Eliminate the air/oil pump

[aw113sgte]

I've seen a people do this a little but not too much quantitative info. Can the manual pump supply enough fluid with its tiny reservoir for both the cab raise and tire lower?
Just from glancing at the volume, seems like it would run out of fluid with just one of these operations-if it could even do one. I know it recirculates but if comes down to the volume difference of the rod during extension.

 

[Ronmar]

The 1” rod diameter does not really displace that much fluid. For instance when you lift the cab you send .19 gal to the cylinder and because of the rod, it only returns .14 gal to the reservoir. The difference being around .05gal.

The hand pump reservoir ID is ~3.75 X 3.75 X 3.25, or 45 cu/in? 45 cu/in works out to be ~.195 gal, so plenty to do both cab and tire…

the issue with that hand pump is that it is such low displacement(~.25 cu/in) and only single acting(only pumps on the downstroke). I initially contemplated using it but 168 pump strokes to get the cab over the balance point seemed like a lot.

I found a prince wolverine 1.5 cu/in hand pump that is dual acting, to use on my system. .75 cu/in lever down and .75 lever up, so it lifts the cab in 28ish pump strokes. I have some U tube videos on it, it works great. With an added diverter valve it could easily do both cab and tire Replacing both pumps and the control valve. Utube username Rronmar. I have a drawing somewhere showing the dual system with appropriate part numbers…

if you use the existing pump all by itself(no AOP) you will have to modify it slightly and add a vented filler plug. As it is installed in the system, the hand pump is completely sealed. As you pump fluid out it pulls a vacuum in the reservoir and on its return port, to insure it Can draw makeup fluid from the vented AOP reservoir. No aop, no vent, so you must provide one…

 

[aw113sgte]

Yep saw your video, nicely done.
Looks like 35 in^3 is the usable volume of the stock pump:


Cab lift 2x 1"dia x 16(max)" stroke
Tire lift 1"dia x 18(max)" stroke

(16*2+1*pi*0.5^2 = 39.3 in^3 needed for both at full extension

The actual stroke is a little less that then values above but I went on the side of caution. Those numbers look right?

 

[aw113sgte]

Looks like there is one with the same specs and a 65in^3 reservoir

 

[Ronmar]

Yep saw your video, nicely done.
Looks like 35 in^3 is the usable volume of the stock pump:
View attachment 910253

Cab lift 2x 1"dia x 16(max)" stroke
Tire lift 1"dia x 18(max)" stroke

(16*2+1*pi*0.5^2 = 39.3 in^3 needed for both at full extension

The actual stroke is a little less that then values above but I went on the side of caution. Those numbers look right?

Hmmm. Something might be up with that calculation. Area is pi X R squared, so .5 X .5 X 3.1416 = .7854 sq/in for a 1” rod cross sectional area. That X 33” stroke = ~26 cu/in total displacement for that extended rod length.

35cu/in is plenty for both, but in reality, how often do you anticipate doing both simultaneously?

 

[aw113sgte]

Hmmm. Something might be up with that calculation. Area is pi X R squared, so .5 X .5 X 3.1416 = .7854 sq/in for a 1” rod cross sectional area. That X 33” stroke = ~26 cu/in total displacement for that extended rod length.

Yep, same numbers, I did it for both 16" stroke on cab, plus the tire 18" so 50" total
50"*.7854= 39.2 in^3

 

[Ronmar]

Power packer made a bi-directional version of that pump, with a directional control valve to the right of the pump handle. Add to that a two-way diverter and some flow control and you can also do away with that large manifold valve Just like I did. In the end I didn't like the small volume of the power packer single acting pump. I have a similar version of the Prince pump I used on a dump trailer that has been in service for years, so thought that type pump would work well and it does Here is the drawing with the diverter part number, but it requires a pump with a directional control valve…

 

[Ronmar]

Yep, same numbers, I did it for both 16" stroke on cab, plus the tire 18" so 50" total
50"*.7854= 39.2 in^3

Uuuh where are you getting 50”? 16 + 18 = 34”… and I am pretty sure the cab lift is only 15” of stroke, so I uses 33” of stroke to come up with 26cu/in of rod displacement…

 

[aw113sgte]

Uuuh where are you getting 50”? 16 + 18 = 34”… and I am pretty sure the cab lift is only 15” of stroke, so I uses 33” of stroke to come up with 26cu/in of rod displacement…

Cab lift uses two cylinders.

 

[Ronmar]

Cab lift uses two cylinders.

On what truck?

 

[aw113sgte]

On what truck?

All A0 and A1 FMTV have two cab lift hydraulic cylinders
Edit: nope they don't! Just one

 

[Ronmar]

All A0 and A1 FMTV have two cab lift hydraulic cylinders

No they do not, single lift cylinder passenger side ~15” of stroke… the steering box occupies that space on the drivers side…

 

[Wingnut13]

Ahhh great, now I’ve got to go find where my drivers side cab lift cylinder went off to….

And just when I thought I was getting this truck sorted.

 

[aw113sgte]

No they do not, single lift cylinder passenger side ~15” of stroke… the steering box occupies that space on the drivers side…

Seriously? Dang I need to look at my truck, I never considered they would have such an imbalance.
Sorry completely my mistake.

 

[Reworked LMTV]

Ahhh great, now I’ve got to go find where my drivers side cab lift cylinder went off to….

And just when I thought I was getting this truck sorted.

The Driver's side hydraulic cylinders migrate South every Fall. Saw it on National Geographic.....

 

[aw113sgte]

Makes sense why my cab never comes down straight and shifts when it hits the latch.

 

[Ronmar]

Makes sense why my cab never comes down straight and shifts when it hits the latch.

Thats because your pivots or front bushings have an issue. If everything it tight and right, they go up and down square on one cylinder…

 

[GeneralDisorder]

Makes sense why my cab never comes down straight and shifts when it hits the latch.

That's usually because the latches aren't aligned correctly. From experience with my truck, this is a huge issue with the A1R specifically because the design of the cab latch mounting bracket (no cab air suspension) is..... terrible is the only way I can describe it. I had to manufacture two shims for my bracket to get my cab to close straight and not put unnecessary angle and side load on the pin mount. Mine was so badly aligned from the factory that the latch hydraulic pin lock wouldn't engage and the whole cab would shift in the neighborhood of 1" left to right when the pin went into the latch. Another owner I know with an A1R got his truck because of a bunch of electrical system damage when the cab latch mount disintegrated and the cab shorted out the wiring on the LBCD.

 

[littlesfmtv]

That's usually because the latches aren't aligned correctly. From experience with my truck, this is a huge issue with the A1R specifically because the design of the cab latch mounting bracket (no cab air suspension) is..... terrible is the only way I can describe it. I had to manufacture two shims for my bracket to get my cab to close straight and not put unnecessary angle and side load on the pin mount. Mine was so badly aligned from the factory that the latch hydraulic pin lock wouldn't engage and the whole cab would shift in the neighborhood of 1" left to right when the pin went into the latch. Another owner I know with an A1R got his truck because of a bunch of electrical system damage because the cab latch mount disintegrated and the cab shorted out the wiring on the LBCD.

Now I have something to think about when I get to the house. I Haven't really paid attention to the amount of shift my cab has when closing...... I just stare at the pin on the latch to make sure it locks. I had not heard that A1R trucks have this issue.

 

[olly hondro]

I deleted the pump because I 86'd the spare tire deployment mechanism + the suck down cylinders + cab tilt feature = why keep it?