Steamer

[steamer]

789C is finally cosmetically finished. Just need to build the radio rack and do some more work on the hydraulic cylinders and she's ready to haul dirt.



I have to modify the lift cylinders because the tolerances were too tight and won't come back down properly. I think if I change from o rings to cup seals it should work better.
Thanks for looking
Rob

[Espeefan]

That looks really nice! Way better then the Tamiya Mammoth it started out as. Nice job.

[RCP57]

Looks sweet Rob! Hopefully I will get to see it soon!

[RCLogger]

The frame looks good with that fresh paint. Looking forward to getting it dirty.

Greg

[Old Guy]

Rob

I had the same problem witn my telescoping cylinders I found the solution was to add a ring just above the piston seal about 1/2" wide this eliminated the binding problem. I was lucky with the rear dump as I had more stroke than I needed and could add the 2 1/2" stops
Hope this helps.
Earl

[steamer]

Earl. thanks for the great suggestion. When I get back on the project I'll give that a try. I also thought about putting in return springs on the piston rods inside the cylinder. There's lots of room inside and more power from the pumps than needed to lift the body full of dirt. I'm hoping that the spring action will start them down.
Thanks Rob

[Old Guy]

Rob
Like you I was getting frustrate with the slow down on the 2 stage cylinders on my rear dump, so I fixed it Ij ust reverse the hydraulic pump it comes down as fast as it goes up, I could do this as the pump I built and I knew I could reverse it and the pump is only connected to the lift cylinders, just a thought

Earl

[steamer]

I'm using Wedico pumps on this one and they're designed to run both ways forward and reverse. My problem is when the cylinders are full stroke the pumps pull all the oil out and create a vacuum. You can imagine what happens then, the box slams all the way to the bottom because there's no oil cushion left in the cylinders. I thinking with the internal springs there should be enough return pressure to start the box down when the pump reverses. At least that's what I'm hoping for.
Rob

[RCP57]

So Rob, Are you coming to Duncan or what?

[steamer]

Well, with everyone posting Bruder conversions I thought that I'd throw mine in here. I took a different route and went with regular gear motors for the tracks.


The shafts on the motors aren't long enought to get through the track housing so i extended it with some couplings.


Turns out that the center of the drive sproket after checking it with drill bits is 4mm so I drilled through and fastened a hub to the outside of the sproket with screws and it worked fine.



Hooked a Saber tooth to the motors and It was moving quite well. Next up is the cylinders.
Thanks for looking.
Rob

[RCTech9]

Nice work Rob! Are the tracks Steel?

[RCP57]

Looking good Rob! It's about time you posted some pictures. You checked your email lately?

[steamer]

The tracks are the plastic ones that came with model. If they don't last I'm hoping that someone will have replacement ones available then. Reg, That four stroke engine is a thing of beauty and looks to have a lot of torque, just the way I like em!

[RCP57]

Haha nice! I find you can never learn enough about mechanics....We can both thank Mario for the literature....

[Lil Giants]

So how did the problem solving go with your dump trk cyls Rob? We have yet to see a vid of your reworked Mammoth.

[steamer]

Still having problems with the cylinders not retracting. I think I found the soloution this morning thou, with a company in CA. They have piston cup seals that start at 3/8" so I ordered some 3/8 and 3/4 that should be here in a coupe of weeks. Have replumed out all the Hydraluic lines with bigger size tubing too, so I have more oil flow. I guess time will tell if it works out or not.
Rob

http://www.allsealsinc.com/ukp.html

[rc_farmer]

I have trouble with only only side running off....still way too much slack in both of them. Hopefully someone will make some stronger replacememts

[Wiskybilt]

Just finished reading this thread. Lots of cool building. I hope you get your seals straightened out. Anything I can help you with on the jacks?

[RCLogger]

Hey Rob
Just looking for some photos from the project you are working on ! I am sure you must have an update . . .

Greg

[RCP57]

Sounds like he has been working on a bunch of stuff that he isn't sharing....