tracked vehicle differential questions

[Iplayfarmer]

I wish we could "find" used equipment like a golf course mower, they must go to employees as I never see anything up for sale. Maybe I should stop by and ask, there are about 6 of them in a 30 min radius.

You'll probably have to ask. The defunct mowers are usually in a pile of weeds behind the maintenance shack. Figure out who the decision maker is and offer him $100 or so for the old mower. With 6 courses you ought to find at least one bad mower in there.

I lucked out and found a guy who was converting his golf course back into farm ground (no idea why). I paid $200 for two reel mowers. I've poached engines, hydraulic motors, wheel motors, cylinders, wheels, seats, and just about everything else off of these old machines. I have also sold a few parts and made at least 3 times what I paid for them. They're a great source of hydraulics.

 

[SensibleNick]

Understood. I can totally respect that.

Part of the fun for me on a creative build is re-purposing old parts rather than buying new. For some reason I feel like I get extra creativity credit for using old parts.

.. and in turn, I can totally respect that

There are many cases where I do the same - so far most things I've built for my tractor are from scrapped metal at work - but for some reaon on this one I want shiny things! :ashamed:

WOW.. good advice there IPF... Good luck Dave!

I think it was Abe Lincoln who said "Good things may come to those who wait, but only the things left behind by those who hussle":thumbsup:

 

[oughtsix]

I like the two stick control idea also. This imposes some limits on where the driver position is in relation to the twin hydrostatic pumps or you could end up with a headache for linkages. I have considered mounting a small hydraulic cylinder to each control stick then plumbing them to another pair of cylinders on the twin hydrostatic pumps. Pretty much a clutch master / slave cylinder arrangement x 2 that would allow a lot more flexibility in mounting the control sticks.

It would seem to me you could individually control the brakes on each side of the diff with levers linked to hydraulic cylinders.

I like the look of the 1cu hydrostatic pumps on surplus center. I like that they are setup for direct drive or belt drive. That gives quite a bit of flexibility. I have a twin inline hydrostatic pump like the first one you mentioned. It doesn't have an accessories pump currently but it does have a removable cover for adding one or more. I scored the pump for $300 brand new... it was a replacement for a skidsteer that never got used. It doesn't have an original manufactures part number on it though which leaves me guessing a bit on its actual specifications. I am pretty confident it was originally in a direct drive application so I am hesitant to belt drive it.

I have a 1.6l carbureted Toyota engine with 83K miles on it from my mother in laws car sitting in my garage. I thought a 1.0l 3 cylinder Geo engine would be perfect as far as power and weight but the 1.6 was free. I was planning on a 3 piece flex coupling to mate the dual hydrostatic pump. This will give me a little fudge room when trying to align the pump to the motor. Like I mentioned before mating the motor to the pump is my current issue.

There is a Mercedes 2.4l diesel engine and transmission on my local Craigs list that started at $700 and has fallen to $275 currently. I was thinking of picking this up but is would add way too much weight. I like the 1.5 diesel engine idea... I had thought about a 1.6l VW diesel myself before the free Toyota engine came along.

I would love to find a golf course mower to scavenge... but they are WAY to proud of their used equipment in my neck of the woods. The old Toro or Jacobson commercial stuff is a few thousand dollars for not or barley running equipment.

 

[SensibleNick]

^^ Sounds like you're walking the same path as me, but a few steps ahead

The 1.1CuI pumps at surpluscenter really do look great to me.
And as far as your extra hydraulics are concerned, a small pump driven by the engine's alternator or fan belt would be great.

Friends keep trying to railroad me into getting a 2.5liter Mercedes straight 6 for the project, but that is WAY too much power for my needs.

40HP at the PTO would be fine, and I've calculated that with the smallest wheelmotor and the largest stand-alone hydrostatic pumps that surplus center have, I'd have a 40kmh top speed and enough torque to effectively "pull" each track forwards with 1.5 tons of force. (too much power... I'd happily sacrifice torque for more RPM )

So.. the hunt for a small diesel is on. Maybe I could build with a small petrol to start with and wait for the "dream engine" My "Daily Driver" is a 1.3l turbo-diesel producing most of it's torque between 1500 and 4000rpm. Utterly perfect... (75bhp and 75mpg) but finding one of those engines is going to be nearly impossible, and it'll come with all sorts of problematic wiring that I want to avoid. Maybe a small Carbed Petrol running on Ethanol?

