Anyone wanna help with a project most call crazy?

[619atv]

Those welds look fine.
One thing i'd do is to weld in gussets forward, you don't want any flex in it when you move the steerling levers. The OEM one is made from pretty thick steel.
If you can't get a picture, let me know. I have a 763 cooler at my parents place that is removed so easy to take a picture.
As long as the cooler you choose can handle the pressure, 120psi or so is needed.

I dont see a return to the resivoir on this schematic just wondering.......so i do not have the block where all the returns gather i think its called the replenishing valve? And my motors dont have the case drain...is that gonna be a problem? ive been looking at what i got and i can work it a few ways but had a couple questions first... It looks like the replenish feeds back to the center of the pumps im guessing to help when your at close to and full stoke on drive motors? If so does this need to be pressurized? It looks like it comes from bottom of cooler so im thinking it is a low pressure? any and all thoughts appreciated

 

[619atv]

I dont see a return to the resivoir on this schematic just wondering.......so i do not have the block where all the returns gather i think its called the replenishing valve? And my motors dont have the case drain...is that gonna be a problem? ive been looking at what i got and i can work it a few ways but had a couple questions first... It looks like the replenish feeds back to the center of the pumps im guessing to help when your at close to and full stoke on drive motors? If so does this need to be pressurized? It looks like it comes from bottom of cooler so im thinking it is a low pressure? any and all thoughts appreciated

Sorry i misspoke the replenish valve is not the block and it does not run back to center....the block converges the returns and sends them to the suction tube mixing them with fluid from the resivoir i can get that done with a block i have from the stock case parts and a pressure compisated flow divider/combiner im mostly worried about the charge pressure switch and feed.....should it be pressurized?

 

[billrbg]

Sorry i misspoke the replenish valve is not the block and it does not run back to center....the block converges the returns and sends them to the suction tube mixing them with fluid from the resivoir i can get that done with a block i have from the stock case parts and a pressure compisated flow divider/combiner im mostly worried about the charge pressure switch and feed.....should it be pressurized?

Yes, the charge port (the line directly below #24) needs to be pressurized. Note that on the stock system ALL flow through the cooler and filter goes to only that port.

 

[619atv]

Yes, the charge port (the line directly below #24) needs to be pressurized. Note that on the stock system ALL flow through the cooler and filter goes to only that port.

 

[619atv]

So here is my system in a crude drawing I tried to label everything as clearly as possible..... As you can see I have three return lines I can play with....I figure the one that comes from the curl relief is gonna be used the least because it will only pump oil when bucket is curled too far correct? So if I merge the relief from the 3 spool valve and the curl relief I could send those to be merged with the suction line and that would leave me with the relief from the 1 spool valve to supply the charge pressure.....but what pressure should the charge line (relief from the 1 spool valve) have on it? This should also be the line I run through my cooler and filter correct? Can I use a relief valve somewhere after it leaves the 1 spool to regulate it down enough to be correct for charge pressure? Leaving me one last line I would return to tank...... I still am confused however by the schematic from the stock 743 as to how any fluid makes it back to your reservoir.....this dosent work like a puke tank in an automotive cooling system does it? Please help I'm sooo close Thanks......Rick

 

[billrbg]

So here is my system in a crude drawing I tried to label everything as clearly as possible..... As you can see I have three return lines I can play with....I figure the one that comes from the curl relief is gonna be used the least because it will only pump oil when bucket is curled too far correct? So if I merge the relief from the 3 spool valve and the curl relief I could send those to be merged with the suction line and that would leave me with the relief from the 1 spool valve to supply the charge pressure.....but what pressure should the charge line (relief from the 1 spool valve) have on it? This should also be the line I run through my cooler and filter correct? Can I use a relief valve somewhere after it leaves the 1 spool to regulate it down enough to be correct for charge pressure? Leaving me one last line I would return to tank...... I still am confused however by the schematic from the stock 743 as to how any fluid makes it back to your reservoir.....this dosent work like a puke tank in an automotive cooling system does it? Please help I'm sooo close Thanks......Rick

