Does engine HP affect driving power

[Taters525]

My father in law let's me use his 25hp HST tractor quite often. Some of it's use is maintaining the road we live on. It really struggles going up any kind of hill especially with a load of gravel. I know the engine hp doesn't affect lift capacity because it's really based on what the hydraulic pump can do. But what about a HST transmission. Really not that familiar with how those work. Are they hydraulically driven. Basically I'm asking about it I buy a tractor and get a 40hp or so engine will that alleviate the issue of not being able to pull hills very well

 

[ericm979]

With an HST you want to use only a little pedal when you're going up a steep hill. The farther down you push the pedal, the higher (numerically lower) the gear ratio, which is the opposite of what you want. If your tractor has linked throttle and HST you may need to use the hand throttle to raise the RPMs. If it's too steep you need to stop and put the tractor in a lower range.

Gravel is really heavy. A bucket full weighs a lot.

A tractor with more power will also be larger and heavier and have a larger bucket that holds more gravel. Depending on the specifics it may or may not be faster up hills. Manufacturers tend to use a given "frame size" for a range of engine powers. So you can look for the more powerful model in a given frame. For example the Kubota L3301 and 3901 are pretty much the same except for engine HP. Sometimes the more powerful model has a turbo.

 

[Avenger]

HST stands for HydroStatic Transmission. It is hydraulic power that turns the wheels. They are, in a way, easier to drive, but less "powerful" than a 'gear' tractor. That said, make sure you are keeping your RPM's up. Gravel is heavy, and moving it uphill is hard on these little tractors.

The larger the tractor, the heavier it is. Filled tires also adds weight. Your gear selection is another factor. What gear are you in? The more you mash that pedal down, the more the pump has to work, the engine bogs down. Try a lower gear or less pedal pressure.

My tractor is a gear tractor. I have loaded tires. When I'm in road gear, Range 4, gear 4, with the gas pedal mashed, it will bog down climbing hills. I need to shift down and that will cause me to slow down. But in Range 1, gear 1, that tractor could go straight up, if the tires would grip.

Just need to find that sweet spot. Your Father-in-law's tractor will go up that road, just gotta get the right combination of RPM and gears, pedal pressure.

 

[sea2summit]

Basically I'm asking about it I buy a tractor and get a 40hp or so engine will that alleviate the issue of not being able to pull hills very well

I can definitively say, maybe.

All else being equal (HST transmission, filled tires, make, etc) if the 25 HP bogs down when carrying 80% of a bucket the 40 HP will probably bog down with 80% of a bucket. Now 80% of a 25 HP bucket may only be 20-50% of the 40 HP bucket so you may bog down at 80% but you're getting 50-80% more work out of it so technically you're doing more faster...if that makes any sense.

 

[Farmer495]

Power to weight ratio is key.

Pretty sure any hill I can go up in high gear wide open throttle on a 70 HP gear drive tractor empty, I can go up with the bucket full. Function of size of bucket too.

 

[jeff9366]

Did your FIL show you now to release tractor's PARKING BRAKE?

 

[crazyal]

Long story short is yes, HP, makes a difference in everything a tractor does. Think of going up a hill on a bicycle. The higher the gear selected the harder it is to pedal. If you are a weak little boy you are going to struggle more than a guy who has stronger muscles. The way to get around it is to use a lower gear which means going slower.

There's nothing magical about HST. It's a pump that pushes oil that turns a (hydraulic) motor connected to the wheels. The pump speed is connected to the pedal. Push down and the pump tries to pump oil faster. That in turn spins the hydraulic motor faster. If the engine doesn't have the power needed it'll bog down (could even stall).

There's an exception to this but it's less likely to be an issue with a small HP CUT. Go back to the bike. If you are super strong and really push hard on the pedals and the hill is super steep you could break the chain. On a tractor they put in a safety valve. It's job is to prevent things from breaking. If going up a hill and the engine is running fine but the speed has dropped way down it's most likely that the safety valve is preventing the pressure from getting too high and breaking something.

My personal opinion is 25hp is right at the lower end of what I would want in anything but the smallest sized tractor. It'll need all of that HP to do most tasks. If you've used one and felt that it can do the job but you have to go really slow then I would suggest going up to at least 35hp. Rarely do people regret buying too much HP. But as you go up in HP you often go up in tractor size. A larger tractor will need a little more HP just to stay even with the smaller lighter tractor.

 

[LouNY]

Power to weight ratio is key.

Pretty sure any hill I can go up in high gear wide open throttle on a 70 HP gear drive tractor empty, I can go up with the bucket full. Function of size of bucket too.

I road my tractor and several other frequently.
From my place to the farm is three miles with several hills,
with just the bare tractor and front end loader (80 engine Hp) I can pull all the hills in high gear.
Drop my bucket off and install the grapple and carry the bucket at least one hill will require a down shift.
Hook up the brush hog, a trailer, or snow blower and three hills will require down shifting.
One of the places that we chopped corn on has a couple of hill that will make a 7130 IH Magnum drop a couple of gears empty by it's self,
when I have the pull type forage harvester and self unloading wagon with a load behind me two of the hill will make me downshfit from 18th gear down to 10th.

Depending on the bucket size many tractors couldn't pull steep hills with a full bucket of gravel in high gear.

 

[ptsg]

I road my tractor and several other frequently.
From my place to the farm is three miles with several hills,
with just the bare tractor and front end loader (80 engine Hp) I can pull all the hills in high gear.
Drop my bucket off and install the grapple and carry the bucket at least one hill will require a down shift.
Hook up the brush hog, a trailer, or snow blower and three hills will require down shifting.
One of the places that we chopped corn on has a couple of hill that will make a 7130 IH Magnum drop a couple of gears empty by it's self,
when I have the pull type forage harvester and self unloading wagon with a load behind me two of the hill will make me downshfit from 18th gear down to 10th.

Depending on the bucket size many tractors couldn't pull steep hills with a full bucket of gravel in high gear.

But then again, on a geared tractor, you can simply downshift on the move and keep going at a slightly slower pace.

With HST tractors, and there are a lot of threads about this, some with barely move in High range, others will start climbing the hill and then fall on its face, needing a complete stop to change to medium range to keep going. This is simply a no no if driving on the road.

 

[Industrial Toys]

Think of a hydro as a variable displacement pump. The more you step on the pedal, the larger the volume of liquid it pumps BUT the less mechanical/fluid advantage delivered.