Linkages: I think perhaps you overestimate the complexity that you'd need. using hydraulic cylinders will remove all feeling you might have, and is WAY more complex than levers/rods.

 

[oughtsix]

Have you checked out the 51hp Lombardi diesel on surplus center? It makes me drool as it would be perfect! But $4200 US is too rich for my blood.

Surplus Center - 51 HP LOMBARDINI DIESEL ENGINE

If you can make the engine mount modular enough and design it for the dream engine a gasser (petrol in your world I believe) might be a good start. I look at it as how much gas could I buy for the price of the dream diesel engine? $4200 will get me a mighty long way. But I would love the torque characteristics and fuel efficiency of a diesel!

My parts are from three plus years of collecting and mostly from ebay. I have collected 7.5ci, 15ci and 24ci wheel motors. I figure that I can vary the engine speed / pump speed and wheel diameter to get in the running range I am looking for since I don't really know the displacement of the hydrostatic pumps. I couldn't resist the pair of torque hubs (the grey ones) as they were just to good of a deal to pass up since they are brand new and already have attached hydraulic motors and integrated brakes. I think they would be better suited for a bulldozer project though.

I am not overly afraid of engine wiring but it would be nice to get something running without having to worry about electronic injection and fuel computers. The Toyota engine is an 86 and the carburetor is literally a bastard. It is a feed back carb so it self adjusts based on readings from an O2 sensor. A cross between a real carb and fuel injection. I haven't figured out if I can just plug off all the extra vacuum ports or if I am going to need to replace it with an old fashioned carb.


How big of a drive sprocket could you effectively use to drive the tracks? You might be able to increase the top speed a bit by increasing the sprocket diameter?

The smallest wheel motor Surplus center has is 7.4ci. I would really encourage you to look at the 7.8ci wheel motors though as they have much better bearings in them... which might not be of any concern to you as I don't believe your wheel motors will be weight bearing. The pumps are 1.1ci. So you should get about one revolution of the wheel motor for every 6.7 revolutions of the pump / engine. So 3000rpm / 6.7 = ~446 rpm maximum speed at the wheel motor. With a 14 inch sprocket I get about 18.6mph or about 30kph. With a little faster pump speed and a little bigger drive sprocket I can see where your 40kph is coming from.

If you could use a non-wheel motor in the 3ci to 5ci range it seems like you could have a lot more fun! My understanding is the hydraulic motors that aren't specifically made as wheel motors don't usually have any bearings for handling side loads. So you would have to build a self supporting shaft to mount the drive sprocket on and then mount the motor to drive the shaft. This way the shaft takes all the side loads.

The pumps are rated at 3600 rpm max. Are you thinking of direct driving your pumps or chain/belt driving them? It seems like a chain drive would allow you to run the pumps at near their top speed without chugging down the fuel due to running the engine at the same 3600rpm speed.

I had considered direct driving the pumps off the output of the motor transmission which would also cut down on the engine speed if the transmission was a manual with an overdrive. This wasn't possible with the engine I have since the transmission was an automatic and an integrated trans-axle.


Hmmm.... I still think Davedj's design will be a lot quicker to build.

 

[SensibleNick]

answers in Red to avoid confusion...

Have you checked out the 51hp Lombardi diesel on surplus center? It makes me drool as it would be perfect! But $4200 US is too rich for my blood.
I have, and 4200 is silly money for me too: I'd rather hunt down a perfect plant here in Sweden... posting Diesel engines across the Atlantic seems... um... wasteful

If you can make the engine mount modular enough and design it for the dream engine a gasser (petrol in your world I believe) might be a good start. I look at it as how much gas could I buy for the price of the dream diesel engine? $4200 will get me a mighty long way. But I would love the torque characteristics and fuel efficiency of a diesel!
Old diesel cars are rare here due to a road-tax for Diesel cars that *used to be* higher than the petrols. Diesel Is my goal, although I'm a dab-hand at tinkering with Petrols. I want something that chugs away happily

I am not overly afraid of engine wiring but it would be nice to get something running without having to worry about electronic injection and fuel computers. The Toyota engine is an 86 and the carburetor is literally a bastard. It is a feed back carb so it self adjusts based on readings from an O2 sensor. A cross between a real carb and fuel injection. I haven't figured out if I can just plug off all the extra vacuum ports or if I am going to need to replace it with an old fashioned carb.
Measure the carb diameter, and find yourself an old SU carb that'll do the job. I'm sure there are a million and one friendly tuners out there who'd tune a groovy-looking machine for free. a 1.75" Hif might do the job.


