Testing videos

Here are some quick videos of testing the controls, with the tank up on blocks, so you can see the tracks spin.

http://www.youtube.com/watch?v=57JHU36DMF4

http://www.youtube.com/watch?v=qVlKSW1p_hM

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Testing

Well I got the wiring all buttoned up.  The issue ended up being the automotive relays got fried (12v relays didn’t like 24v).  I installed some idler pulleys to the drive belts.  And, put the levers in forward, gave it some throttle and….. it moved!!  I was able to go back and forth, and the tracks and drive sprockets, and controls all work great!  I am having some issues of blowing fuses when I get motors under too high of a load, so need to figure out how big of fuses to use without frying my relays.  May have to look for some high amperage relays.  Here is the wiring board with the new 24v relays:

The other thing I figured out is that I stupidly mis-calculated the top speed.  I was assuming a 5.125″ drive sprocket to figure out the speed (just like you would using a wheels diameter/circumference).  The problem with this, is the thickness of the tracks! By the time you add that in, the diameter is closer to 9″, meaning I have almost twice the top speed, and half the torque I was expecting!! So looks like I am going to gear it down 2:1 from the motors to the drive sprocket, and while I am at it, I am just going to switch to chains and sprockets to eliminate belt slipping issues.

Controls and wiring

Well I got the switches in the control box wired, the levers installed, and the whole system all wired ready for testing.  I have a loose wire or the pass-through relays are acting funny, so it is working intermittently, so I am trying to track down the culprit.

 

I also installed the tracks and the drive belts.  While the electronics were working, I tightened them up, to see if the thing would roll!  And… drumroll…..  the belts slipped on the pulleys.  This is either because the pulleys are too slick being made of UHMW, or the belts just aren’t tight enough.  I will first try to just add some idler pulleys to tighten the belts, and hope that works.


Also, the total weight of everything seen, including suspension, tracks, and batteries, is 240 lbs, which I am pretty happy with.  The batteries are probably a good chunk of that weight, but that is how it works with electric vehicles.  Batteries are heavy, or expensive, one of the two.

Chassis assembly

Well I finished painting the lower hull and frame, and put the frame in the wood hull, and everything lines up great.  The pieces I added for the front nose piece look like they will work out nicely.

And then I installed the bogies, rear idler wheels/adjusters, drive sprockets, and the motors/pulleys.  I am test fitting the control levers here also:

Now I am wiring it all up, and everything is just about ready to test the controls.  I will have a whole post about the wiring and testing coming soon.

Even more lower hull and frame work

I glued in some “stringers” to the floor. These are 3/4″ thick pieces of wood, that are the same thickness as the frame tubing so they will be flush. They will help support the interior floor, and will be used to attach some interior stuff to, rather than drilling and bolting everything to the frame.

I began painting the inside white with a tough latex paint. Going to be a few coats to have a nice sealed finish:

I also welded on the supports to the frame for the track fenders, as well as some tubing to help support the upper hull later. Then after some sanding of surface rust, gave it a coat of primer.

Lower hull almost done

I finally finished fiberglassing all of the outside surfaces of the lower hull. Stopped and sanded a few times, before adding more cloth/resin, to keep everything fairly smooth. Definitely not a perfect job, but most of this won’t be visible, I just wanted it nice and waterproof. Then I primed it with self-etching primer, then sprayed a coat of green. Still need to do a little more on the first coat (ran out of paint), and then spray another coat. Then I will be ready to flip it over and paint the inside, and get it all ready to mate it back up with the frame.

 

It’s always nice to see stuff in it’s final color!