Hawk-Bilt Ground Saw

[Paulf]

I've been working on it since November, but finally got my groundsaw all rebuilt. Everything works on it, but it's been too muddy or the grounds been frozen so I can't try it out. Everything works, but I haven't been able to do any digging with it yet. I'm anxious for some warmer, dryer weather to try it out and do some painting.

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I kept a pretty good record of the rebuilding process as I went along. It has so much detail that you'd probably only be interested if you're rebuilding a ground saw but if you're interested you can read about it here:

http://www.cubcadetman.com/content/inde ... ut=default

It was one of the neatest projects I've worked on and really enjoyed the challenge of getting it going.

[vince_o]

Wow Paul what work!

How do you think that berring will hold up in the dirt, not that your going to run water lines with it every day, and how many hours do you think you have in this.

[Paulf]

Vince, that was the same type of bearing and support that was in it originaly and by the wear on some of the parts, I'd say the bearings held up really well. As far as invested hours, let's just say I'm glad I'm retired!! On the other hand, everything on the project just seemed to work out. It seemed like every thing came apart and went back together without a hitch.

[bbaker]

kewl project Professor! I know who to come too next time I need to bury a water line!

[mic]

paul, rebuild looks fantastic ! bet you can't wait to try it out! good to see an old piece of equipment come back to life !
Great Job!!!

[Paulf]

Bryan, I don't know about digging a ditch for you, but if you get hung up in one, give me a call. If I can get this thing all figured out, I'll give you a pull!!!

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[ljones]

Paul f, did you buy that original 4x4 project from Rick Beem? If so glad to see you got it.

[bbaker]

Bryan, I don't know about digging a ditch for you, but if you get hung up in one, give me a call. If I can get this thing all figured out, I'll give you a pull!!!

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I would think a retired engineering professor can figure that out! Especially with some of the tools you have or have access too!

[Paulf]

Lucas, yes it belonged to Rick. I picked it up from him a month or so ago. He had lengthed the frame by about 6 1/2 inches and had planned to put a Teledyne in it. I put the winch on the front to "hide" the increased length. I'm toying with returning it to the original length and do away with the winch. I really don't care for the longer look of it. I'd be interested in everyone's opinion. I personally think the longer look gets it too much away from an Original.

Bryan, I'm now working on Plan C!!! The output of the rear PTO has to be speeded up and reversed to drive the front axle. With the limited space available, I keep having to change how I want to do it. I am getting closer though. Our buddy, Chuck, has been a really big help.

[J Hayes]

Paul I'd say with the extra length especially if your only going to use the saw with it , would be better to leave it alone. I'd think the extra length would help in the balance when ***** is out of the ground , and when it is ... maybe make it a bit more stable if your into small rocks. ... Just my 2¢ better make that 3¢ (Inflation)

[DaveKamp]

Okay, so... how about driving a small fixed-displacement hydraulic pump off of the pinion, and plumbing it to a hydraulic motor on the front axle...

That way, your transmission and PTO speed are irrelevant? Hydraulic FWA...

[jspicer]

Paul,
The ground saw looks great. I remember when you got that thing. I'd love to see it in action .

Jim,
I think he's talking about shortening up the length of the frame in the 4X4 Original. Wondered where that O ended up. Congrats Paul.

[bbaker]

Okay, so... how about driving a small fixed-displacement hydraulic pump off of the pinion, and plumbing it to a hydraulic motor on the front axle...

That way, your transmission and PTO speed are irrelevant? Hydraulic FWA...

like the combines have? How would you get the speeds to match?

[Paulf]

I've been off line to attend the National Farm Show in Louisville, KY. It's an amazing event if you've never been there.

Dave, I'll call that Plan D. I don't want to start an argument of hydro vs. gear drive here, but I don't like to use hydraulics because of the power loss even though they are a lot easier and simplier to work with. If I use a hydraulic pump and motor as you suggest, I guess I could either use a chain drive to increase the speed of the pump to get the increased speed to the front motor or "find" a hydraulic pump that has 3.3 times the capacity of the motor. 3.3 is how many times I have to increase the output of the rear PTO to get the 2% overdrive I want for the front.

By the way, Plan B is to use a chain drive at the front and rear to get the speed change I need and connect the two with a "sliding" PTO shaft. To get the needed "reversal" I'd install the engine rotated 180 degrees. That would make the output of the rear PTO the correct direction for the front input. To get the rear end turning in the correct direction, I'd have to flip the rear ring gear and carrier? (Clear as mud???) Unlike the rear end of a Cub Cadet, the front drive is not symmetrical so it can't be flipped.