How big of a drive sprocket could you effectively use to drive the tracks? You might be able to increase the top speed a bit by increasing the sprocket diameter?
I'll be using the standard drive.sprockets from the BV202 track system. From what I can work out using old data, photos and diagrams, they have a 420mm OD. That's roughly 17".

The smallest wheel motor Surplus center has is 7.4ci. I would really encourage you to look at the 7.8ci wheel motors though as they have much better bearings in them... which might not be of any concern to you as I don't believe your wheel motors will be weight bearing. The pumps are 1.1ci. So you should get about one revolution of the wheel motor for every 6.7 revolutions of the pump / engine. So 3000rpm / 6.7 = ~446 rpm maximum speed at the wheel motor. With a 14 inch sprocket I get about 18.6mph or about 30kph. With a little faster pump speed and a little bigger drive sprocket I can see where your 40kph is coming from.
You're spot on. I've built myself a little Excel sheet with all the data in it for the pumps, and have gone though the exact same figures as you
the 7.4cu pumps are the ones I'm considering for exactly the reason you mention: my "wheel" motors won't support weight. All they'll do is provide drive to the tracks. As such, I expect any wheel motor to survive in that application. No shock-loadings, no huge radial loadings... should be a great life for them


If you could use a non-wheel motor in the 3ci to 5ci range it seems like you could have a lot more fun! My understanding is the hydraulic motors that aren't specifically made as wheel motors don't usually have any bearings for handling side loads. So you would have to build a self supporting shaft to mount the drive sprocket on and then mount the motor to drive the shaft. This way the shaft takes all the side loads.
I have considered this too, but opted initially for the simplicity of a wheel motor. As I plan to tension the tracks by moving the wheel-motor-mount forwards, I will have a modular front section to the track pontoon. This idea is also born from the potential next step of a higher speed/lower torque setup using - as you suggest - smaller volume motors and a gear/chain drive. I might also offset the wheel-motors and run a MC chain from them to gear things up - another fun sub-project for the summer evenings.

The pumps are rated at 3600 rpm max. Are you thinking of direct driving your pumps or chain/belt driving them? It seems like a chain drive would allow you to run the pumps at near their top speed without chugging down the fuel due to running the engine at the same 3600rpm speed.
Motorbike Chain. Without a doubt. I want to be able to play with the gearing, and I want to be able to change the gearing depending upon snow-blower or snow plough usage. I'll most likely run double-sprockets to allow me to de-tension the chains and change gearing: much like a pillar-drill. The pump "assembly" will be driven by a driveshaft form the clutch assembly on the engine, allowing a whole host of potential engines to be fitted in the space available. Whether I keep the engine's clutch or not remains to be seen - but I feel it might be useful.

I had considered direct driving the pumps off the output of the motor transmission which would also cut down on the engine speed if the transmission was a manual with an overdrive. This wasn't possible with the engine I have since the transmission was an automatic and an integrated trans-axle.
That's a shame. Ditching the gearbox will save mass, and decrease mechanical losses - it's what I intend to do. Auto-boxes are a PITA.
Have you considered the engine from a VW beetle/bug? Nice, low, aircooled, light, and as mechanically complex as a hammer. Given the amount of people in the US putting porsche engines in beetles, I'm sure there's some old VW lumps out there for cheap... and they're SO reliable that people put them in aeroplanes. If I were going Petrol, I'd be seriously tempted by a Harley engine...

I intend to have a rather high capacity pump for the hydraulic PTO shaft motor... and I'm wondering whether a hydrostatic pump is the way to go, or a gear pump and a motor control valve. I just get the feeling that permanently pumping fluid with a gear pump is wasteful.. .. but the 1.1cu HS pumps at SurplusCenter don't quite cut the mustard when it comes to getting a 40hp output... Have you given any thought to this?


Hmmm.... I still think Davedj's design will be a lot quicker to build.
Without doubt. But it will be far harder to make radio controlled, and won't present as many of the challenges that I enjoy.

