He is at it again! 1:50 Dozer Conversion

[john]

An yes stall current is when the motor is stopped as most are a dead short. But I honestly do not know about brushed an brushless. We're they stalling? Or would they spin the track? The power to wieght ratio is a fine line but I believe if the tracks would start to spin before the stalled out it would be easier or less harmful on the electronics.

[SmallHaul]

Originally Posted by john

small haul thats the drive sprocket? you beveled the teeth on it it looks like? on both sides or just one side of the sprocket? so does that push dirt out or crunch it? good idea

Thanks, yes i just cut the back side so that you can't tell just looking at the machine. It works very nice, even if you get dirt in the tracks you just have to travel back and forth a couple of times and it chews and pushes the dirt out. Knock on wood i haven't had to manually removed dirt from the tracks since i did this mod.

[john]

easy maintainance i like!!

[Rvjimd]

Getting closer now. Really need the no brake ESC's to get this thing smoother and easier to control.

Pu t the high power motors back in and geared the final drives down to 15:27. I am also using 2 cell 850 lipos in the video. I have tried 3 cell but I think the motors just turn too fast for the gearing I have installed.

The gear motors are 298:1 with a torque at 6v of about 70in oz.

http://youtu.be/hshpCtwx9x0

Still need an operator! I have now beveled the drive sprockets, hope that reduces the dirt clod interference and jamming.

Jim

[Rvjimd]

One more quick video. I almost have this little thing working! Got the new speed controllers today. Wow, that works better! No more double clutching!

My trouble is the little tiny gear motors keep slipping on the final shaft and the last gear and then the pinnion gear on the output stops.

Guess I'm going to have to look for some other motors in a bit bigger size, but not too much.

http://youtu.be/sUAG0wC4Xz0

Jim

[john]

Looks great Jim! So the tracks were jamming more so in reverse? Did bevelling the drive sprockets help? I still total amazed that there is a battery in there somewhere haha. As for an operator I received a book from the collectors guild yesterday they have a few people for doloramas an stuff or have you tryed that 1000 toys.com?

[Rvjimd]

Thanks John,

I haven't had enough run time without a gearbox failure to tell how the beveled sprockets are working. I don't see how it won't help some? They way I figure it, there is less surface are and volume of the tooth of the sprocket to poke down into a link in the track chain with them beveled. So if a piece of dirt or sand or whatever is in a link, maybe the pointed/sharpened cog will ride past or cut the debris as it turns through the link?

Only downside I see could be that the tracks can now float outboard a bit due to the reduced width of the teeth.

I haven't really started looking for operators yet. I keep hoping I might find something local at a toy store. Might need to get online and order some.


Jim

[Rvjimd]

I made some more changes and adjustments and the dozer is starting to work real good now! Found an operator at wal mart! Got to love the eye patch!

http://youtu.be/0nWYDhsPwdQ

Jim

[modelman]

Jim-to me the dozer is a little too fast for realistic operation but it looks like it works really well. Also the blade up and down is faster than normal but this is due to the way it is rigged with the servo. This is just my opinion and you did a great job on the conversion. My main goal has always been realistic operation so this is the first thing I look at on any type of working model. Good job!!

[Rvjimd]

Tom,

I agree on both counts. I plan to run this way for a few hours and try to tune them down and see if it still pushes good. I get mush better and more realistic look when I get up close and go slow. I really need to be able to see the bottom of the blade to keep good control.

I'm having a blast with it! About time to go back to the pond with it and find a good realisting "job" for it.

Jim

[modelman]

Jim-I can see that it is a bit tricky to run smooth with the blade and tracks moving that fast but looks like you are getting good with it. Practice always helps. It looks like a fun machine to operate and when you get it out in your working pit I'm sure it will fit in nicely.

[john]

Tracks are clearing perfectly! Great job! Do you have any pics of how you squeezed the batteries in there? They seem to last decent time an even spins track an still pushes fair bit eh! lol are you going to put winch back on?

[Rvjimd]

John,

The batteries actually fit pretty easily. In the last couple videos I have been using a two 850 two cell lipo packs. They fit side by side under the hood, and I plug them in and bunch up the wires and slide the hood onto the chassis. They seem to last really great! I have not done a real good check, but I know they would make 30 minutes for sure! The little motors and standard servo of the blade don't task the two batteries too much. I do notice that the battery running the servo is always a bit lower voltage than the other.

I need to adjust the right side drive train, so I'll try to get some more video of some of the different detail.

As for the winch, when did you see a winch? Did I take a winch off of it? the little 1:50 AC did have a ripper on it, but don't be confused by me switching dozers and scales mid conversion.

Jim

[Rvjimd]

Making a new aft chassis for the dozer. I already had the larger spur and smaller pinion sets so since Tom thought I was too fast (he always seems to be right about this stuff!) I decided to do a little refit. I'm just guessing at the ratios. It ought to be close, and even if it comes out too slow, that would be good anyway! Then I can order a couple new motors geared a bit faster with a lower stall value to protect everything.

With any luck this will all turn out perfect, have great performance and I'll have it running by 2pm today!

Oh, and thinking out loud here, I realize that without seeing this thing up close it will be hard to picture, but..

I need to figure out how to add a bit of tension to the tracks now. The pins cast on the links are starting to wear a bit and they are just a bit too loose now. Don't want them to get tight, but they are too loose they way they are now. The spring at the front idler wheel is not looking like a good solution.

http://youtu.be/DzCHNof5Pu8

Jim

[john]

Oh my mistake Jim sorry i had winch on my mind for added weight for traction, wow thats alot of bevel on the drive sprockets!! as for track tension is there room to add a set screw to look front idler from moving back an loosening tracks? you would have to adjust it once in a while, our old ac had a huge wrench to turn a thread that put more tension on and my case uses a piston afew shoots of grease from a grease gun and shes tight, but i really believe your limited for space ill keep thinking tho, im assuming your hoping for automatic adjustment?

[Rvjimd]

Started working on the track upgrade yesterday. I'm drilling out the cast pins and thru both part. Then 1/16" piano wire goes in place. The two pictures show the slop due to wear of the pins cast on the original pads. I was able to remove a complete link and get the track back on, it was too tight though and I didn't run it that way.





The short top section is what I have done so far, just started.

Jim

[SmallHaul]

Its nice there is enough metal on the links to add pins... How much running did it take for the tracks to get loose? Are the drive wheels holding up ok?

[Rvjimd]

I'm not totally sure about the time but I estimate 4 or 5 hours. The nubs cast on the inner part poked into the hole of the outer tread in front of it. They were never that tight to start with.

Jim

[Rvjimd]

What/where should I look for roller chain with mounting tabs for building tracks if it comes to that?

If I understand and measured correctly, the original tracks measure 3/8" pin to pin. And 1/8" wide inside.

Jim

[Espeefan]

Jim, glad to see you are still working on this project. It's pretty amazing what you've been able to accomplish with such a small model. Those little motors sure sound strong and the dozer seems to have some good power, despite the small size. Very impressive.