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Can I flat-tow with full-hydro?? (Pic)

4K views 40 replies 18 participants last post by  jstarnes 
#1 · (Edited)
Can I flat-tow with full-hydro?? RESULTS!!!

The real question is, do I need to un-bolt the hydro ram from the tie-rod? Or, will leaving it attached damage the hydro system? I know linkage is not neccessary as it tracks & turns based on the castor angle of the axle. My only concern is damaging the hydro system. Nothing long-haul, just looking to get 30 miles to the local trails and back.

In case it makes any difference, I'm running an open-center, load reacting Danfoss steering unit w/ Howe aluminum TC pump

 
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#27 ·
with a single ended ram, it would work just the same as the system does with the truck running and steering wheel giving input. with a single ended ram one side has larger volume (like you described above), so what you end up getting is more turns for the side that has more volume. (example) so you would have like 3 turns to the right, and 5 turns to the left. i dont see how it would differ on a flat tow.
 
#28 ·
So, I got it hooked up tonight and tried 3 scenarios.

1. Truck turned off with ram attached and steering column unlocked. Turned easy to the left (which would be the cylinder's pressure stroke). But, was very difficult to turn back right and collapse the ram.

2. Started the truck and let idle while I turned both left and right. This time it turned left even easier, but it was still very tight trying to compress that cylinder back when turning right.

3. Disconnected the ram from the tie-rod and it worked perfectly. Tracked and turned awesome up to the 60mph I was able to do in my subdivision. Bolting it back up was only a matter of seconds. So, that's my story and I'm stickin' to it :D

Thanks for all your help!!!!
 
#29 ·
DougK20 said:
So, I got it hooked up tonight and tried 3 scenarios.

1. Truck turned off with ram attached and steering column unlocked. Turned easy to the left (which would be the cylinder's pressure stroke). But, was very difficult to turn back right and collapse the ram.

2. Started the truck and let idle while I turned both left and right. This time it turned left even easier, but it was still very tight trying to compress that cylinder back when turning right.

3. Disconnected the ram from the tie-rod and it worked perfectly. Tracked and turned awesome up to the 60mph I was able to do in my subdivision. Bolting it back up was only a matter of seconds. So, that's my story and I'm stickin' to it :D

Thanks for all your help!!!!
I am glad that you found out a simple enough solution. Too bad that there just wasn't quite enough force to get it to work for you with the ram connected. Be careful though towing with nothing to stabilize the steering, as when you least expect it, it might try to find a way to get ugly on you.

Sean
 
#30 · (Edited)
jstarnes said:
You care to post up a Hydraulic schematic of these valves you speak of?




or are you just gonna talk smack blindly with nothing to back you up?

the reason I ask is because the schematics I have seen say you COULD have a problem, and it MIGHT not track correctly due to the small amount of fluid that would have nowhere to go when the cylinder retracts which would lock up the cylinder which COULD blow the seals depending on what pressure the cylinder was built to handle

Granted in my scenario all the dots would have to connect for this to happen BUT it could happen

OK, so Dougs case shows that a reactive valve does indeed allow reaction with a single ended cylinder. The reason that the reaction was more stiff in one direction had nothing at all to do with any kind of hydro lock because of this being a differential volume cylinder. The only reason for the increased resistance in the one direction is because he was pushing against the bigger side of the piston in that direction , which means that at the pressure required to cause the geroter motor in the orbitrol valve to spin would take about 50% more force acting on the cylinder in that direction.

Thats the key to what you guys are not seeing with your claims of incompatability between load reaction and unbalanced cylinders. Regardless of whether you connect a balanced cylinder or an unbalanced cylinder to a load reactive orbitrol , when a great enough force is applied to the cylinder the gerotor is going to spin. When the geroter spins it opens up the working ports to the T port reguardless of whether the steering valve is in a neutral position or not(unlike the P port which requires input). When there is a positive or negative pressure between the working ports such as there is when running an unbalanced cylinder , this is compensated for by the opening to the T port.

The reason I wait this long to post this, and not post it with a diagram , is because I asked Danfoss engineers about this quite a while back, just to make sure that I was not doing anything without their reccomendation. They said , "NO PROBLEM" , and instead of answering all of my questions over the phone they answered them by sending me a Saur Danfoss technical bulletin that spoke specifically of this.

Well...... that was nearly 2 years ago, and I have moved in that time period. I can not find that technical bulletin with the diagram , so the other day I spoke with some Danfoss engineers again to see if they could send me that technical bulletin . They are very busy , and I have not heard back from them yet , but I am sure they will come though shortly.

