Blowing hydraulic hose solution

[john p]

Gearbox driven, worst case scenario is I get a beaver power pack and run the mewp under its own steam, can’t change the pump because it runs the massive winch.

[aspenarb]

30 minutes ago, john p said:

Gearbox driven, worst case scenario is I get a beaver power pack and run the mewp under its own steam, can’t change the pump because it runs the massive winch.

 

You could change the pump you have for a twin, one large section for the winch and a smaller piggy backed for the mewp.

Just thoughts.

 

Bob

 

[openspaceman]

On 11/09/2018 at 22:28, aspenarb said:

You could change the pump you have for a twin, one large section for the winch and a smaller piggy backed for the mewp.

Just thoughts.

If the chassis is a gearbox driven PTO from something like a tipper wouldn't it be a swash plate axial pump?

 

I think it would be sensible to see how the MEWP circuit works from a powerpack just  to judge the flow rate needed.

 

The business about the spool getting stiff does seem to be that it is not rated for the flow and one part of the block is getting hotter than another, the differential expansion then putting a bending pressure on the spool, this will lead to premature wear of the spool in its bore.

 

I have said in the past that I don't like pressure compensated spool flow dividers as they tend to heat the oil  on frequently used circuits. There is another type  which is a bit like two motors on a single shaft like the tandem pumps Bob showed. They are called internal flow gear dividers and they pass a fixed proportion of the flow to one service without increasing the pressure to the other service (which can just be dumped to tank). So even with the existing axial piston pump (which works at  a higher pressure than aluminium "Dowty" gear pumps )  a small part of the flow can service the MEWP  and can be switched back to recombine and power the winch.

[john p]

Here’s the pump (apologies for poor quality) mewp max pressure is 200bar, pump looks like it’s capable of a fair bit more ( plate doesn’t give pressure rating)

[john p]

Here’s the pump (apologies for poor quality) mewp max pressure is 200bar, pump looks like it’s capable of a fair bit more ( plate doesn’t give pressure rating)

[john p]

Here’s the pump (apologies for poor quality) mewp max pressure is 200bar, pump looks like it’s capable of a fair bit more ( plate doesn’t give pressure rating)

[john p]

Here’s the pump (apologies for poor quality) mewp max pressure is 200bar, pump looks like it’s capable of a fair bit more ( plate doesn’t give pressure rating)

[john p]

Here’s the pump (apologies for poor quality) mewp max pressure is 200bar, pump looks like it’s capable of a fair bit more ( plate doesn’t give pressure rating)

[openspaceman]

3 hours ago, john p said:

Here’s the pump (apologies for poor quality) mewp max pressure is 200bar, pump looks like it’s capable of a fair bit more ( plate doesn’t give pressure rating)

I don't think pressure is the issue so much as flow. That pump delivers too much flow for your MEWP spool block to handle, hence why I suggested a flow divider.

 

The other possibility is that when the MEWP circuit was connected the main pressure relief for the original pump and winch was bypassed.

[john p]

I don't think pressure is the issue so much as flow. That pump delivers too much flow for your MEWP spool block to handle, hence why I suggested a flow divider.
 
The other possibility is that when the MEWP circuit was connected the main pressure relief for the original pump and winch was bypassed.

Yes, that makes perfect sense, the pipes on the mewp properly jump/kick out when switched over, I suppose it’s like the m3/303/single carriage way scenario, large flow getting channeled into small pipe!