Valve help

[balsam]

I am planning on building a tracked vehicle that I can use for ice fishing. I have a circuit in mind that should operate like braked steering used on most of them. Normally a differential is used and each output shaft is braked to slow or stop the track causing the other to turn faster, thus turning the vehicle.
Often, using hydraulics, tandem variable displacement pumps are used to individually drive each side which allows for a zero turn radius, something I don稚 need. Totally stopping one side will allow me a turning radius the width of the machine.
I think I can achieve results similar to the differential system hydraulically, with a variable displacement pump, driving wheel motors in parallel. By restricting flow through one side or the other, the restricted side will slow causing increased flow to the opposite, causing the turn.
I have worked out most of the kinks, like reversing, and where to place the restrictions(metered out) but I can稚 think of a flow control valve that I can use. I need to be able to vary the flow from full to nothing, hopefully using a joystick or wheel.
There must be a valve of some kind that I can even modify to do it.
Hopefully I have explained my problem and someone can help.
I may try to figure out how to add a schematic of the circuit on here.
Thanks in advance

 

[ptsg]

What about a hydraulic ball valve for each motor? With a linkage to a steering wheel, probably a couple springs.

It would be installed on one of the lines for the hydraulic motor, same for the other motor. It would work for either forward or reverse.

I'm just not sure about the metering capability for the ball valve. I don't think it's a big deal and can also be adjusted with the linkage, to make it easier to control.

By fully closing the ball valve on one side, would lock the motor on that side, causing the vehicle to turn.

 

[balsam]

I think you’re on to something there! I never thought of something that simple....love it.
I think they completely close at 1/4 of a turn and I just saw, online, that they do come in a high pressure variety.
I could simply replace the lever with a longer “joy stick” and have it spring returned to fully opened, which I think is what you are suggesting.
Great idea...love the simplicity of it.
I know I a losing some efficiency if I use hydraulics but it allows me so much more flexibility in the overall design. The fact that everything will be lighter should offset that a little.
Thanks again.

 

[ptsg]

It's also way cheaper than a "true" flow control valve.

It will, however, act like a differential in the way that when fully closed, the other side will get the full flow (instead of being shared by 2 motors) and spin faster. That's also easy to compensate in the variable pump control lever.

Keep us posted on this project. Sounds really interesting. Since I have this thing for tracked vehicles, I'm even more interested. I've built a half track backhoe and had two old small tracked tractors in the past.

 

[aczlan]

There are two options, one would be to use a flow control valve such as: 1/2 NPT -16 GPM Wolverine Flow Control Valve w/Relief Valve | Flow Control Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
That will divert the excess flow to the tank and the "outside" track should stay spinning at about the same rate.
The other would be a ball valve such as: 1/2" NPT Carbon Steel 725 PSI Ball Valve | Ball Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com
That would force the excess flow to the other side and make that track speed up.

Aaron Z

 

[balsam]

I would love to sit down with you over a beer to discuss this(I’ll buy). Years ago I was involved in a ski operation and we used a Thiokol Imp to groom the hill. If I remember correctly, the Imp had a 4 cylinder engine with two, back to back, transmissions.....was powerful but weighed tons. It used the differential and braking system. I have always thought of building a smaller, much lighter two person vehicle for ice fishing. As I get older, sitting on a snow machine in the cold is no longer fun.
I Would like it to have a heated cab and for it to semi-float(long enough to get out of a hatch in the roof if I go through the ice). I may be able to make it amphibious.
I did a lot of calculating speeds, torques and horsepower to power a machine in the 2250 lb. range with a 600lb payload running up a 60% grade and a maximum speed of 25mph. Of course it would just crawl up that kind of grade.
Interesting, that when I do any searches for vehicles like this, it’s always Russian stuff that comes up. Those guys are crazy about them.

 

[DLTTrekkers]

Reinventing the wheel ?

 

[balsam]

Thanks Aczlan.
I will be in the 20gpm so would have to use 3/4” lines and hardware but am sure ones like you recommend are available. Yeah, bleeding fluid off may be a better way to approach the flow control because I did wonder how badly, sending twice the fluid to one side on a full turn, would spin the machine. At my age the G’s might do me in. Of course I can control the flow by the pumps swash plate but then it’s two operations...going to look into that.
I have a 40hp. Kohler gas engine in mind which means I have to use an electric cab heater. I would rather use a water cooled 3 or even 4cyl. But there is so much difference in physical size and weight.
You guys are giving me lots to think about.

 

[balsam]

DLTTrekkers
To me, it’s a brand new wheel.
If you can’t be helpfull perhaps you should not respond to these threads.
You are not being nice.

 

[aczlan]

Thanks Aczlan.
I will be in the 20gpm so would have to use 3/4” lines and hardware but am sure ones like you recommend are available. Yeah, bleeding fluid off may be a better way to approach the flow control because I did wonder how badly, sending twice the fluid to one side on a full turn, would spin the machine. At my age the G’s might do me in. Of course I can control the flow by the pumps swash plate but then it’s two operations...going to look into that.
I have a 40hp. Kohler gas engine in mind which means I have to use an electric cab heater. I would rather use a water cooled 3 or even 4cyl. But there is so much difference in physical size and weight.
You guys are giving me lots to think about.

