New project - 4WD Articulated Tractor

[Spiffy1]

Originally Posted by Spiffy1

The other thing, are the left and right wheels for each "axel" in series, not sure if I'm reading your schematic correctly though? I think, front and rear generally are in series so the 2 tighter circle tires can turn at the same rate and ditto on the wider circle.

On second glance, I think your schematic does show the sides in series and "axels" in parallel with your "posi-trac" valves at the T-locations.

[Mith]

Spiffy, thanks for the thoughts and the pic -

I understand that some of the larger CAT equipment uses motor oil in its hydraulic systems, so I don't think there is anything wrong with it. Not sure how they go about the non-foaming issue, maybe they add additives?
I guess you arent putting just any old oil in yours, do PT spec oil for it?

So you have the same pump for steering that you use for your loader? Does that mean that when the steering hits the relief the loader stops?
I weighed up the options for using the same pump for accessories and steering. In the end decided to spend $300 more and get a separate pump. Not too sure at this point if it was worth it.

You are exactly right on your analysis of the fixed disp pump with a valve and the variable disp pump. I think the pedal will work more like a power pedal than an accelerator pedal. Press the pedal more and the pressure to the motors increases. If the pressure is more than is needed to move then you go faster. It might be weird to drive, but hopefully it'll work. Variable disp pumps were big money, $2k for something that might have worked.
Thats the part that I am most intrigued to test, this project is really an experiment every step of the way. My drive pump is 68l/min (18gal/min) and I'm hoping the tank will be able to cool that flow. In all probability I wont be running all full engine speed, so the flow will be far less. I'm only running about 1500psi full pressure too.
Using your calculation, at full speed and pressure I will be about on the money with my 31HP engine. Adding a hydraulic PTO would probably be too much, its an option for down the line though.

The wheels on each axle are in parallel to allow for different speeds when turning. The 2 axles are in series. As you say, the diverters just replace a T in the lines.

Thanks for your posts, its handy to be able to compare my system to a proven design, interesting analysis too.

[Mith]

I think this has all the bits on it and is right.....

[quincy]

Have you seen this video clip Mith?

http://www.steinerturf.com/videos/43...ractor-hi.html

[Mith]

Quincy, yea, I spotted that. I think the steiner uses a hydro drive and 2 diffs rather than all hydraulic drive. Nice machine though.

Spiffy, I remember why I thought the fixed disp pump and valve setup would work now. The CADtrac uses that setup, I had a word with some owners and they were quite happy with the operation. I'll be sure to let you know what its like, nbot expecting it to be good as a variable disp pump setup though.


I tore the tractor down and painted all the chassis. Just working my way through assembling it all now, and then hosing it all.
I added some sheet metal onto it, a bit on the side of the dash, and also the tunnel through which the hoses run.

[quincy]

Originally Posted by Mith

Quincy, yea, I spotted that. I think the steiner uses a hydro drive and 2 diffs rather than all hydraulic drive. Nice machine though.

Thought it might give you some ideas for the tin work when you get to that stage.

[haffasst]

Mith, it looks great. One hell of a project. Can you get a pic of the articulating point? Just nosey-----LOL

[Mith]

Qunicy, true, I hadnt thought about the sheet metal on them. I'll have to find some closer pictures of how its formed around the engine.
I have been looking at the Struck crawlers. They have the same engine and a similar pump setup, so the bonnet is similar to what I'll need.

Haffast, there are some pictures at the beginning of the thread. The following one is about the best I have. When I assembled that joint I didnt have a camera, so not too many photos.
The rear section has a 1.75" pin welded into it, the front section has plates with bushings attached. The bottom plate is bolted so you can take the joint apart.





Started doing the hydraulic plumbing today. Its pretty involved. Looks like an accident at a spaghetti factory in my workshop at the moment.
So far its going well. I'll have to modify part of the dash board structure to fit in the suction hose for the drive pump, this is the problem with designing a structure to fit parts you dont have to hand.
My exploits in the workshop are starting to get noticed, got an interesting fabrication job to go see about later on in the week.

[Mith]

Done lots of plumbing. Routing the big hoses is like wrestling a snake, its quite hard to scale, but the big hose in the pictures is about the same size as my wrist. Just fitting in 10 mins here and there at the moment.

Sorry about the picture quality, its very dark in the w/shop. I'll try and take the next ones when the sun is up so its a bit lighter.

Got a hydraulic PTO motor. Probably a bit big, but the price was right. Its massive, weighs easily 100lbs if not more. Its next to a K62 trans (in bigger garden tractors) in the photo for scale.

[haffasst]

Mith, Thanks for the pic's. Nice work, I wish I had your talent.

[Mith]

Haffasst, thanks. If you want to do a project like this, my advice is to just go ahead and give it a try. When you break it down, and with the help of people on forums like this one its amazing what you can achieve.


Well guys, its real close!
Sadly, I messed up and ordered 5 of the hoses wrong. So I have to wait for new ones to come. Ordered one 4" too short, and 4 with the wrong ends. I could have had it going this weekend..... Never mind, I would have probable been rushing to get it done this weekend if they had of been right, less mistakes when I take my time.
Just got to fit a few more hoses, make a steering wheel boss, make a battery box, fit the fuel tank and do the wiring. I might even bleed the suction lines through in anticipation of the hoses coming next week

I'll be watching for the dust cloud first time you take her out for trials!

[Mith]

Fired it up for the first time today! Could do little more than twitch the steering as its on axle stands awaiting the final fittings, but atleast it does something
I had forgotten to tighten one fitting on the steering, a large shower of fluid later that was sorted.

Not really all that exciting in the scale of things I suppose, but I've spent thousands of pounds on it and thats the first sign of life, I'm over the moon. Lets hope the last few fittings I need turn up soon!

If I can get it to do something more exciting I'll take a video tomorrow. My camera doesnt have sound, but apart from the engine there isnt much to hear.