Thanks for any and all suggestions, everyone. It's appreciated.

[ljones]

Paul, if I had it I would definitely shorten the frame back to stock, it makes it look weird

[DaveKamp]

Hmmm... perhaps I didn't make the concept clear enough...

Don't use the PTO to drive the front axle... if you do, you'll lose the ability to use the transmission to select your ground ratio.

Instead, install a hydraulic pump inside the transaxle, and drive the hydraulic pump off the PINION SHAFT... the one that drives the ring gear. Or if you're really clever, take the back cover off the rearend, and fabricate a new one that's really beefy... mount some bearings and another CUB pinion shaft in it, and drive the hydraulic pump OFF OF the ring gear, using the second pinion.

This way, whenever the rear axle turns, the pump moves hydraulic fluid in direct proportion to forward motion.

Now, take that fluid, and plumb it up to a hydraulic motor on the front axle.

This is NOT a hydrostatic drive, it's a hydraulic fluid power system. The drivetrain losses suggested with a hydrostatic pump are not present here, because there is no hydrostatic pump- it's a fixed displacement pump, moving fluid at a proportionate rate to rear drive rotation. From there, you're just using the rear axle to drive the front axle, and the only losses (beyond friction) is whatever you incur as a result of having restrictive plumbing... and you solve that... simply by not having restrictive plumbing.

Making the ratios match isn't rocket science... you've determined a 3.3 drive ratio with respect to something... from what I'm reading, it appears you're getting it from the PTO shaft, in which case, one has to assume that the manual transmission is in some particular gear. Throw all those predispositions away- you want four wheel drive REGARDLESS of what gear you're in. To accomplish that, you'll need to take off your power from some point DOWNSTREAM of the transmission. This is why I suggested placing a fixed-displacement hydraulic pump on the pinion shaft. IN retrospect, I can't believe I overlooked the whimsical simplicity of just putting a hydraulic pump on a pinion gear that meshes onto the existing ring gear... by doing so, one could put hydraulic FWA on ANY cub cadet, simply by yanking the rear cover, installing a new rear cover that has appropriate bearings, a pinion gear, shaft and mounting face for hydraulic pump (an SAE-A pattern would do nicely), then you're just talking about two hoses, and a hydraulic motor on the front axle. The ratio will merely be a function of determining how much flow volume is required at the back (drive) end in order to result in the appropriate amount of flow at the front end.

And finally, when you're in a situation where you need to disengage the front drive, or give it some compliance for tight-quarters maneuvering, install a valve between the two hoses going to the hydraulic motor... this will bypass flow, effectively allowing the front axle to 'freewheel' while the valve is open, and then 'lock' when the valve is closed.

[DaveKamp]

Okay, so... how about driving a small fixed-displacement hydraulic pump off of the pinion, and plumbing it to a hydraulic motor on the front axle...

That way, your transmission and PTO speed are irrelevant? Hydraulic FWA...

like the combines have? How would you get the speeds to match?

Getting speed to match is just a simple matter of ratios.

Let's say that the front wheels are half the circumference of the rear, and have a 3.73 gear ratio.
Let's say that the rear wheels are twice the circumference of the front, and also has a 3.73 gear ratio.

This means that the front pinion must make TWO rotations for every ONE rotation of the rear.

Install a 2 cubic inch per rotation pump on the rear pinion, and a 1 cubic inch per rotation hydraulic motor to the front pinion.

Now, the rolling distances will match... AND... the front and rear axles will ALWAYS be driven.

Let's say he wants the front wheels to be driven SLIGHTLY FASTER in terms of ground speed... make the rear a 2.20ci/rev pump, and drive a 1ci/rotation motor.

[Paulf]

Dave, sorry I didn't make myself clearer. The rear PTO that Rick installed drives directly off the pinion shaft. So, I already have a rear PTO that's independent of what gear the transmission is in. And, I have determined by gear ratios and circumferences that the rear PTO has to rotate 3.3 times faster to drive the pinion shaft on the front axle at 2% overdrive. Sorry I wasn't clear, but the PTO shaft I mentioned wouldn't be part of Plan D. Plan D would only involve a pump, motor and hydraulic hoses if I could find the right combination of displacements for a pump and motor. Again, sorry I wasn't clear about that. But, if I couldn't find the correct combination of pump and motor that would mean if I had a rear hydraulic pump and front hydraulic motor that were an exact match in displacement, I'd have to use a chain drive to speed up the rear pump by 3.3 times or a chain drive from the front motor to the front pinion shaft that would speed it up 3.3 times (or some other combination of displacements and speeding up both or either so that everything works out to 3.3). That would seem easier to me then finding a pump that has exactly 3.3 times the displacement of a motor, but I haven't investigated that possibility. Surprisingly, a small change in that 3.3 makes a large change in the percent overdrive.

