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Help operating a Hydro-Ax 670

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
New project came up today. I know nothing about this type machine other than what it does, or is supposed to do. Being the brave (fool) I am, I hop up into the cab, and to my surprise, it starts right up. So now what? I see a left and right joystick, each with a toggle switch on top and a trigger button on front. On the floor I see on the far right a sort of split pedal. More or less in the middle I see what I assume to be a brake. So I start moving levers and switching switches. I figure out how to open and close the claws, I found the switch that activates the solenoid for the blade motor. I can raise/lower/tilt the operating head. What I can't seem to do is make the machine move forward or reverse. I am thinking that the split pedal on the right is for that. I find no throttle anywhere.

I don't know what model year this is yet. Have not opened the covers to look for any ID tags. I was told that one of the guys found some control cable mechanism had lost a bolt....no idea where, control of what, or anything more than that. Naturally, no paperwork/manuals available in house. On the surface, it seems to either lack a throttle to increase engine speed to engage a hydrostatic drive and move, or there is an unknown and unidentified control somewhere I have not located. Granted, I only spent 15 minutes with it today, but I am asked to get it figured out asap, as there is a job waiting.

Anyone familiar with this piece of machinery? A quick tutorial about how to drive it around? I'm not going to be the operator, I just need to know how to drive it.

oh, and this isn't one with the shredding head. It has a circular saw that cuts the tree while grasping it, then lays it down. AKA Feller-Buncher, I believe.
 
Last edited:

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
For anyone in the future, I'll fill out what I can on this machine. It is tagged a Blount Model 670. It is designed to operate at a fixed engine speed, with that controlled by one of a series of rocker switches on a panel to the right of the operator's seat. This particular machine is not labelled(yet), so it took some experimenting to find. The throttle control is a push-and-hold to change from an idle up to speed, as indicated on the tach, with a green band marking the proper speed for cutting. Same rocker, pushed and held the other way idles the machine back.
The split pedal I referred to is indeed a F-R control. With the parking brake released, and the throttle up a bit, the transmission engages in either forward or reverse. I was able to drive the machine around the yard, forward and reverse, so it's not a dead one. BUT! The problem at hand is apparently centered on the Hi-Lo selector lever, which is located very low on the right side of the cab. There is an aluminum housing with a rubber dust boot protecting a single rod with a knob on it. It seems that it should have a H-N-L, but at this point, moving the lever has no feel of making any shift in the transmission or moving in any positive steps, or detents. I believe it simply operates a pair of sheathed cables that lead back to a shaft at the transmission that has a double ended lever clamped to that shaft, giving a rotary action to that shaft. Thus the Hi-Lo or Hi-N-Lo valving is likely internal. At this point, the machine appears ti be in high gear and that, I understand, is only used for transport. Ideally, I can find the source of binding or some problem with the cables, if that's what it is, and clear it up. I only hope there is no problem with low gear that the PO found and somehow rigged the machine to run in high only to get rid of it. If it comes down to it, for now I think I can live with low only. The job it's assigned to is far enough away that it will be trailered in, and right now the focus is on about 5 acres of a larger plot, so it won't need to move too far, too fast.

If I don't get rained out, or I can manage to clear some space in one of the buildings, I'll jack the cab over so I can see just exactly how that shifter is supposed to work and why it isn't. I'll post a pic or two of the cab and controls. That is mostly just to help build this repository of information.
IMG_1249.JPG IMG_1251.JPG
 

old-iron-habit

Senior Member
Joined
Nov 22, 2012
Messages
4,233
Location
Moose Lake, MN
Occupation
Retired Cons't. Supt./Hospitals
I have a smaller version. A 411B. Mine is electric shift on the two speed. A simple toggle. They are not speedsters by any means. High will not be over 5 MPH. A fast walk at best. Low is half that. For cutting you drive thru the tree. Last time I visited the site ten years ago you could still download all the PDF Hydro Ax manuals at Road Machinery and Supply's website.

EDIT: Did you try pulling up on that knob? If my antique partial working brain remembers right some of them had a knob to lift to shift the drive.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
Hmm, no I didn't try pulling it. It does seem like it should have some sort of mechanism to keep it in whatever gear you put it in, a lock of some sort. I'll give that a go in the morning. It just seems, well hard to describe, but mushy?...acts like it isn't really moving anything. Of course you can't see anything on the transmission while the cab is down to know if it's even trying to move that shift lever. Can't reach the lever from where you can see, so I'll have to get some help for another pair of eyes.