Yes, in the stock system the reservoir IS only for fluid make-up or expansion. There is no continuous flow through it and it has no cooling effect. That's why it can be fairly small. If there are no leaks even a quart or two will last for many, many hours; depending on how often you use the aux ports and lose a little bit each time there. If there is a leak of any consequence, then no reasonable size reservoir will be enough. That vane pump is something like 11 gal/min, isn't it? There is already a relief valve for the charge, built into the hydrostatic pump unit. It's that item #24 set for 85 psi. What isn't clear to me is where that charge relief discharges TO. I'm guessing it discharges into the pump case, further guessing that pump and the vane pump case are connected internally, and that the vane pump case is connected (again, internally) to the vane pump suction.

 

[619atv]

Yes, in the stock system the reservoir IS only for fluid make-up or expansion. There is no continuous flow through it and it has no cooling effect. That's why it can be fairly small. If there are no leaks even a quart or two will last for many, many hours; depending on how often you use the aux ports and lose a little bit each time there. If there is a leak of any consequence, then no reasonable size reservoir will be enough. That vane pump is something like 11 gal/min, isn't it? There is already a relief valve for the charge, built into the hydrostatic pump unit. It's that item #24 set for 85 psi. What isn't clear to me is where that charge relief discharges TO. I'm guessing it discharges into the pump case, further guessing that pump and the vane pump case are connected internally, and that the vane pump case is connected (again, internally) to the vane pump suction.

Your the man bill....I got movement!!! I worked with the hoses a bit and found the return from the 1 spool valve works perfect for the charge pressure...I hooked it up a couple different ways and they either sent my levers into convulsions or whined like crazy but I found the right combination can't even hear the pumps and wheels are perfectly responsive to the levers so I'm thinkin I got that part down....next is linkages and I got a few ideas will post pics when I redo a couple hoses and fittings (had to make what I had work so I will tidy up by looping off ends and recrimping the correct fittings) and pics of first draft on the linkages when I get them welded up...... Anyway just wanted to say thanks and I owe you a steak dinner....

 

[Tazza]

Your the man bill....I got movement!!! I worked with the hoses a bit and found the return from the 1 spool valve works perfect for the charge pressure...I hooked it up a couple different ways and they either sent my levers into convulsions or whined like crazy but I found the right combination can't even hear the pumps and wheels are perfectly responsive to the levers so I'm thinkin I got that part down....next is linkages and I got a few ideas will post pics when I redo a couple hoses and fittings (had to make what I had work so I will tidy up by looping off ends and recrimping the correct fittings) and pics of first draft on the linkages when I get them welded up...... Anyway just wanted to say thanks and I owe you a steak dinner....

Not fully sure what you are trying to do with the multiple reliefs. From what i understand from the bobcat setup, you have a control block that has fluid in from the pump, the outlet goes back through the oil cooler then filter, back to a port block that allows what is needed for the pump or excess to the reserve tank.
There are no extra lines from the cylinders, there is just one oultet port in the control valve that takes this fluid away.
Ideally, if you install a oil cooler, hook it up to the line that comes out of the control block

 

[619atv]

Not fully sure what you are trying to do with the multiple reliefs. From what i understand from the bobcat setup, you have a control block that has fluid in from the pump, the outlet goes back through the oil cooler then filter, back to a port block that allows what is needed for the pump or excess to the reserve tank.
There are no extra lines from the cylinders, there is just one oultet port in the control valve that takes this fluid away.
Ideally, if you install a oil cooler, hook it up to the line that comes out of the control block

Tazza the case hydraulics are set up a little different than the bobcat I have a three spool valve on my right side that controls the lift function and the two auxiliary circuits, front and rear....coming out of this spool setup I have a relief and a power beyond outlet...the power beyond feeds a 1 spool valve on my left side for the curl function and has another relief coming out of it as well......also I have a relief coming from the lines that run to my curl cylinders I think for when it is curled to max position......this leaves me with three reliefs......I do not have the block you are talking about I only bought the pumps Also just to note the case uses hand controls to work the lift and dump circuits so I had to play with my lines to get them correct....at first I tried to tie all the reliefs together and send them into the charge port but I think it was too much because the pumps howled like crazy so I swapped and changed everything around and found the correct setup.... I did work up one linkage today and it works well ill post pics soon

