure the internals would be able to handle that, either. I can't remember what the input shaft looks like in there, it's been too long since I've had one apart. You may also have cooling issues unless you run it only for short periods- 15% power loss creates a lot more heat from 60 hp than it does from 16 or so.
A couple of other thoughts: What are those U-joints rated for? It looks like you have a 3/4" shaft in your driveshaft; if those U-joints are similar to the high-torque ones on McMaster-Carr, they will not handle the torque your engine produces at 45 hp, and they're only rated at 1000 rpm. At the very least you need to build a very beefy driveshaft guard so if one of those U-joints explodes or the shaft breaks it will not kill anyone.
I think 60hp would also break the axles and/or carrier, probably long before anything else breaks, with the possible exception of the U-joints.
Hopefully Marlin will chime in here on the strength of the hydro unit, but I suspect the input shaft would fail somewhere in the vicinity of 60 hp. I'm not sure the internals would be able to handle that, either. I can't remember what the input shaft looks like in there, it's been too long since I've had one apart. You may also have cooling issues unless you run it only for short periods- 15% power loss creates a lot more heat from 60 hp than it does from 16 or so.
A couple of other thoughts: What are those U-joints rated for? It looks like you have a 3/4" shaft in your driveshaft; if those U-joints are similar to the high-torque ones on McMaster-Carr, they will not handle the torque your engine produces at 45 hp, and they're only rated at 1000 rpm. At the very least you need to build a very beefy driveshaft guard so if one of those U-joints explodes or the shaft breaks it will not kill anyone.
I think 60hp would also break the axles and/or carrier, probably long before anything else breaks, with the possible exception of the U-joints.
The military/government HP rating of the 4A084 engine is 20 HP @3600 RPM, but since the smaller 4A032 is rated at 6 HP and supposedly dyno's at 18-20 HP, I would think the 84 would probably be in the 40-60 HP range, but that is just a guess.
Matt,
I know I'm not working with the best components for the job, but this project started life as just an overpowered parade tractor. It only morphed into an actual dragster when I found out that they hold lawn tractor drags locally twice a year. I couldn't pass that up.
My plan currently is to try to be careful with my launch. I'm thinking rev it up to about 2000rpm, go full throw on the hydro, then pin the throttle. Let the engine pull it up to speed, not force the hydro to deal with full power from a standstill. If I replace th 6:1 gear reduction with a 1:1 chain drive it should be good for 60mph @ 3600rpm. Still trying to figure out what to do at that speed if the engine quits... hydro lockup and all that.
I know I'm not working with the best components for the job, but this project started life as just an overpowered parade tractor. It only morphed into an actual dragster when I found out that they hold lawn tractor drags locally twice a year. I couldn't pass that up.
My plan currently is to try to be careful with my launch. I'm thinking rev it up to about 2000rpm, go full throw on the hydro, then pin the throttle. Let the engine pull it up to speed, not force the hydro to deal with full power from a standstill. If I replace th 6:1 gear reduction with a 1:1 chain drive it should be good for 60mph @ 3600rpm. Still trying to figure out what to do at that speed if the engine quits... hydro lockup and all that.