And, again, not to create a gear drive vs. hydrostatic drive debate, but my groundsaw has only a hydraulic pump and motor but has to have an oil cooler and fan--no hydrostat involved. The oil cooler and fan are required because the hydraulics (again, no hydrostatic drive involved) creates heat. Heat equates to energy loss. I don't have that problem with gears since they're like 98% efficient. The oil cooler I used on the groundsaw came from a Model 155 Case which was driven by a hydraulic pump driving a hydraulic motor--not considered a hydrostatic drive. The combination of pump and motor creates heat which results in energy loss. I don't have that problem with a gear drive. I agree that hydraulic drives (hydrostat or otherwise) are a lot simplier then gear drives but you pay the price in energy loss. And, to be perfectly honest, I like the challenge of figuring out the 4 X 4 without hydraulics. It's a lot more satisfying if I can figure it out.

Lucas, I agree. "Wierd" is a good choice of words. But you'd be surprised how many of my friends like the looks of the extended length. I'm still debating.

[NHIRONWORKS]

Hey Paul,
I read the Ground Saw "Does not need a winter vacation" and will cut through frozen ground! It's on the sales brochure, give it a go!

[DaveKamp]

Okay, well, if he's got it set to drive straight off the pinion, then you're in good terms to start with ANY type of driveline, because you'll be able to use your gear selection without having any complexity afterward.

You're correct that the groundsaw has a cooler, and the cooler results in loss. The hydraulic pump SHOULD be driven off the engine coupling (Eric's isn't, BTW, but every other Groundsaw I've transported did)... which means it's turning at governed speed, and since that pump is doing EVERYTHING (running the saw chain, lifting the boom, and propelling the machine forward via the hydraulic motor driving the PTO shaft), AND since you can bury the blade hard enough to kill the engine (Noel does this frequently) you can safely assume that the pump, under normal conditions, is not only capable of absorbing 100% of the prime mover's power, it's doing it at a high rate of duty... like... probably 80% or more... at high velocity through the plumbing.

Let's compare this to PTO output between the front and rear of the FWA as I noted. When you propel forward, the hydraulic pump located on the PTO shaft is turning at a given rate commensurate with R&P gear ratio.

Let's say you're using a: http://www.surpluscenter.com/item.asp?i ... =hydraulic that has a displacement of 2.5ci per rotation.

And couple it to: http://www.surpluscenter.com/item.asp?i ... =hydraulic at 3.4 ci per rotation, for a net change of 1.36 overdrive. In order to hit the magic ratio, you'll need a

To get an appropriate volumetric match, you'd need a 0.41 overdrive, or a 1 : 2.43 ratio (pinion to pump). This means 14 * 34 on a #40 chain would do it, and the sprocket sizes would be realistically capable of fitting AND transmitting the power.

Back to loss:

When the groundsaw is running, the pump is providing power to the saw motor, AND flowing through the valve stack to run the boom on demand, AND drive the wheels, again on demand, but moving at a consistent rate usually. This means system IS carrying pressure. IF you put a pressure gauge on the system and observe input pressure, you'll see that pump line pressure is very low until such time that the saw is placed in the ground. Why? Because it's an open-center system. With valves released, fluid being pumped by the engine is returned to tank, with essentially no restriction. The only 'waste' heat being generated, is by pump friction, and that which is flowing through the hoses. In this respect, if you start the groundsaw on a -20F day, open the throttle, and just let it sit, the ONLY heating that will occur in the system, is from restriction in the hoses, and friction in the pump's whirling gears. It will NOT be enough to ask for the heat exchanger.

Now, if you idle it down... you will likely not see more than a few degrees' rise in temperature... if you can see it at all. Slow flow rate, through ample plumbing, and very little friction in the pump at that speed... the only thing absorbing ANY energy, is the viscosity of the oil.

Now set the blade in the dirt, and your pressure gauge will shoot up... and the engine will grunt... because the pressure in the system (Regardless of engine speed) is a function of resistance at the FAR end... the load being applied to the hydraulic motor. Once the hydraulic motor is feeling resistance, pressure in the lines will climb, the engine will work harder... and you may even 'peak' it every so often and cause the pressure relief valve (in the valve stack) to crack open for a smidgen, dumping a little pressure back to the tank... but if you try hard, you'll just stall the engine.

