Mini Dozer - Project near complete

mcd176 · Nov 16, 2009

Very Very cool project!

Oldmax · Nov 16, 2009

I was wondering the same thing about mounting the motors direcly on drive shafts.

workinprogress · Nov 16, 2009

I haven't gotten things welded up yet or the addtional plate added but I have put the correct spacers onto the 3rd pillow block. The alignment looks much better now (Look that the earlier photo).

wldrbob · Nov 16, 2009

hi nice looking unit .turn an angle iron over and box in your first two outside pillow blocks also you might need to put caps on your pillow blocks as on my skidhoe i pulled the tops of of 1.5 inch pillowblocks. the 3rd pillow block will take out a lot of movement but if you have any deflection in your track frame you will get stress cracks over time. seems like you have room to bridge your frame it will pay of later because your tourke will go up a lot once you start pushing stuff around and we all know how much fun that is .... wldrbob

Renze · Nov 16, 2009

Ductape said:
Probably too late for the current build........... and maybe way out of budget, but how about a high tracked version like the modern Cats? You could drive the third (high) sprocket, and this would keep your drive chain / driven sprocket way out of harms way. The rear-most idler could be put back a bit farther and therefore the tractor wouldn't feel so rear-heavy. Just thinking out loud here.

My thought as well.. with a high sprocket drive, you could simply pick a smaller sprocket and do away with the extra chain drive.

Danno1 · Nov 16, 2009

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Yes, slack side depends on fwd/rev. So, put a tensioner on both sides! The tension side will move and the slack side will take up the slack.

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sizzami · Nov 17, 2009

are you going to add any bogies? it looks like the tracks ar very wide inrelation to the sprockets how does it perform undr load?

workinprogress · Nov 17, 2009

A few comments:

I also agree that mounting the motor directly on a third track sprocket like the Cat would be good but mostlikely would involve creating more track. The 10ft roller chain may not be enough. Also I would need to find 100 pitch sprocket with a small number of teeth at a fair price. I think I will keep the current plan for now and see how it comes together. That being said I will keep my eye out for a good deal on 2 100 pitch sprockets with an 1 inch hub.

I am going to put boggie wheels on the unit but I need to find a small strong wheel. Been looking at some heavy duty caster type wheels but still a work in progress. If I ride the boggie wheel directly on the chain it will have to account for the ups and down of the links on the roller chain. So I go back and forth about placing the boggies on the roller chain or pairs of them on each side of the chain. I am leaning toward the pair because I think it would help support the track when a rock or something is only under one side of the track.

The track seems to move fine even with the single track sprocket. I have been able to put some good tension on the track so it doesn't seem to twist.

hammerdwn20 · Nov 17, 2009

workinprogress said:
A few comments:

I also agree that mounting the motor directly on a third track sprocket like the Cat would be good but mostlikely would involve creating more track. The 10ft roller chain may not be enough. Also I would need to find 100 pitch sprocket with a small number of teeth at a fair price. I think I will keep the current plan for now and see how it comes together. That being said I will keep my eye out for a good deal on 2 100 pitch sprockets with an 1 inch hub.
I know you got your sprockets from surplus center and i was looking there the other day. They had a few types in the 8 1/2 inch diameter. some tapered hub, 3/4" bore and some in 2 1/2" bore. maybe you could put bearings into the ones with the 2 1/2" bore

I am going to put boggie wheels on the unit but I need to find a small strong wheel. Been looking at some heavy duty caster type wheels but still a work in progress. If I ride the boggie wheel directly on the chain it will have to account for the ups and down of the links on the roller chain. So I go back and forth about placing the boggies on the roller chain or pairs of them on each side of the chain. I am leaning toward the pair because I think it would help support the track when a rock or something is only under one side of the track.
I had thought of caster wheels when i was thinking about building a crawler also. I can see your point on the double rollers but also consider the rocks and dirt they will be riding on as that area get a lot of dirt in turns. it might be better to ride on the chain. Id also cut holes into the track pads where the teeth engage the chain. dirt needs to be pushed through there or you will throw a track

The track seems to move fine even with the single track sprocket. I have been able to put some good tension on the track so it doesn't seem to twist.

Keep it up it looks good

wldrbob · Nov 17, 2009

how about some uhmw plastic and just make sliders on each side of your center chain no wories about bogie wheels then just like a skidoo slider inside the track. 2.5 or 3 ft sliders would fit just nice and that stuff takes forever to wear out and it stays slipery

David Devuono · Nov 18, 2009

When I built my tracked wheel barrow I had not end of chain problems until I added a tentioner. It does not so much as add pressure to the chain as it allows the chain to wrap around the drive gear more. My chain would ride up on the drive gear and then jump a tooth with a loud crack. I am also collecting pieces for a mini dozer\dump cart. Thanks for the ideas.