Anyway... in the meantime I am being posted about in such a way as to be made to look an ass because of someones apparent personal grudge , and I can not wait for engineers in Denmark for "back up".

jstarnes said:
the schematics I have seen say you COULD have a problem, and it MIGHT not track correctly due to the small amount of fluid that would have nowhere to go when the cylinder retracts which would lock up the cylinder which COULD blow the seals depending on what pressure the cylinder was built to handle

Granted in my scenario all the dots would have to connect for this to happen BUT it could happen
Sorry but this is NOT a problem , a small ammount of fluid with nowhere to go ISN'T a reality , and it NEVER WILL cause you to "blow the seals" in a steering cylinder.

Sean
blind...
 
#31 · (Edited)
Station said:
OK, so Dougs case shows that a reactive valve does indeed allow reaction with a single ended cylinder. The reason that the reaction was more stiff in one direction had nothing at all to do with any kind of hydro lock because of this being a differential volume cylinder. The only reason for the increased resistance in the one direction is because he was pushing against the bigger side of the piston in that direction , which means that at the pressure required to cause the geroter motor in the orbitrol valve to spin would take about 50% more force acting on the cylinder in that direction.

Thats the key to what you guys are not seeing with your claims of incompatability between load reaction and unbalanced cylinders. Regardless of whether you connect a balanced cylinder or an unbalanced cylinder to a load reactive orbitrol , when a great enough force is applied to the cylinder the gerotor is going to spin. When the geroter spins it opens up the working ports to the T port reguardless of whether the steering valve is in a neutral position or not(unlike the P port which requires input). When there is a positive or negative pressure between the working ports such as there is when running an unbalanced cylinder , this is compensated for by the opening to the T port.

The reason I wait this long to post this, and not post it with a diagram , is because I asked Danfoss engineers about this quite a while back, just to make sure that I was not doing anything without their reccomendation. They said , "NO PROBLEM" , and instead of answering all of my questions over the phone they answered them by sending me a Saur Danfoss technical bulletin that spoke specifically of this.

Well...... that was nearly 2 years ago, and I have moved in that time period. I can not find that technical bulletin with the diagram , so the other day I spoke with some Danfoss engineers again to see if they could send me that technical bulletin . They are very busy , and I have not heard back from them yet , but I am sure they will come though shortly.

Anyway... in the meantime I am being posted about in such a way as to be made to look an ass because of someones apparent personal grudge , and I can not wait for engineers in Denmark for "back up".



Sorry but this is NOT a problem , a small ammount of fluid with nowhere to go ISN'T a reality , and it NEVER WILL cause you to "blow the seals" in a steering cylinder.

Sean
blind...

math doesnt lie

you can do the volume calcs of the cylinder piston and rod side and see that there different and since they tie together through the orbitol there could be a problem

and if the valve opened to tank it would pump all the oil in the cylinder back to tank (path of least resistance) what would then hold the steering from flopping arround (with exception to KPI, and castor)

the valve in the orbitol is OC so the P is open to T the valve opens when you crack the centering springs untill then the work ports are tied together through the gerotor (in the case of the reactive) nothing from the cylinder can make it to tank unless you compress the springs that center the valve and alow it to
 
#33 ·
jstarnes said:
math doesnt lie

you can do the volume calcs of the cylinder piston and rod side and see that there different and since they tie together through the orbitol there could be a problem
Absolutely , math does not lie , but it is things that you have said like this...

jstarnes said:
lock up is a bit harsh but I hope every one understands what I mean


which is that once the steering moves so far in one direction it will stop because a "single ended cylinder" has 2 sides to it one side will always have more volume area than the other the lesser side will pump oil into the greater side ok but the greater side will only pump the amount of oil it takes to fill the lesser side then it will stop with X amount of oil left over with nowhere to go
... that make me think that you are missing some numbers.
I know that neither I nor physics know what you mean here... Please explain to me how a differential displacement cylinder , filled with fluid, and with the ports plumbed straight to one another ( As you say is the case in the orbitrol) would be any other thing than locked up? It would be hydrolocked and you would not be able to move it even the first 1/8" in either direction . How could the cylinder possibly work " ok " in one direction? In a closed enviroment the vacuum created by a larger volume trying to draw from a smaller volume would create an instant vacuum that would be just as powerful in keeping the cylinder from moving as the pressure created in the opposite load direction.

jstarnes said:
and if the valve opened to tank it would pump all the oil in the cylinder back to tank (path of least resistance) what would then hold the steering from flopping arround (with exception to KPI, and castor)
Dude.....come on , you need to cool your head down a bit before your next retort, because I know you are smarter than this. You don't think that the suction caused by the extending side of the cylinder would be the path of least resistance?

jstarnes said:
the valve in the orbitol is OC so the P is open to T the valve opens when you crack the centering springs untill then the work ports are tied together through the gerotor (in the case of the reactive) nothing from the cylinder can make it to tank unless you compress the springs that center the valve and alow it to
We have already had a first hand account by someone impartial to our disagreement here give us an account of the steering cylinder being able to travel through it's stroke with the orbitrol valve in a neutral condtion. You should already know that you are wrong; you don't know why , but yet you insist on arguing.