Thanks for that site info. I'll check and see if they still have anything.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
It appears that the cast aluminum (or Zinc alloy) housing that has the pivot for the hi-lo lever is missing some fasteners and at the exit point for the cable. Attached to the lever there is a clamp of sorts (again missing screws) that grabs a preformed collar on the cable housing. Due to the missing fasteners, the cable housing has slipped out of place and nothing is holding it. The cable is free to move in the housing, allaying some fears of a rusted, frozen up cable. All the pieces seem to be there, just not secure in their proper positions. I rounded up all the appropriate fasteners and will put it back together. Perhaps with one improvement. The pivot hole in the lever has what I believe are Delrin (HDPE) bushings, so obviously the fastener used there would have a smooth shank above the threads that provides a bearing surface of sorts. I am substituting a socket shoulder screw (aka stripper bolt, for the Tool and Die guys among us).It is precision ground and a good fit in those Delrin bushings. A Stover lock nut on the other side and it should last the life of the machine. So much for the shift control housing.

On the other end of that cable there is a lever arm pinned to a shaft coming out of a gearbox. There is a fair amount of wear between the lever arm, which is welded to a round boss bord to fit the control shaft. In fact, it's quite sloppy. Major job to pull all that apart and make a new control shaft, or turn the old one true and sleeve the boss to fit it, so I intend to try and run the machine with it loose. I can shift from one position to the other (Hi and Lo) with the cab end of the cable unhooked from everything, so I believe once I have reassembled the control cable/lever housing in the cab, things should be ok. Worn a bit, but ok. If not for a hot job for this machine, perhaps I would (and probably will at some point) address the sloppy fit properly. I hate it, but it's a "get by for now" repair. Sometimes just gotta do that.

I only hope there has not been any clutch damage from running in high gear all the time. This is an auction machine, so I can't say how long it's been running like this.

If anyone is reading this, I could use some help finding a manual on it. The owner of this group of machines has instituted a (good) policy of getting books on everything we have when we work on it. Eventually, that will be a room full of manuals. I read some of the history of Hydro-Ax, and can't say for sure who even owns or builds them these days. My specimen has a Blount ID tag, but from reading, that may not mean a lot. Any suggestions would be appreciated.
 

daveyclimber

Well-Known Member
Joined
Aug 3, 2017
Messages
59
Location
Cottonwood, CA
You will only need to operate the machine in low gear. High gear is for road travel basically. High gear top speed is about 15mph, too fast to keep up with steering. There should be a rocker switch that will electronically select lower and higher hydraulic flows to act as a low gear two speed. The cable operated selector does indeed have a low neutral and high. Handle up is high handle low is low. I run a Prentice 2670 as a mulcher, it is almost exactly the same machine. I have all the manuals, about $500 worth. If you need specific info I may be able to help.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
The latest on the machine is that I had the shop guys pull the trans, since it got in a bind and would nor shift into high at all, and low seemed to really be neutral, no drive at all. Shifter fork was bound up and bent some. I straightened it, worked it into low range, and with the guide rod protruding out of the case, I put a clamptite collar on it to prevent it from moving back into the case, and allowing it to slip out of low range. I had already removed the control cable and shifter box to keep the operator from messing with it. When there is time (ha!), I'll probably go back and replace that cable and see if I can free up the fork or collar on that idler gear. But for now, I definitely agree. Low speed is all we need. On and off the trailer, and from tree to tree. I have it at my personal shop now, but will deliver it back to the guys to install it tomorrow. It took less than a day to remove it, probably a bit longer to reinstall it. But it appears to be locked in low,which is what we wanted for functionality.

Oh, and I did at least find an owner/operator manual for it. I've heard Service manuals are virtually nonexistent. I think we may be good to go though, and will find out tomorrow or Friday.

The rockers aren't labelled very well on this old machine. I don't see anything that looks like it might have the function you describe. Could you post a pic of the page in the book that has the switch functions identified? That would help a great deal. I can make some labels for mine.

