Mini Dozer - Project near complete

[Renze]

hmm... i just read back and deleted my comment about the slackign chains, at it wasnt the track chain but the motor to track drivechain...

An extra bearing might be good. Just dont use V belts, they are just a pain in the @rse. Old 3 ton JF manure spreaders had a belt driven beater, which was a crappy construction because despite the shields, the belts still would catch a bit of muck, causing them to slip every time. V- belts do work, but they need a lot more tension than a chain. So you'd need more bearings, or a bigger shaft anyways.

I do recommend some extra idlers between those main sprockets, the span force is enormous: just imagine you and your friend spanning a rope horizontally over a 5 yard distance, and your 7 year old kid wants to hang in the middle of it: You would need 10 extra men on each side of the rope to keep your kid off the ground at that span width, let alone pulling it horizontally !! Thats whats happening when you drive over a bump, when the tracks are spanned between two rigid sprockets.

 

[ultrarunner]

hmm... i just read back and deleted my comment about the slackign chains, at it wasnt the track chain but the motor to track drivechain...

An extra bearing might be good. Just dont use V belts, they are just a pain in the @rse. Old 3 ton JF manure spreaders had a belt driven beater, which was a crappy construction because despite the shields, the belts still would catch a bit of muck, causing them to slip every time. V- belts do work, but they need a lot more tension than a chain. So you'd need more bearings, or a bigger shaft anyways.

I do recommend some extra idlers between those main sprockets, the span force is enormous: just imagine you and your friend spanning a rope horizontally over a 5 yard distance, and your 7 year old kid wants to hang in the middle of it: You would need 10 extra men on each side of the rope to keep your kid off the ground at that span width, let alone pulling it horizontally !! Thats whats happening when you drive over a bump, when the tracks are spanned between two rigid sprockets.

WE built a lot of equipment with cog belting in place of v-belts and chains... seem to work very well... just a thought

 

[J_J]

Nice work, almost looks like my Magnatrac mini-dozer.

 

[workinprogress]

Well I found the issue today. It seemed the motor mounts may be fine I bent the sub frame. If you look at the first image "Bend Top view" you can see a arrow pointing out the bend. On the other image "bend and proposed plan" which is a view from behind.

Basically I am onto Version 4.0 and will need to straight the angle iron. Weld on additional reenforcement plates (either 1/4 or 3/8 thick) along the angle iron (See image). Along with some spacers and a additional pillow block.

Well like everything it is a work in progress.

 

[rhamer]

When I was a child, I remember the combination of old sprockets and a new chain (or vice versa) on my push bike would always slip for a while under load.

Apparently you are supposed to replace them together and let them wear together.

Are both the chain and pulley new?

Just a thought.

Cheers

Rohan

 

[workinprogress]

Both are new

 

[2manyrocks]

Way cool.

It's odd to me that the bend appears to be outward. I would have thought it would bend inward. Maybe you could weld a cross member between the two sides as a stiffener? You're way ahead of me on this one.

 

[Matt_Jr]

Workinprogress, I noticed your sprocket is not aligned with the chain. The inner portion of the axle is too high (needs more spacing). Is that disconnected there? Also instead of just welding a piece of plate on the angle to thicken it, it would be a whole lot stronger to weld in a gusset there on the top and bottom of the angle too. That would spread the torsional forces along the cross member of the frame(the length of the gusset) instead of just in that one area.

 

[Matt_Jr]

Looking at the last two pictures again, the angle of your axle apears to be the whole problem. I think thats what bent the angle. When the axle was tightend against the inner and outer portion of the frame, that's what twisted your frame. The chain is walking off due to the alignment of the sprocket being off. When you get those little bugs worked out... man that thing looks like fun. And to know you built it, such braggin' right man. Cool project.

 

[Matt_Jr]

Ok, read your last post again, noticed you're gonna put spacers on the pillow block. You were ahead of me. That things gonna be so much fun.

 

[gazoo1]

WOW THAT LOOKS GREAT THIS WOULD BE VERY COOL WITH A SNOW BLADE ON IT WHERE WE LIVE .GOOOD LUCK WITH THE TENSION SOME GOD IDEAS FROM THE GUYS

 

[JoelD]

Work,

Here's my thought, never having built anything like this and never having opperated your machine or ever even having seen it operate (can I be any clearer around my ignorance??)

OK, with that said.

I'm still of the opinion that your problem is likely the entire subframe flexing or some subset there of.

You did mention that she works fine until under stress, if it was the bend (which I don't really think it is, at least by looking at the picture), I'd expect it to walk off all the time.

When my buddy had flying squirells in his attic we could not figure out where they were coming from. We took the mini-bosses video monitor, put it on his roof, hooked it up to his VCR and recorded the roof all night long, sure enough, upon inspection the next morning his wife could see them coming out of the ridge vent, hole plugged, problem solved.

I'd suggest the same with your machine. Video tape it, really good, a couple of times showing the chain walking off, I think that may give you the answer.

Would hate to see you fix and re-fix the wrong problem.

With all that said, I hope your solution works!!!!