Now compare this to the driveline duty:
Rolling across the yard, rear wheels turning, front wheels turning... all ratios mathematically appropriate... the pump is moving a given amount of fluid through the lines to the motor, which is, by virtue of the ground moving beneath the wheels, is already turning at an appropriate velocity for the incoming fluid... hence, the PRESSURE in those lines is effectively zero. It is also, by the way, moving very slowly. Rather than the pump being whirl'd at 3600, it's turning a few dozen rpm at most. Same goes for the hydraulic motor... an order-of-magnitude less than it's design limits, so heating from friction is nada. That hydraulic motor might as well be considered HELPING the pump... the only power loss is what's required to pump a wee bit of fluid through substantially larger lines than necessary... so no heating.

Now, let's say you bury the back end... gas it good to dig out, and the front wheels grab something solid... now you have the rearend spinning free, but the pump is driving the front wheels, which drag you out of the hole. For that 6 seconds, the frontend is carrying most, if not all, of the tractive effort load... and as soon as it started... now it's over. In that respect, you will NEVER get a substantial temperature rise, and NEVER have substantial oil heating, and NEVER have any substantial powertrain loss beyond absolutely negligable... if you did, it would be because either an axleshaft was broken, or a tire was flat, and it was DRAGGING itself along... and in that case, the loss would be irrelevant with respect to that developed by a less-than-happy tire. You're looking at such a small loss, that it's not even accurately predictable, because the presence of load is only intermittant in nature.

A novel part of ANY FWA is that most of the stress that appears in an undifferentiated 4wd system occurs when the machine has Ackerman steering (front axle steers, rear axle doesn't) and is making a tight turn. That's when you break U-joints, twist shafts, and bust chains. In a hydraulic FWA system, this is rediculously simple to solve: you install a Tee in each line, and take each Tee port to a suitable valve (a common high-pressure ball valve works great). When making a really tight turn, or any other instance when you'd need to disengage the FWA system, just open the valve. It bypasses fluid from one side of the pump/motor circuit to the other, allowing both the pump and motor to free-wheel. When you're done negotiating, flip the valve closed, and you're back to full FWA.

But if you're really interested in a mechanical solution, hang a reduction sprocket setup and direction changing as necessary, then install U-joints and a shaft, and include a slip-yoke setup to allow for slop amidst articulation. I recommend you include a releasable coupling... a dog-clutch that tolerates both directions (so you have MFWA in both forward and reverse directions) but will disengage under pretty high torque if you've got it bound up bad and trying to get out of a tight spot. Off the top of my head, I'd probably dig through my box of old outboard motor gears, and see if there's a good bidirectional clutch dog in there, say... out of an old Evinrude... and see if that could be fitted into an in-out type arrangement. Unfortunately, I don't think they used those dogs in something that was going to see much more than a dozen foot-pounds, and always cushioned from shock by virtue of the propeller, but it's a start. There's industrial manufacturers of claw clutches (Renold Gear out of the UK used to make 'em for electric motors up to a few HP), but you can bet the pricetag is high. Probably best to invest lathe-time to make a custom piece out of a splined shaft and a splined coupler, but you'll need to slop-out the splines alot to make it amicable to shifting under load.

If you have to reverse direction and get a 3.3:1, you'll need appropriate gearing AND the proper diameters to get the right offset to put the driveshaft in a location that'll go forward to your front axle. You'll be spending some quality time searching for proper gears, and then plenty of time in the machine shop making all the bracketry, the gearbox, etc., which is something I consider fun, and good exercise, but for someone with a shop that isn't equipped as well as mine, would be pretty costly in every aspect.

[DaveKamp]

Tyler-

As long as you don't have big rocks frozen in the ground, ANY trencher will do a nicer job in the wintertime- rather than having rough trench walls with loose dirt, it's SHINY SMOOTH!!! I did a bunch of trenching around my farm using a very early track-driven mechanical Ditch Witch... when it was 10F outside, and frost was down around 40"... it did a wonderful job.

[Paulf]

Dave, your last two paragraphs explain exactly what I'm working on. I'm planning to use a roll pin as a shear pin as the "weak point" in case of a failure rather then a slip clutch. I'm using a chain drive at the front and rear to get the 3.3:1 reduction and a 1:1 gearbox in the center to reverse the direction and help line up the driveshaft. (A lot of figuring and thinking went into this combination -- Plan C) I have a good friend who is a machinist who has volunteered to make the gearbox for me. He says it's a piece of cake to make a gearbox and I am anxious to help him do it. Thanks for the input.

Tyler and Dave, how will a groundsaw work in mud? We've had the warmest winter and wetest year since they've started keeping records. We've had few days where the ground was frozen and then only on top. With all the rain we've had, it's been really muddy.