Danno1 · Nov 18, 2009

wldrbob said:
how about some uhmw plastic and just make sliders on each side of your center chain no wories about bogie wheels then just like a skidoo slider inside the track. 2.5 or 3 ft sliders would fit just nice and that stuff takes forever to wear out and it stays slipery

+1

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David Devuono · Nov 22, 2009

My plan is to build a small dozer with a dump bed. Problem is I can't take all day to drive from my sand pit to the end of the road. I would really like to see a short video. What size pump and what Horse Power motor? How fast will it go flat out? Will it spin one track forward and the other in reverse at the same time or will it stall out or do it very slowly. I don't want to by two motors so need to get one big enough. I would be happy with 5mph (8kmph). Ready though a lengthy build on Machine builders network, the fellow had to enclose the drive chains with covers as small rocks caused chain problems.

Renze · Nov 22, 2009

David Devuono, why not buy a Honda motorised wheelbarrow with rubber tracks ?? it already has a dumpbed. All you need to add is a dozer blade and a decent operators seat so you dont have to walk behind them.

About the track sliders, if you make them run on the chain rollers there is even less friction.

wldrbob · Nov 22, 2009

hi there would be less friction on the track rollers but i dont think they would stay in place on hard turns and rough ground on each side would keep the track level to....bob

workinprogress · Nov 22, 2009

Took longer than I thought but I have things back together at least until the boggie wheels I ordered come in. I straighten the bent angle iron and welded 1.5x1.5 angler 1/4 thick on top of the part that bent. I also placed a third pillow block on. Once everything was put together I took a piece of flat stock long enough to between the drive sprocket like a straight edge. I made slight ajustments on the sprocket alignment so the flat stock have good contact with the sprockets. The resulted in about a 1/8 inch adjustment on one side and close to 1/4 inch on the other. I took a test run into the woods and looked for something to pull. The drive chain never came our in close to 20 minutes of playing. I put a chain onto a big flat rock and tried to drag it. The ground was soft and I couldn't get the rock to move (not sure I should expect the machine to move it) but I did dig some nice holes with the tracks. Gave up on the rock and drove back to the wood shed. Not sure the boggie wheels will be here before thanksgiving but will post pictures then.

Answers to a few questions Posted:
Speed - Currently the dozer zips along around 2.5 mph. With the boggie order I also have additional sprocket to try and gain a little more speed. Currently 3.4 to 1 ratio will try 2.4 to 1. Good site to check gear ratios and RPM to speed. Baum Hydraulics Corp :: Spec Calculator

Controls - The track are indepent of each other. One can go forward and the other reverse. At the current gear ratio there seems to be little impact to the gas motor.

Other specs: Pump/control - 0.43 CI for each motor. Hydralic motor 6.0CI, and unit is running off a 12.5 HP kawaski motor. Even at 1/4 throttle I can run one motor forward and one reverse. Drive Gear reduction - 3.4:1. In version 1.0 I ran 1.93 CI hydraulic motors, they had good speed but did bog down.

Questions: For those people suggesting direct drive with the upper (CAT type) drive design any thoughts how much sprocket contact do I need. I looked at things might be able to sneak a small drive sprocket right on the track but with the current track length and configuration I would only have 1/3 or so of the sprocket in contact with the track chain contact. Would that be enough?

Thanks for all the suggestions. I still need to work on the drive chain spring tensioners but wanted to get the boggie wheels on first.

PILOON · Nov 22, 2009

For idlers you could use smaller (same pitched) sprockets, say 3 per side and mount them between some serious enough flat stock (3/8 X 2-3") with only the teeth protruding.
Then you could attach to the upper track structure with perhaps some side bracing to keep them centered.
This way you'd always have good ground contact without streatching your track chains.

Otherwise real fun project, wish I were doing it.

Mace Canute · Nov 22, 2009

The recommended minimum wrap angle of the smallest sprocket in the drive is 120°. The wrap angle can be reduced to 90°, if good chain tension adjustment is maintained. If chain tension is not closely maintained with less than 120° wrap, the chain can jump teeth, resulting in damage to the chain and/or the sprocket. Also, the usual recommendation is a minimum of six teeth engagement.