Well now I've gone and done it...

[Gravy]

If the engine rpm is the same, you will have the same speed as before.

If you want more speed, get larger diameter tires.

What you have is extra HP above what is required to power all pumps at maximum.

I don't think it's any faster at top speed, but it maintains any given speed with much less effort. The original engine did not have nearly enough HP to power all of the pumps simultaneously at maximum load. I think that over the years I have read that the tram pump needs at least 12hp at maximum rated speed & pressure, the main PTO pump needs 8hp, and the auxiliary PTO needs about 3hp. That adds up to about 23hp. No problem for a 25hp engine, right?


Well, not so much. The 25hp number is a maximum gross hp rating - or to put it another way, wishful thinking. The recommended continuous net hp for the Robin EH72D (and probably most any other 750cc class small engine) is around 16-18hp, which falls pretty badly short of the real power requirements. It's close enough that we can slow down and still get the job done, but it takes a good bit of skill and patience.

So far, the new engine allows me to be a good bit less impatient.

 

[Gravy]

The machines that are designed for slopes should have enough power to do the job at the advertised angle.

As your machine get work/older, it will not meet the specs.

I think some of you are asking the machine to do more than it is designed.

This is just my opinion, but why would you not designed for less HP for the pumps requirement, plus some extra.

Have you ever heard of 110 percent.

Maybe PT is not telling the full story. Like will my 425 climb a 30 degree hill with mower running full out and not stall?

I think this falls into the category of "6HP" air compressors that run on a 120VAC 15amp circuit and produce the same pressure and CFM as an old style 2hp compressor. In other words, the marketing department overruled the engineering department.

 

[KentT]

The pump would bypass based on pressure, not volume, so it has no real relationship to speed in normal use. It would bypass (if at all) in the irresistible force against an immovable object scenario, such as pushing a loader bucket into a pile of dirt or stone... rather than stalling the engine, you'd force the pump to bypass, or with my luck, you'd break something unanticipated -- such as a lift arm mounting point. :laughing:

 

[KentT]

I don't think it's any faster at top speed, but it maintains any given speed with much less effort. The original engine did not have nearly enough HP to power all of the pumps simultaneously at maximum load.

So far, the new engine allows me to be a good bit less impatient.

Exactly -- you cannot provide both maximum power (torque, based on pressure) and speed (based on flow) with the stock engines...

I would caution though, as Moss infers, that you might find other components of the PT's design that aren't designed to handle that much power. I'd never have imagined bending the QA plate, which I've now done twice, after upgrading the wheel motors. In both cases I was using reverse treadle to pull the minihoe backwards...

I've damaged my PT more with the minihoe than any other attachment because the 4ft boom magnifies stress, IMO...

 

[Gravy]

Makes you wonder if you had more HP available, and you did not back off the pedal as you would with the lower HP engine, would the pump be able to handle the added HP or blow up? Or bypass, I mean. Since none of us have apparently ever hit the bypass on the tram pump, lets add some more HP and push them till they bypass, then back off the HP. Right? :laughing:

I'm going with the theory that the pump manufacturers specifications are based on real continuous industrial horsepower, as opposed to the fantasy momentary peak horsepower advertised by small engine manufacturers. I'm not worried about the pumps. As long as the reliefs are working, they absorb as much power as they need and nothing more. The only way to blow one up should be to overspeed or overpressurize it.

 

[Gravy]

The pump would bypass based on pressure, not volume, so it has no real relationship to speed in normal use. It would bypass (if at all) in the irresistible force against an immovable object scenario, such as pushing a loader bucket into a pile of dirt or stone... rather than stalling the engine, you'd force the pump to bypass, or with my luck, you'd break something unanticipated -- such as a lift arm mounting point. :laughing:

Damage a lift arm mounting point, or rollover bar, or QA plate? Why, that would be inconceivable!

 

[Gravy]

I still haven't given the new engine a real workout, but I used the forks to move some stuff around today. That reinforced my initial impressions. For the old Chevy and Ford guys: 305 vs. 454, or 302 vs. 460. There is actual off-idle torque.

 

[KentT]

LOL... I'd forgotten all about breaking the rollover. That happened when I was running the 22ci Char-Lynn wheel motors and the minihoe. The 28ci ones are the ones that have caused serious carnage...

I think you'll find that extra power quite useful -- I'm envious@

 

[J_J]

Makes you wonder if you had more HP available, and you did not back off the pedal as you would with the lower HP engine, would the pump be able to handle the added HP or blow up? Or bypass, I mean. Since none of us have apparently ever hit the bypass on the tram pump, lets add some more HP and push them till they bypass, then back off the HP. Right? :laughing:

The pump will extract enough HP to do the job if the HP is available.

The relief valves should protect the pump if set correctly.

If you are not running all the pumps at maximum potential, you should hare spare HP available.