Many thanks, daveyclimber
 

daveyclimber

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Joined
Aug 3, 2017
Messages
59
Location
Cottonwood, CA
Here are how my switches are laid out. Starting from the top. Hour meter, 2 switch blanks, hvac temp control, 3 switches from left to right. AC/Heater, rear diff lock, blank. Next 3 switches, hvac fan speed switch, hi/low travel speed switch, work lights. Next 3 switches, engine speed control, blank, blank. Last 3 switches, horn, blank, hydraulic override switch. Not exactly sure what that does but it will allow me to travel with the door open and steer with the parking brake on. One the dash I have 2 switches. Left controls the hydraulic reversible fan and the right controls the saw or attachment pump. I have some spare parts I'd be willing to part with as I have no us for them . Left and right hose guards which mount down at the center joint. They are for the power unit side. New lower attachment pins for the loader arms, control computer, wiring and valves for the reversible fan. Let me know.
 

old-iron-habit

Senior Member
Joined
Nov 22, 2012
Messages
4,233
Location
Moose Lake, MN
Occupation
Retired Cons't. Supt./Hospitals
You will only need to operate the machine in low gear. High gear is for road travel basically. High gear top speed is about 15mph, too fast to keep up with steering. There should be a rocker switch that will electronically select lower and higher hydraulic flows to act as a low gear two speed. The cable operated selector does indeed have a low neutral and high. Handle up is high handle low is low. I run a Prentice 2670 as a mulcher, it is almost exactly the same machine. I have all the manuals, about $500 worth. If you need specific info I may be able to help.



Blount (is or was, not sure if they sold) owns both Hydro AX and Prentice as well as a bunch of other logging equipment manufacturers. RMS has been a distributor for many years.
 

daveyclimber

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Aug 3, 2017
Messages
59
Location
Cottonwood, CA
Cat Forestry was the latest owner but Cat gave up on the forestry market from what I hear and sold the whole forestry division along with Prentice and progress rail I believe to Weiler who makes asphalt pavers. Oh and the black button on the right hand joystick will operate the front axle locker when depressed, it is momentary.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
Looks like I have some wiring to do then.

And now, with the trans back in, I get a phone call that says the machine won't move at all. Guess I know where I'll be in the morning.

Sounds like parts are going to be hard to find now. Great.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
Ok well the guys were correct. The machine won't move. It lurches a little if the propel pedal is held about halfway down, but that's it. No forward and no reverse movement. So I made up a test gauge so tomorrow I will see what the pump is putting out. Book says max is 5420 psi, so we'll see. I'm not sure I'm understanding the layout/plumbing of this machine. The propel pedals are where in the system? It's a hydrostatic drive, so the pump is a variable displacement I suppose, but how do the pedals control the swash plate? I wish the owner manual had more detail. I'm betting the pump is running low pressure and I'll have to rebuild it. The other pumps seem fine. Everything else moves or spins like it should. And I am presuming the default position of the solenoid on the back end of the hydraulic motor is "low" speed. The coil is not open, but I don't have the resistance spec for it. I believe it's around 3.7Ω across the coil. That figures out to be a bit over 3 amps, so not a short or over-current situation. Whether this solenoid is functioning properly or not I can't tell, but I don't believe it could stop the machine from moving.
 

daveyclimber

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Joined
Aug 3, 2017
Messages
59
Location
Cottonwood, CA
Parts are still readily available for these machines. Do lifting and steering functions work? My machine has safety interlocks and wont propel if the door is open( switch at lower rear corner of door jamb) parking brake engaged or switch fault. You mentioned an issue with the transfer case shifter. Is it stuck in neutral?
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
Daveyclimber, just about all of the interlocks have been butchered off of this machine with the exception of the parking brake, which is not even connected to the brake system. The brake lever must be in its disengaged position for anything to work, so the switch is still in circuit, but there are no brakes. Steering, clamps, saw, all of that works normally....and yes, with the doors open. Someone has spent a lot of time taking things off this machine. The hydraulics test point panel? Nothing is connected. Nothing. The manual shifter for the transfer case/gearbox had a faulty cable, and the decision was made to put the machine in low range and lock it there with a clamptite type locking collar. So no, it's not in neutral. It's definitely in low.
 

daveyclimber

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Joined
Aug 3, 2017
Messages
59
Location
Cottonwood, CA
PM me your phone number if you like. I will text you a picture of the propel troubleshooting info out of my service manual. Not sure how to post pics here.
 