 

[billrbg]

Tazza the case hydraulics are set up a little different than the bobcat I have a three spool valve on my right side that controls the lift function and the two auxiliary circuits, front and rear....coming out of this spool setup I have a relief and a power beyond outlet...the power beyond feeds a 1 spool valve on my left side for the curl function and has another relief coming out of it as well......also I have a relief coming from the lines that run to my curl cylinders I think for when it is curled to max position......this leaves me with three reliefs......I do not have the block you are talking about I only bought the pumps Also just to note the case uses hand controls to work the lift and dump circuits so I had to play with my lines to get them correct....at first I tried to tie all the reliefs together and send them into the charge port but I think it was too much because the pumps howled like crazy so I swapped and changed everything around and found the correct setup.... I did work up one linkage today and it works well ill post pics soon

Just be sure you have charge pressure under all operating conditions. If it drops briefly from that 85 psi while you are moving the bucket or using aux ports it may not matter, but I would try hard to avoid that. The stock 743 Control Valve has, I think, all "closed-spool" valving with a relief by-passing, so that there is always flow and pressure available for fluid going back through the cooler, filter, and charge. If any of you valves connected to that vane pump are "open-spool", then you may lose charge pressure when they are in neutral. Clear as mud? Point is, be sure you have about 85 psi charge pressure all the time...

 

[billrbg]

Just be sure you have charge pressure under all operating conditions. If it drops briefly from that 85 psi while you are moving the bucket or using aux ports it may not matter, but I would try hard to avoid that. The stock 743 Control Valve has, I think, all "closed-spool" valving with a relief by-passing, so that there is always flow and pressure available for fluid going back through the cooler, filter, and charge. If any of you valves connected to that vane pump are "open-spool", then you may lose charge pressure when they are in neutral. Clear as mud? Point is, be sure you have about 85 psi charge pressure all the time...

I think I used wrong terminology in the post above. I meant "open-CENTER" and "closed-CENTER" for the directional control valves. They may, or may not, be spool valves (are on stock 743)

 

[7LBSSMALLIE]

Agreed, and I think it is not the hydrostatic drive that is making most of the heat, it is the vane pump for lift/tilt/aux. It doesn't take long for those lines to get pretty hot, even when the B'cat is sitting and not moving much (like jack-hammer or back-hoe work).

OK. now I see why you got a bucketful of xtra cost free parts. yea dude I feel you we can make this happen. glad to help. need concise description of problem at hand. might even have a few o the parts you need. (so you are goinig to make this happen) OK. I got youre back. I aint paying shipping. let me know what you need. glad to help .as a guy who put things back to factory specs. I find this project interesting. around thru over or under. the only easy day was yesterday. and so on. . keep us informed of what you need.

 

[619atv]

OK. now I see why you got a bucketful of xtra cost free parts. yea dude I feel you we can make this happen. glad to help. need concise description of problem at hand. might even have a few o the parts you need. (so you are goinig to make this happen) OK. I got youre back. I aint paying shipping. let me know what you need. glad to help .as a guy who put things back to factory specs. I find this project interesting. around thru over or under. the only easy day was yesterday. and so on. . keep us informed of what you need.

a href="http://s300.photobucket.com/user/619atv/media/Mobile%20Uploads/IMAG0053.jpg.html" target="_blank">

got linkages worked up i used 3/4 allthread across the bottom welding a coupler on both sides of the machine to screw into and a section of pipe that fit pretty good around the outside of the allthread......i welded my square tubing to the pipe for leavers and cut out some plate to make linkages im pretty happy with......wish i woulda took pics of them before i fished them under the pump for mounting (that was a pain but it can be done)

 