I think everyone should own a track machine at least once, I've had two and until you've operated one, that itch is never really scratched.

Good luck my friend and thanks for sharing your terrific project.

Sincerely,
Joel

 

[tlbuser]

I'm wondering why you didn't mount the wheel motors directly to the track avoiding the chain setup? Great project and nice fab job,

 

[larryccf]

first off, i forgot to say earlier - WOW awesome build - color me jealous for sure.

as to the chain, whether the frame is flexing or not i think is irrelevant to your issue as a permanent solution. Frame or bracket flex can introduce the slack that lets the chain come off, but removing that flex will not be a permanent or long term solution - it will simply mean the chain, without a tensioner, will have to be kept tight at all times. It will stretch, and when it's loose enough to come off, it will - that's what chains do. My suggestion is that chain should have a slight bit of slack on the non-pulling side of the sprocket and then a tensioner on that side (or slack side) to keep it taut. That slight slack will help keep the frame flex from stretching the chain prematurely (ie, it will give the chain some ability to respond to the frame flexing forces without having to stretch).

if not, it will stretch, no matter how many times you re-adjust it, and just come off again. And at one point in the stretch, chain will have to be replaced. Leaving some slack, and then a tensioner to take that slack off puts all the "stretching forces" on the pulling side of the sprocket, and minimizes any others.

I built a few motocross bikes and chains in that environment are in pure destructive environment - check in the motorcyle accessory sites for a good tensioner with a nylon block/guide that rides on the slack side

 

[Stampeder]

Work:

This is an awesome project and well designed. I really like the use of hydraulic motors to solve the differential velocity problem. Nice fabrication as well.
I too recommend the idler on the slack side. I have farm equipment and a square baler with a seriously big chain, two actually. It has to deal with serious pressure compacting the hay into a sixty pound bale. Both of them have idlers on the slack side to solve the problem. Neither have any chain guides to prevent it jumping. Oh did I say my baler is over 30 years old and hasn't thrown one of these chains yet. But through a ton of bales though.
Hope this helps.
Really love the way you built the tracks!! Keep the pictures coming.
Glenn.

 

[tommu56]

I think the build is awesome!

When you add the boogies in the middle of the tracks they will take some of the weight off the sprockets and they will only have to pull and not carry all the weight.

tom

 

[workinprogress]

I am heading out into the garage later today to make improvements. I suspect the chain issue is a combination of multiple issues. The sectioned flexed in beginning with but then after more aggressived testing I think the frame bent but was still flexing some. With some heat and a 6ft pipe I was able to straighten the angle iron. When I first mounted the chain up everything appeared to be in line (using a small square). The photos showing the bend show everything out of alignment. The chain always came off the same way: off the lower sprocket and to the inside of the machine. This matches the out of alignment issue that are from the bend. Also the lack of additional guide rollers on the track added stress to this track sprocket and might have also contributed to the bend. The aggressive test I ran went up some pretty steep hills so this would have put most of the machines weight onto the rear sprocket along with high torqure of driving the track. Not to mention I know the machine is rear heavy from how it turns around.

When I get things updated I will send more photos.

A few other items

Idler Sprocket - Everyone seems to say on the slack side but the slack changes sides when you go forward or reverse. I would think most of the time it would need it when the unit goes forward (higer percentage of the time).

Connecting motor directly to the sprocket - The chain drive is currently giving a 3.4 to 1 gear reduction. Not to mention the small size of the track sprockets would put the motor 2-3 inches from the ground. The chain drive is gives me some more clearence. While I may change chain the reduction (2.4 to 1) to make the lower drive sprocket smaller which will gain some clearance and keep it out of the dirt.

 

[larryccf]

"...Idler Sprocket - Everyone seems to say on the slack side but the slack changes sides when you go forward or reverse. I would think most of the time it would need it when the unit goes forward (higer percentage of the time)..."

i hadn't even thought about reverse (didn't have them on motorbikes) but i agree with what you said - going in reverse will be minimal and when you are, doubt the dozer will be seeing the load it is in forward when pushing

as to idler sprocket - you could go that route and it would be better but the tensioners that we used that basically pushed against the chain on the slack side, lasted pretty good while on dirtbikes with no care - they were approx 1" wide by similiar amount thick nylon blocks, maybe 2.5 - 3" long - they'd be easier to fab on, they'd eventually wear a channel in them that also served as a guide

if you do go with idler sprocket, i'd put it on the outside of the chain pushing in - that keeps the chain on more teeth of both of the drive sprockets, so less inclination or ability to jumping off

didn't realize you had a bent frame - (i didn't do a thorough read of the entire thread), but yeah that would have major influence on chain

and you can still color me jealous

 

[Ductape]

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.

 

[JoelD]

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.

That is a really good suggestion, that way could be direct drive, not sure what that would mean to your torque though.

Also, I think in the long run you need to be able to pull as hard as you can push. I think, as you've initially said, it is much about stiffening, with the chain drive, there just can't be any side to side shift between the two sprockets, they can get closer and further appart, but no room for side to side.

Great project and we are all learning.

Joel