PT Rises from the Ashes

bmkar · Sep 15, 2003

( I'm running the hydraulic cooler fan backwards (cause I accidentally hooked it up backwards and this gives me a chance to test whether the concept will help reduce chaff getting into the engine compartment) )

John,
That's something I've been wonderin' about, too...but then I complicated it (on the design napkin) with a dpdt switch (or relay) so the fan could be reversed "for cleaning"...now you've got me thinkin' /forums/images/graemlins/shocked.gif that there would be real cooling benefits to permanently running it backwards.

Bob999 · Sep 15, 2003

( I'm running the hydraulic cooler fan backwards (cause I accidentally hooked it up backwards and this gives me a chance to test whether the concept will help reduce chaff getting into the engine compartment) )



I will be interested in the results. I have no problem with chaff since I taped screen over the rear panel of the enclosure and changed to a side discharge mower deck. I get some chaff on the screen material in a circle that exactly corresponds to the intake for engine radiator air cooling but it simply brushes off. I have not had build up on the hydraulic oil cooler since the changes.

One thought about running the fan reversed--if you do get chaff it will be much more difficult to clean.

Sedgewood · Sep 15, 2003

Bob999 My understanding is that PT units have a SUCTION line filter for the variable displacement pump. 

That's what my unit has.

 My further understanding is that PT units have no filtering on the PTO and auxiary PTO circuits and that they have no suction line screens anywhere in the system. 

Right.

Sedgewood

bmkar · Sep 16, 2003

( if you do get chaff it will be much more difficult to clean )

Good point...Ahh...Now, with a short wood/metal framework over the top of fan with house screening attached and held on with strip magnets (fridge door style) we'd keep positive pressure in the engine bay(keeping it cleaner) and maybe a cooler (??) environment for engine...
...Not sure if the "clean" factor would be worth the effort , but, a cooler operating environment for the motor would be a worthy goal(??) /forums/images/graemlins/wink.gif

Bob999 · Sep 16, 2003

but, a cooler operating environment for the motor would be a worthy goal(??) 

It seems to me that what is important is that you have cool clean air going to the engine air cleaner and to the engine cooling. On the diesel power units both the air cleaner and the intake for engine cooling are located at the back of the tractor. I think there is a good chance the temperature of the air there would be increased by running the fan backward.

Edward_DiMaria · Sep 16, 2003

Do these circuits get sort of "indirect filtering"
since all the fluid in the tank is filtered and that is where
they get the fluid? or is that a stretch?

would it be easy to add and inline filter or would it mess up the flow / pressure? - what are the different types of filtering techniques? - does anyone know - ??

Bob999 · Sep 16, 2003

would it be easy to add and inline filter or would it mess up the flow / pressure? - what are the different types of filtering techniques? - does anyone know - ??


I have looked in the engine compartment of my PT 1845 for a place that a filter might be added on the return line of the PTO circuit. This is a 15 gal/min circuit and I have assumed I would use the same size filter that PT uses on the suction line for the variable displacement pump. I haven't come up with a place to put it. I have read that suction line filters are not generally recommended---except--for variable volume pumps.

There are both low pressure (return line) and high pressure (supply line) filters available. Both Grainger and MSC Industrial Supply carry both. High pressure units are much more expensive ($300+) than low pressure ($~70).

 Do these circuits get sort of "indirect filtering"


PT uses a common reservoir for all hydraulic circuits. The variable volume pump pulls from this reservoir and the return flow is to the same reservoir. My understanding is that this approach is supposed to maintain an "acceptable" cleanliness level. What this approach does not do is ensure that the supply to the other two circuits is clean--this can only be done with suction filters for each of those circuits. It also does not ensure that dirt from any circuit return is kept out of the common reservoir--this can only be done with a return line filter on each circuit. Putting a filter on the supply side ensures that any dirt is filtered before it gets to the motor or cylinder.

Clearly there is a point of diminishing marginal return with adding filters to the system. PT engineers made the choice at one filter in the system of three pumps. No one has really provided any quantitative information about what would be gained from adding an additional filter.

MossRoad · Sep 16, 2003

No one has really provided any quantitative information about what would be gained from adding an additional filter. 

Measurable gain... no. But if something in any of the hydraulic circuits shreds itself and dumps it into the reservoir, all of the unfiltered circuits will be open to damage. So how do you measure peace of mind? /forums/images/graemlins/wink.gif

Sedgewood · Sep 17, 2003

Bob999: I will be interested in the results. I have no problem with chaff since I taped screen over the rear panel of the enclosure and changed to a side discharge mower deck

Guess it's about time I added something here since I seem to have started this discussion about chaff filtering. /forums/images/graemlins/tongue.gif

My mowing is probably a bit different from most, especially this year since I just started the mowing season last week /forums/images/graemlins/tongue.gif

Let's start with a picture from yesterday after 1-1/2 hours into brush hogging an unmowed field. And not a terrifically heavy chaff day at that - the growth didn't include much dry grass es- mostly mature goldenrod etc.

 I get some chaff on the screen material in a circle that exactly corresponds to the intake for engine radiator air cooling but it simply brushes off. I have not had build up on the hydraulic oil cooler since the changes. I say a light chaff day yesterday because I only had to brush off the rear screen half a dozen times in the 1-1/2 hours - instead of the usual double that.

One thought about running the fan reversed--if you do get chaff it will be much more difficult to clean.

I'm not sure it makes much difference - once I determined my cooler was full of last years chaff, way deep inside where you can't see it, it took nearly an hour with the hose to wash it clean. That's from last years stock non-reversed fan setup.

Sedgewood

Sedgewood · Sep 17, 2003

bmkar: Good point...Ahh...Now, with a short wood/metal framework over the top of fan with house screening attached and held on with strip magnets (fridge door style) we'd keep positive pressure in the engine bay(keeping it cleaner) 

Kind of like this? What you see is a screened "house" (with a solid roof - screens on sides only) taped on the hood. Inside is a piece of furnace filter material lying atop the fan. In the center is a trumpet bell shaped piece of aluminum I thought might redirect the flow.

 ...Not sure if the "clean" factor would be worth the effort , but, a cooler operating environment for the motor would be a worthy goal(??) 

Blowing 150 degree air over the engine doesn't seem to help the cooling much. It's running hot as ever.

Sedgewood