[619atv]

a href="http://s300.photobucket.com/user/619atv/media/Mobile%20Uploads/IMAG0053.jpg.html" target="_blank"> got linkages worked up i used 3/4 allthread across the bottom welding a coupler on both sides of the machine to screw into and a section of pipe that fit pretty good around the outside of the allthread......i welded my square tubing to the pipe for leavers and cut out some plate to make linkages im pretty happy with......wish i woulda took pics of them before i fished them under the pump for mounting (that was a pain but it can be done)

im talking to the guy i bought the pumps from and he says he has the cooler from his 743 so i think im gonna pick that up this weekend i figure he wants $100 for it and ill know its the correct size....i may also try to get the centering hardware if he has it but for now this is my first attemp at centering my levers.....they feel really loose and im afraid if i let them go the machine will run away from me

 

[619atv]

im talking to the guy i bought the pumps from and he says he has the cooler from his 743 so i think im gonna pick that up this weekend i figure he wants $100 for it and ill know its the correct size....i may also try to get the centering hardware if he has it but for now this is my first attemp at centering my levers.....they feel really loose and im afraid if i let them go the machine will run away from me

soryy this shoulda been pic for last post

 

[Tazza]

soryy this shoulda been pic for last post

Interesting centering setup you have there, looks like it may work ok.
If you can get eh centering gear from the other guy, it would help with holding it in place. The springs on your setup could change over time, making you battle for neutral.

 

[619atv]

Interesting centering setup you have there, looks like it may work ok.
If you can get eh centering gear from the other guy, it would help with holding it in place. The springs on your setup could change over time, making you battle for neutral.

Yeah tazza you are right the springs will wear out I'm sure so I added some washers and nuts to be able to adjust pretty easily......I think this will work for the time being.....does anyone have a pic of what the centering system looks like? All I have is a plate with two oblong slots in it but it looks like there should be a spring of Sie sort and I'm not really sure....I tried to pull up a schematic at a couple of different bobcat parts sites but with no luck........ Also how does the 743 lock out the hydraulics?....been racking my brain and I'm not sure how to do any solution I have thought of would cut hydro flow and cavitate my pumps....don't want that

 

[billrbg]

Yeah tazza you are right the springs will wear out I'm sure so I added some washers and nuts to be able to adjust pretty easily......I think this will work for the time being.....does anyone have a pic of what the centering system looks like? All I have is a plate with two oblong slots in it but it looks like there should be a spring of Sie sort and I'm not really sure....I tried to pull up a schematic at a couple of different bobcat parts sites but with no luck........ Also how does the 743 lock out the hydraulics?....been racking my brain and I'm not sure how to do any solution I have thought of would cut hydro flow and cavitate my pumps....don't want that

The stock system has closed-center directional valves that DO block flow, but the feed to them has a relief valve that bypasses them and the flow form that relief is combined with any return from those valves (when they are being operated to move something). All that good stuff is in that Block (Port Block?) that you don't have, and it ensures there is always flow through the cooler, filter, and for charge pressure.

 

[619atv]

The stock system has closed-center directional valves that DO block flow, but the feed to them has a relief valve that bypasses them and the flow form that relief is combined with any return from those valves (when they are being operated to move something). All that good stuff is in that Block (Port Block?) that you don't have, and it ensures there is always flow through the cooler, filter, and for charge pressure.

So that would lockout the bucket functions but with all that feeding the charge pressure the wheels would still be live wouldn't they? Just looking for a way to "dead" the levers when I get in or out of the machine....any ideas? What about an electric operated relief on either wheel motor system? This would create a weak point in the wheel system and wouldn't be able to create enuf pressure to move the wheels right?

 

[billrbg]

So that would lockout the bucket functions but with all that feeding the charge pressure the wheels would still be live wouldn't they? Just looking for a way to "dead" the levers when I get in or out of the machine....any ideas? What about an electric operated relief on either wheel motor system? This would create a weak point in the wheel system and wouldn't be able to create enuf pressure to move the wheels right?

Yes, the stock 743 will move if you bump the R/L wheel-drive levers, but I have never found it to be an issue. The levers have to be bumped a lot to get much movement. I'm not saying I have never bumped them (or hooked a shirt-sleeve on one), but it isn't a real problem.