With more HP, you may prevent the engine/pump system from stalling, but the system will still relieve at the same pressure. You still have the same torque.

Larger wheel motors should generate more force, but you still need the HP. You should be able to do more work.

Your speed may drop, but you can counteract that by larger diameter tires.

 

[J_J]

LOL... I'd forgotten all about breaking the rollover. That happened when I was running the 22ci Char-Lynn wheel motors and the minihoe. The 28ci ones are the ones that have caused serious carnage...

I think you'll find that extra power quite useful -- I'm envious@

I don't understand the relation to the wheel motors and a cyl operating the rollover arm.

Now, if you buried the mini-hoe and tried to move the machine with valve lever in neutral, then the mechanical force on the cyl might damage the cyl, hose, or valve.

You need a crossover relief valve in that situation.

 

[SpringHollow]

More torque on the wheel motors is putting more stress on all of the structural components of the loader when using the mini hoe and backing up with it buried. That and lifting/swinging large unbalanced loads are when I certainly feel I am doing the most damage to the loader.

Ken

 

[KentT]

More torque on the wheel motors is putting more stress on all of the structural components of the loader when using the mini hoe and backing up with it buried. That and lifting/swinging large unbalanced loads are when I certainly feel I am doing the most damage to the loader.

Ken

Exactly....

The first time I damaged my PT was with the original 12.5ci wheel motors when I was moving quickly, scooping up and hauling tree trunks while my son was sawing the trees down. I'd drive and scoop the tree trunk up with the grapple bucket, often pushing the trunk into another pile of trunks or brush to fill the grapple bucket. I encountered a tree trunk that was not completely sawn off, and was still attached to the stump. When I attempted to lift it, while still moving forward, one end lifted freely, while the end at the stump was still attached and did not break free. The PT puckered, lifting the back tires off the ground, and because I was attempting to turn at the same time, it continued to articulate, swinging the back end to the side, while still in the air... I bowed and bent the lift arms to the point that one side rested almost an inch lower than the other...

When I broke the original rollover bar (later replaced with the larger version) I was using the minihoe digging planting holes in the edge of the woods, on a slope where there were extensive tree roots. Attempting to pull back and break a root with the hoe (while it was still down in the hole), the front tires lost traction (due to downforce on the loader arms) and the front of the PT slipped sideways violently putting unexpected twisting force on the hoe and loader arms...

I'm not sure of the exact time that I've bent the QA attachment plate either time (it was only discovered later when changing attachments), but both times I was using the minhoe digging in rocky soil on slopes. I'm trying to break the bad habit of using reverse to help fill the bucket on the hoe in these circumstances, and rely on just curling the bucket -- but it's a challenge... because it is SO much faster to put back-pressure on the bucket as it curls closed to get the largest possible bite... Combine that with fact that the second time was while I was digging a deep (3' plus) trench for a drain tile, and much of the time the bucket was down in that trench and could not readily move sideways while the PT was inching forward or back...

I don't know how much you've used a minihoe on a PT, but it is NOT like using a true backhoe, where the machine is sitting still and all the work is done with hydraulics of the boom and bucket. With the PT, you're almost constantly moving the machine since you must articulate it to dump the bucket of soil, then reposition for the next bite...

You could describe all these as "operator error" -- but the point I was trying to make is that he will have more power available than the PT was originally designed to handle and it can show up at several different stress points on the machine...

 

[SpringHollow]

I have a swinging mini hoe that I even tweaked. I was pulling out felled trees for firewood. There was one tree that was in between two other trunks and the end was just sticking out. (A little larger than the limb in the original post about the swinging mini hoe http://www.tractorbynet.com/forums/power-trac/226274-swinging-backhoe-grapple.html?highlight=swinging ). So I grabbed it with the mini hoe bucket and thumb and used the swing of the mini hoe to pull it out a few feet and repeated until the 30' tree was out. I noticed the bucket was not working correctly and looked. The metal ear on the bucket that the pin slips into had bent due to the lateral forces and the pin had popped out. So the bucket was pivoting on a pin supported only on one end. Fortunately, I had a torch by then and could bend the metal back. Now I am a little more careful (well, ok, I think it might not be a good idea but go ahead and do it any ways).

 

[J_J]

Your fault if you dragged the bucket with the wheel motors.

Your machine, so use it to your ability.

 

[KentT]

JJ -- I already said my failures could be attributed to operator error. I don't know what more I can say -- nor do I understand the point of your post. I'm not blaming anyone but myself, but I still do not regret the upgrades I have made.

My caution is the machine with a larger motor will likely now have more power than its original design limits, which can lead to unexpected failures. In similar circumstances, the original 12.5ci wheel motors would just sit and whine, while these larger ones will spin one or more tires any time I'd like when pulling or pushing hard -- without ever bypassing, as far as I can tell...