0351 wrote: ↑
Sat Jun 05, 2021 12:08 am
Sorry, I meant problems with the model 6/7 overheating. Haven’t read anything about the 11s having problems. The Eaton 11 manual has the shows the option of using a reservoir and cooler for some applications.
The Eaton series of pumps of which the model 11 is a member, are, like all hydraulic pumps with aluminum housings, not very efficient as loading nears maximum ratings. Ergo
they have a natural tendency to run hot. They are mostly intended for moderate loading, with occasional peaks. Gear pumps with iron housings are considerably more efficient under heavy loading.
If you use an Eaton 11, I highly recommend you include a radiator of some sort in the return line to the reservoir. Continuous oil temperature should not exceed 150º F, and short-term temperature should not exceed 200º F, even if using a synthetic. The problem has less to do with heating the oil and more to do with what happens to the pump when it gets too hot. Seals can fail and the difference in expansion rate between the steel pump components and the aluminum housing will produce internal blow-by and a marked loss of efficiency.
In determining oil reservoir capacity, one gallon for every three horsepower applied to the pump is the minimum ratio I use. In your application, that would work out to a four gallon reservoir. The reservoir should be filled to no more than 85 percent capacity to allow for expansion and to discourage aeration that can lead to damaging pump inlet cavitation. A bigger reservoir won't necessarily aid cooling, since it will be enclosed by the locomotive's carbody and thus not able to freely radiate to the air. The reservoir's primary role in any hydrostatic power transmission is to prevent pump starvation under any condition, not to dissipate heat.
An accessory automatic transmission radiator suitable for a full-sized pickup truck or an SUV of a Chevy Suburban's size makes for a good radiator—bigger here is definitely better. The radiator should be inserted in the return line upstream of the filter. You might also want to consider fan-cooling the radiator.
I realize that by using right angle gear box’s I’ll be loosing some power.
Any type of power transmission device will have parasitic losses. As geared devices go, the efficiency of the Tolomatic product is fair to good, depending on speed and load. Tolomatic right-angle units use intersecting helical gears that are cut with a 45 degree helix, resulting in a lot of sliding action between meshed teeth. I've seen 75-80 percent efficiency quoted for these gearboxes under full load, although I haven't personally used them in anything. Just for perspective, helical gears operated on parallel shafts typically exceed 90 percent efficiency under full load, since they are cut with smaller helix angles and have true conjugal action that minimizes sliding between teeth.
Under ideal circumstances, a hydrostatic power transmission system consisting of a fixed-displacement pump, fixed-displacement motor, and required flow-control valving, will achieve a maximum efficiency of around 70 percent if most of the plumbing is done in tubing instead of hoses. Hoses greatly hurt efficiency, and thus tend to make the system run hotter. The only places you will find hose in my F-unit's propulsion system is at the trucks—and these are short hoses, at that. Everything else is plumbed in steel tubing.
Efficiency with common variable-displacement pumps may reach the 70 percent level with the pump operating at maximum displacement, but will quickly deteriorate at lower displacements. YMMV, of course.
Something to consider in driving the trucks through shafts and gearing from a chassis-mounted source is the torque reaction that will be generated. Under heavy loads, torque reaction will cause the locomotive to roll to one side, same way a rear-wheel-drive automobile rolls to the right under acceleration. You may find this to be undesirable. This behavior won't occur with hydraulic motors mounted in the trucks and geared to the axles (geared meaning a roller chain drive—actual gearing would be unneeded extravagance, in my opinion). The torque reaction will be absorbed within the truck itself.
Hydro motors in the truck aren’t out of the question. I would need to come up with a way to connect a pump to the HST the route hoses to the motors? My commercial zero-turn diesel mower uses a 28hp cat that powers a hst and hydro motors at the wheels.
I would go that route, but as I said above, keep the hose to an absolute minimum.