partsandservice

Senior Member
Joined
Feb 14, 2011
Messages
846
Location
Georgia
There might be a rag or blue cap in one of the propel hoses. Another one of those ask me how I know things. Simply removing the motor from the drive system and now it only lurches there is likely a blockage in the loop or containation.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
Well, P&S, it was doing the lurching before, from the beginning. If you ran the engine speed up, and hit the forward propel pedal, in about 5 seconds it would sort of jump forward a few inches, then a few more, and repeat this until it was actually moving, albeit sort of rough. It was definitely in high range though. I was able to drive it around the yard, stopping and starting, and once it was at full temp it seemed to fully engage and take off more normally. Once it cooled down though, it was a repeat of the jerking and lurching. I could see it being a problem with line blockage or something like that. Once the oil thinned out, it seemed to do a little better.
 

partsandservice

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Feb 14, 2011
Messages
846
Location
Georgia
Was not aware of existing condition. Daveyclimber, to post pictures if you so desire, just click upload file and select picture. Then choose thumbnail or full image and click post reply.
 

Tony Wells

Senior Member
Joined
Jul 18, 2019
Messages
635
Location
Tyler, TX
Occupation
HogZilla Keeper
Today, a limited bit of testing took place. It's difficult to do the recommended tests when most all of the ports are inaccessible, and the bulkhead where all the test points are hosed to has been stripped of all connecting hoses. Really aggravating. If I has the time, I'd hose all of them back up so that in the future the next shmuck would at least be able to throw some gauges on without being a contortionist or knocking the cab over time after time, ad nauseum.

Anyway, as far as what got done today, working with an old CAT hand who's pretty sharp, we tested the pressure from the propel pump. The way we did this was done not so much by the book, but by instinct and book combined. There are three lines from the propel pump and the propel motor; Forward, Reverse, and Case Drain. Step one; d/c and cap off Reverse port at pump. Step two: Connect 10kpsi pressure gauge to Forward port at pump. Step three: Remove Case Drain from Propel motor and connect service hose to catch pan. ( this is where I start questioning our procedure. I have no idea what is supposed to come out of the Case Drain port of the motor; I'm thinking not a lot. It's normally routed back to the reservoir, but I don't know. Especially with all the custom hosing on this machine.)

So, essentially I have dead-headed the propel pump into a 10,000 pound gauge for this test. Cab is lowered, mechanic in the cab. Cranks normally, for this suicide machine, and I read about 600 psi at low idle. A quick touch of the propel pedal drops it to virtually zero. No working tach, so just guessing on these speeds. We bump the speed control up to its naxt notch, I'm guessing around 1500-1550. Pressure hops lively to around 1k. Run the speed on up, and the pressure follows. Now we go for it. Engine speed up to normal op speed (really need to fix that tach!) Pressure hops on up to around 3200 psi. Then the op hit the propel pedal lightly, the pressure went on up rapidly to about 5400 psi. I'm taking this to mean that the propel pump itself (base pump) is fine, capable of producing proper pressure. I don't have a flowmeter, and with it deadheaded into a gauge that would be pointless anyway. Maybe later I'll add one to the kit, and can check things while they are running. I also believe the pilot system is functioning properly, as the idle pressure is low, as it should be, but with throttle up, it jumps right up to proper pressure to run the propel motor. Since I got the readings I did, I decided not to test for the same pressures from the reverse side. The drive problem seems identical whether it's in Forward or Reverse, so I didn't see the point. This test also indicates to me that the circuit that includes the pedals is ok as well, since the system responded in the way it did: drive pressure jumped up immediately to where the machine ought to be trying to move.

So, the next question is about the motor itself. It's a variable displacement swashplate design, and I question exactly what controls the angle of the swashplate in order to keep it where it should be on the speed/torque curve, and what sort of problems are possibly or likely to cause a failure of the type I see here (no move). Since the normal test lines have been removed (but can be put back, easily, at a minimum what ports on the transmission should I be looking at? And how much oil should be lost through the Case Drain? Or does the fact that I have ample drive pressure indicate there is some obvious (though not to me) problem that will need to be addressed through a teardown. It's not a difficult R&R, but the guys obviously won't be happy since they just had it out to pull the gearbox for me. Or since I am short on time, should I just buy another propel motor?

You guys are more help than you probably realize, and I can't express well enough my appreciation for your assistance.
 
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