[DaveKamp]

In Mud... well, if there's a crust on top, it's kinda like pushing a chainsaw into apple pie.... but it looks more like French Silk... but it sure doesn't TASTE like it.

I've got this Ditch Witch (on steel tracks with grousers) and it really loved trenching frozen dirt. Problem with muddy, is that the walls cave in... regardless of the scenario, having harder dirt leaves a cleaner 'wall' cut. If the ground is wet, there's not enough cohesion to keep it from falling in.

But in any event, doing it with a trencher sure beats using a shovel...

[JLazar]

I enjoyed the rebuild groundsaw thread! That was a neat way to come up with a oil cooler from the Case 155! I would think the dozer blade is on the tractor to fill the trench, right? And to me it realy complements the whole entire tractor set up. Very interesting tool and I bet it can find much use! Thanks, John

[DaveKamp]

Hi Paul-

If you've got a guy that can make the gearbox, here's an idea:

Find a location down the length of the frame and transaxle where your driveshaft will 'fit'... and then get a center-to-center dimension between that point, and your PTO shaft. Next, look for a pair of gears that will yield your ratio AND fit that distance. There's a host of math that one could employ to calculate, but a W.A.G. and a visit to the Boston Gear catalog would get you close enough. The ratio probably won't be perfect, but tires, dirt, and the world aren't perfect either... but with that, you'll have two gears on spacing that reverse AND give ratio... then all your buddy has to do, is make a gearcase that slips over the PTO shaft, bears and contains the gears, and if you're lucky, he can put a disconnect clutch of some sort inside the box, so that you just have a U-joint going to your front axle's driveshaft.

FWIW- the axleshafts I spec'd in my driveline mods doc from years ago will probably be sufficient for the torque load you'll see, but going up to 3/4" driveshaft would be wise.

[Paulf]

Dave, thanks for the information about digging in mud. Looks like I'll wait for the ground to dry some. I'm hoping to post a video on my website when it gets dry enough to do some trenching. John, thanks for the comments. Yes, the front blade is for backfilling. Since I have a loader for that, I'm going to stick to the front weight to keep the system shorter for transport.

Dave, I started writing up the information about the 4 X 4 to put on my website this weekend. I usually wait until I've finished to publish it (always end up having to back up and redo things), but decided with the discussion here, I should do that and explain some of the decisions I've made. I got the part written up about what Rick had done when I purchased the running gear from him. I'll try to get that posted in the next couple of days. And, I am using a 3/4 inch drive shaft. Thanks for the confirmaton.

[bbaker]

I'm just sitting here thinking it would be great fun, to lock Dave, Paul F, Paul Bell, and a few others in a giant garage with a whole pile of parts, and they can only make phone calls out for food and more parts just to see what kind of monster they would come up with.

Might wanna throw Vince in the pile too, he ain't worth much, but would do whatever they told him!

[Paulf]

Bryan, great thought. Gave me a good laugh for this morning. And, Vince being there is a good idea. He'd keep us motivated.

I did manage to get Rick's part of the project on my website, cubcadetman.com. It's "FWA Original Cub Cadet" under the Special Projects section. I'm too lazy to figure out how to do the direct link this morning. But, the writeup doesn't do justice to the work that Rick put in to the project. It's just a brief recap. It's going to be a while before I get my part of the discussion on there. I have to dig through 5 spreadsheets and separate out only the relevant information.

[J Hayes]

Bryan yer Bad !!!

I think they already did that I found this in the aftermath

[DaveKamp]

Well, I'm thinkin' that'd be something the likes of Junkyard Wars and American Chopper have NEVER seen...

It'd hafta be a big shop, 'cause I'd bring all my machine tools, welding equipment, electronics and radio shop... probably take 8 semi trailers in volume... but probably 12 in capacity... to get it all there... but that'd be fine. I s'pose I could leave the 24" Lodge & Shipley behind, unless we needed to bore blocks and widen wheels... and mebbie leave the #5 Cinci behind and just make-do with the Bridgeport... between those two, that's 23,000lbs... but the horizontals, the surface grinder, radial drill, Monarch 10EE... oh, and the horizontal and vertical bandsaws both hafta come with. And the beverage fridge. And the 200-ton press, the PEXTO bender, and the blacksmith forge. I should have the CNC plasma table done by then, so include that too... fortunately, it's pretty light, just bulky. Oh, can't forget the forklift... so we can unload and load the machinery and set up the overhead crane.

What fully climate-controlled aircraft hangar did you say you were buying for us to move into, anyway?