I don't know if I've mentioned this before, but I'm a Mechanical Engineer, and big slow stuff like these machines are a pure joy to play with compared to the stuff I get *paid* to think about :laughing:

 

[SensibleNick]

Sorry Dave: Hope it's ok to discuss my crap here too... Tell me if you want to stay on track (see what I did there? ) and I'll start my own thread

But.. I think I've found the perfect engine. The TUD5. - Very common here in Europe, and it's possible to bang a turbo in it too (if you get bored)

The indirect injection 1527cc oil burner develops 57bhp at peak revs of 5000rpm and torque of 95Nm at 2250rpm, the torque curve being relatively flat from 2250rpm to 3500rpm and then tapering off.

:thumbsup:

 

[davedj1]

Nick, you are more than welcome here, I am enjoying all of these posts and I'm learning more than I thought I ever would.
Keep the head spinning info coming...LOL....I'm no engineer!
dave

 

[SensibleNick]

:thumbsup:

Nick, you are more than welcome here, I am enjoying all of these posts and I'm learning more than I thought I ever would.

 

[oughtsix]

My top pick for an engine would be a diesel. My top pick for a gasser was a 1.0l 3cyl Geo engine (also made by Toyota) mainly due to the size and weight. A VW bug engine was also very very high on the list! I live in Oregon and we have a wealth of Bugs, there engines and the hippies that go along with them. There simplicity is a big plus... but I believe there best attribute is the number of different applications they have already been retrofitted for and the amount of available parts for performing those retrofits. Like you mention people have put them in airplanes so they have already worked out the mounting and drive linkage issues. I like the guys that run them on two cylinders and use the other two cylinders as an air compressor pump... cool idea! I don't know my air cooled VW engines very well but the lower displacement ones seem to be pretty cheap since people always want to upgrade to the larger displacement engines.

I can't find a lot of info on the TUD5 other than it is a Peugeot.

Yes! I have considered using a hydrostatic pump to drive the accessories. My dual pump has some standard SAE mount on the back for adding another spline drive pump. I think a variable volume pump would be excellent for the versatility it would give you! How many accessory hydraulic circuits are you planning on having? I would imagine a high volume circuit for the snow plow and some lower volume circuits for raising, lowering, tilting etc. What are your thoughts on running two accessory pumps vs some kind of spool valve?

I have no hands on experience with hydraulics... just a whole lot of reading and research. That said: I really like this pump http://www.surpluscenter.com/item.asp?item=9-7686&catname=hydraulic As a low volume accessory pump. I have visions of proportional speed control on raising/lowering arms etc. At $129 I can barely pick up a hydraulic valve for that. .43ci is too small for any drive application I can think of... but perfect for moving a large cylinder... and they are reversible! It seems like the pump could almost pay for it self just in the cost savings on hydraulic hoses? (Yes, the volume differential in the side of a cylinder with the shaft and without the shaft does give me concern).

Are you thinking one chain to drive both pumps or one chain for each pump? How will you drive the accessory pump(s)?

I agree with the hydraulic wheel motor for your application. The amount of complexity and failure points it saves will hopefully outweigh the speed issues. I haven't come across wheel motors with a lower displacement than 7ci in my searching... although I wasn't specifically looking for any. A 17" spocket seems like it should give you a pretty decent top speed. I guess it all depends on what your target top speed is. My target is a top speed of 15mph with a run speed around 5mpg.

You lost me on the SU carb and the 1.75" hif carb? I am not familiar with those? I was thinking along the lines of a Weber carb as they are popular retro fits for many engines like the VW's. After it is running I will probably mess around with converting it to fuel injection.. as I enjoy playing with fuel injection: Mercedes 450slc with MegaSquirt fuel injection

I also agree with ditching the the gear box for weight and efficiency. I am pretty handy but fabbing the pump/motor mount is a stretch for both my skill set and tool set. The starter is located in the bell housing. If I loose the bell housing I loose my starter mount too. I like having the clutch for unloading the motor during starting and idling. I am worried about my ability to align the motor and pump shafts accurately. I know I can use a coupling like these to give myself a bit of wiggle room:

But, from what I have read I have to get the alignment pretty close or I will be replacing the rubber bushing quite often.

I am a systems programmer by trade... so you can factor that into the weight you give my comments and ideas. After sitting at a desk all day staring at a monitor it is a great stress relief to get my hands dirty!

P.S. I really enjoy discussing this stuff with whoever feels like contributing. A new point of view to consider is always very valuable. Thank you for your patients with us HiJaking your thread Dave!