If you look at the links that I posted, they also carry the same valves in a 3/4 inch, 30GPM flavor and some of them larger as well.
For heat, given that you will have lots of hydraulic flow and heat, you might look at using a cooler in the return line as a heater core to heat your cabin.
If you wanted to use a steering wheel, you could use a setup like a boat steering wheel with cables or ropes attached to it and then to a spring and have that pull the levers for the flow control valves.

Aaron Z

 

[ptsg]

Reinventing the wheel ?

Just the feeling you get to see a complex project that you built all by yourself, working as you want, makes it all worth it IMHO. To me, it's just priceless. And I know what I'm talking.

It's not always about the money, but more about being able to do it by yourself and to test yourself with hard challenges... It's easy to go out and just buy it. But where is the fun of that? Plus you get to make it the way you want and need it.

 

[CADplans]

Is your design going to use an open center type gear pump for flow? (a fixed displacement pump)
If so, any restriction to the oil flow converts all the oil not going to the hydraulic motors directly to HEAT!!

If you have 20HP driving a suitable size pump, and restrict the flow by 50% for half speed,,,
10HP will be directly heating your hydraulic oil.

To restrict flow, you need the type pump that is used on closed center hydraulics,,
that type pump produces variable flow rate, based on demand, open the valve more, the pump generates more GPM,,,

 

[balsam]

Cadplans
It will be an axial piston, variable displacement pump. This greatly reduces heat generation as the flow rate is determined by the pumps swash plate angle. Of course there is always heat build up from the “charge pump”, pump slippage, etc. I may not use a closed loop circuit, eliminating the charge pump and create reverse with a directional control valve.
A little heat will be generated from the steering valves but using the “bleed off” valves that were suggested earlier, heat will be minimized as the fluid is dumped at system pressure and not relief pressure.
I like the idea of using the oils heat to heat the cab. Perhaps an electric/oil hybrid system.
Usually if the reservoir is big enough heat is not a factor. I once designed a system to drive a snowblower and because the oil was so cold and viscous, it kept blowing the case seals out of the motor, despite the being a case drain...has to put a heater on the reservoir. Jeez!

 

[balsam]

Well said! I have been looking into a project, to keep me busy and this seems like a lot of fun.
I have gotten a lot of great ideas already from you guy. Over the next couple of days I will sit down and think about this stuff.
So much stuff invoved with this project. I would like to start the actual construction, the beginning of January.

 

[oldnslo]

If you using one pump and motors in parallel you can not use a bleed off circuit unless you have a flow divider. Reason for this is oil will take the path of least resistance and all of the oil will bleed off slowing down both tracks.

A benefit of the meter in approach is you potentially still have power to both tracks so you can power steer. Sometimes this might be helpful.

Good luck on this project

 

[balsam]

If you using one pump and motors in parallel you can not use a bleed off circuit unless you have a flow divider. Reason for this is oil will take the path of least resistance and all of the oil will bleed off slowing down both tracks.

A benefit of the meter in approach is you potentially still have power to both tracks so you can power steer. Sometimes this might be helpful.

Good luck on this project

Yeah, I thought of that overnight. I haven稚 sat down to draw out a diagram yet but I will today. I see I would have to use a flow divider and not sure I want to do that. I知 also wondering if it痴 best to meter the fluid into the motors, or out of them as the slower track would become an overrunning load as it slows??
I would love to use tandem pumps but the cost is exorbitant and I don稚 like the added weight. I seem to find lots of singles in my hp range but not doubles.
I知 trying to keep is as simple and light as I can.
Thanks for your insight. You know your stuff.

 

[balsam]

OLDNSLO
Also, if I do use metered out, the overrunning track would drive the motor on it like a pump so I would have to use relief between the pump and flow control......probably, what I call, a shuttle valve. Not sure that’s the proper term.
Does that make sense?

 

[thepumpguysc]

I might be way off base here so feel free to ignore it..
I was cruzing around face book the other day & this short video popped up showing a small SUV{front wheel drive} backing into some tracks..
Then they pulled forward & drove into more tracks.. THEN it showed the suv hitting a snow pile & going off road.. like a snowmobile..
U strap these tracks onto your existing wheels & let the machines wheels do all the work via rollers that generate the power to the tracks..
It was very kool.. I don't get snow but if I did.. oh brother, I'd have me a set..
I'm sure they would work on a nice cabbed, heated ATV.?? Go do a search..

 

[farm boy00]

For both steering and direction control (fowards/reverse) why not use a 2 spool motor directional control valve?
Only problem would be some sort of brake because a motor spool valve let's the motor free wheel

Heres a link for one from surplus center.

2 Spool 25 GPM RD522EEAA5A4B1 OC Motor Spool Valve | Directional Control Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

 

[aczlan]

If you using one pump and motors in parallel you can not use a bleed off circuit unless you have a flow divider. Reason for this is oil will take the path of least resistance and all of the oil will bleed off slowing down both tracks.
A benefit of the meter in approach is you potentially still have power to both tracks so you can power steer. Sometimes this might be helpful.
Good luck on this project

Incorrect. The one I linked to (1/2 NPT -16 GPM Wolverine Flow Control Valve w/Relief Valve | Flow Control Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com) is a Pressure compensated flow control valve, the fluid going to the excess flow port has to go through a pressure relief valve first.

Aaron Z