Obviously nothing I could say would go anywhere with you, so mentioning to you that I have only done about ~70 rigs this way without issue , and that before doing any customers rigs I conducted some of my own tests to see what happens. The result was that I was able to extend and retract and extend the cylinder by hand pushing on the tires off the ground, but that wouldn't mean anything to you.

I have told you that I have spoken to Danfoss engineers myself , apparently you don't believe me.

You and the competition can believe that this does not work all you want to , but I won't be the blind one.

Sean
 
#35 ·
Tim84K10 said:
I'm still wondering if what I'm seeing is a Chevy with a stock tie rod, and a ram mounted in single shear on the stock steering stabilizer mounts. That's a pretty shaky way to mount it IMO.
Good observation... Though, the tie-rod has since been sleeved in angle-iron and the 3/4" grade 8 single sheer works great for the moderate trails my rig can handle. I'll be able to justify a nicer tie-rod setup (double-ended ram!) once I upgrade to a Dana 60. The ram axle tube mount design was changed and strengthened as well.

Thanks for the replies about my towing query! No other forum even had a clue :shaking:
 
#36 ·
DougK20 said:
Good observation... Though, the tie-rod has since been sleeved in angle-iron and the 3/4" grade 8 single sheer works great for the moderate trails my rig can handle. I'll be able to justify a nicer tie-rod setup (double-ended ram!) once I upgrade to a Dana 60. The ram axle tube mount design was changed and strengthened as well.

Thanks for the replies about my towing query! No other forum even had a clue :shaking:

Sorry you had to wade through all the BS. When you are ready to go the next step with that hydro steer setup , please give me a call, as Howe is not the only option. Going to a double ended ram probably does not cost as much as you think(Used to Howe prices).

Sean
 
#41 · (Edited)
Station said:
Please explain to me how a differential displacement cylinder , filled with fluid, and with the ports plumbed straight to one another ( As you say is the case in the orbitrol) would be any other thing than locked up? It would be hydrolocked and you would not be able to move it even the first 1/8" in either direction . How could the cylinder possibly work " ok " in one direction? In a closed enviroment the vacuum created by a larger volume trying to draw from a smaller volume would create an instant vacuum that would be just as powerful in keeping the cylinder from moving as the pressure created in the opposite load direction.





Sean

Lets look at this cylinder http://www.surpluscenter.com/item.asp?UID=2005073009524511&item=9-5100-05&catname=hydraulic

The bore times the stroke = swept the volume of each side

So 7.06 X 5= 35.3 for the piston side

And 7.06 X 5 -1.2 X 5= 29.3 for the rod side

IF the piston is at mid stroke of the cylinder you would have 17.65ci of oil on the piston side and 14.65ci of oil on the rod side (total of both sides = 32.3ci)

For every inch you stroke the cylinder rod out you increase the volume of the piston side by 7.06ci and you decrease the volume of the rod side by 5.86ci

So from mid stroke you can connect both work ports with one hose, and lets say your perfect and can do it without loosing any fluid volume from the cylinder or hose you would then be able to pull the rod out (remember were talking about external forces acting on the steering system) swapping all the fluid from the rod side (14.65ci at mid stroke) into the area created by the piston moving in the barrel (remember at full stroke rod out you have 35.3ci volume on the piston side) so you would be pushing 14.65ci of oil into a space that has just been opened up by 17.65ci (7.06ci/inch of travel)leaving a vacuum area of 2ci (remember the cylinder was sealed that means no air in or out, if there is a force strong enough to cavitate the cylinder it will if the force is not high enough to pull vacuum the cylinder would stop moving once the 14.65ci of oil was transferred)


So you just took the single ended cylinder from mid stroke to full rod extend out now you have 32.3ci volume of oil on the piston side of the cylinder and a 2ci vacuum pocket NOW you want to push the rod in to swap fluid (the 32.3ci you have on the piston side is the total fluid you have remember the cylinder is tied together with one hose and the volume of the hose is irrelevant) from the piston side to the rod side

So we already know For every inch you stroke the cylinder rod out you increase the volume of the piston side by 7.06ci and you decrease the volume of the rod side by 5.86ci
Lets take the reverse now your pumping 7.06ci oil every inch of stroke from the piston side into a spot being created by 5.86ci/inch so math tells us the cylinder will stroke IN by 1.2 inches before the volume of fluid being pumped becomes to large for the area its being pumped into

That scenario was tossing out the area of vacuum that might be created ( I will be honest and say this theoretical vacuum pocket is the only area of this that Im sketchy on, and only on how it would affect the amount of rod movement)
 
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