My Senior design project - a "Swamp Thing" tracked vehicle clone

[ArlyA]

Hydraulics are not more efficient or stronger in any way, but they are cheaper to build our machines with.

Thanks ArlyA: I have seen that video a number of times. It’s very well done.
Hydraulics often introduces inefficiencies but that has to be weighed against mechanical ineffiencies of mechanical systems where a lot of gearing is used to reduce the speed and increase the torque between an engine and wheels or track.
I’ve seen huge motors, delivering thousands of ft.lbs. of torque to winch drums or bull wheels on ski lifts simply because they are more efficient and provide easy changes in rotation and speed. It’s the faster lighter machinery where the mechanical gear boxes shine. Hydraulics is best for great lumbering machines or where compactness and remote force is needed, such as the wing flaps on a 747.
Love discussing this stuff. Learning all the time.

 

[MossRoad]

Hydraulics are not more efficient or stronger in any way, but they are cheaper to build our machines with.

Hoses are easier to route than mechanical linkages, too. And a lot more flexible.

 

[balsam]

Hoses are easier to route than mechanical linkages, too. And a lot more flexible.

For sure. Usually a lot lighter also and for my application it痴 important.
Enough can稚 be said as to your point of hoses or tubing versus mechanical linkages. The power unit can placed in more convenient places as well as the actuators.
Each has it痴 advantages.
Mechanical design is often a trade off. In my case I am trading a little efficiency for convenience, weight and space saving. Also I can do it cheaper using brand new components.

 

[Garauld]

I spent most of this past week futzing with trying to get the outboard CV joint apart. I first tried to use the press (puller) design in the photo I posted earlier. I bought a group of 8 grease hoses off EBay - these normally have a working pressure of 3-5000 psi - I figured that should be enough for my two rams to pull the CV apart. Wrong. I hooked up the puller press with the grease hoses to my Porta-power hand pump and gave it a try. After a few pumps I saw the lines tighten up and then BAM - a stream of light yellow hydraulic oil went pissing across my shop when one of the grease hose fittings blew off. I tried another and another - nope. OK, let's try plan B - I have a nice Jet 35 ton hydraulic press that will move just about anything. I reconfigured the puller press rig so it could be used in my big press which, BTW, has a load gauge on it. I got everything set up and gave the pump a few pulls until it registered about 3 tons. A couple more tugs on the arm and something was moving and it wasn't the gauge. My CV puller support was bending. I took it all apart and welded a 3/8 x 1" bar on each side of it after I re-straightened it. With everything back together, I pumped the press up and saw 10 tons until the CV broke apart - the metal cage that held the (6) CV balls in place split in two. The dang snap ring inside which was supposed to compress back into it's groove on the axle didn't. I'll just have to reweld the axles back together with the CV hub mounted. In the worst case scenario, I'll need to buy a pair of shorter custom CV axles.

Today, I machined the (16) drive sprocket teeth and drilled the holes in the drive for the mounting bolts. The teeth are made from Tivar. Here's my machining setups:



Tomorrow, I hope to start work on the driveshaft.

 

[jmc]

Nice machinery. Nice work. Did you post a picture of the tracks this meshes with?

 

[Garauld]

Did you post a picture of the tracks this meshes with?

-> the very first post in this thread has a photo of the overall design with the tracks.

 

[Garauld]

A little bit of progress has been made. I have the red service brake calipers installed and the seat frames are done. I'm working on welding up the cab frame this week.

 

[The Fred]

You can buy Chinese cheap crap axles for that thing under $100 bux each. Not sure of you application.

Front Complete CV Axle Shaft Assembly LH Driver Side for Echo xA xB New 192659739131 | eBay

 

[Garauld]

I plan to use the OEM Rav4 half axles coming off the forward Rav4 diff and shorten them myself. If they break, I can buy stronger custom axles that will fit perfectly. As for the driveshaft, I will use an OEM Echo half axle, cut it and weld it to a piece of pipe cut to my needed length. I can buy a custom driveshaft if needed later. Let's see how it drives first before spending extra bux.

 

[balsam]

You can buy Chinese cheap crap axles for that thing under $100 bux each. Not sure of you application.

Front Complete CV Axle Shaft Assembly LH Driver Side for Echo xA xB New 192659739131 | eBay

Garauld: Realy nice, neat work your doing. I知 sure youæ±*e going to be very pleased with it. I知 looking forward to seeing it running. I see your going to put together your own tracks. I may do the same but I have been searching the internet for information on suitable ones. They show width, pitch and lengths but nothing about thickness and weight. Ones for mini excavators and skid steer equipment are pretty heavy duty. Of course, snow machine ones are not long enough even though my plans are to keep the tracks as short as I can to keep the torquing on the frame low as and to improve the steering....much less horsepower to rotate around shorter tracks as opposed to longer ones.
Haven稚 done much on mine yet but have found an engine I may purchase. It痴 new, so not cheap. I don稚 mind spending money on this project. I think if I keep it under the price of a new snow machine I can keep my marriage together. I want to be safe and comfortable ice fishing.
I ran my hydraulic circuit ideas by some friends in an engineering office here and they seem to think it should work fine....much like yours. They had a couple of good suggestions also, with regards to the circuit, mainly about braking. One guy suggested I consider doing the frame out of aluminum which I have been looking into. I haven稚 welded aluminum for some time but I do have a good mig machine so I may purchase a spool gun and see how I do. Anything I need tig for, I can get done at a shop here.
Please keep the pictures coming.