Before finally installing everything, I laid out the pulleys their approximate relative distances they would be from each other once installed, to verify the idler position and where it will need to swing to tighten the belts enough to engage the pulleys on the track drive sprockets. From this angle you can see how moving the idler up would fully engage the brown belt (reverse spinning), down would engage the green belt (forward spinning).
It also became evident once I laid this out, that moving the idler forward or backwards (left or right in the picture) will loosen or tighten the belts at the idler rest position. Good to know when I make and position the idler actuator arm later.
I began assembling the transmission drive shafts. These are 3/4 solid steel rods, which I will need to cut a few grooves into for the pulleys keyways/set screws. So far everything is looking like it is gonna fit and align perfectly. One will be constantly sipping in forward, and the other in reverse when the motor is running. There is no sort of clutches or anything.
Here are both of the shafts. Once installed one will be right below the other one, and the pillow block bearings will bolt to the frame with the same bolts.
I will weld in some mounting plates to bolt the bearing’s to the frame, since the holes would weaken that 3/4″ tube too much. The white pulleys on the track drive sprockets are just set in place to show basic alignment.
Well, here goes. Taking the tank apart, pulling the electric motors, and swapping in a gas engine with a idler engaged pulley style transmission. I’m tired of the 1hp from the electric motors, and not being able to have the tank really drive anywhere fun. Will probably go with a 3 to 6 hp engine in the back, and transmission in the front.
Here’s the basic plan for the transmission. The motor spins 2 shafts in opposite directions. Each has a pully on each side, which can be engaged with an idler, giving the 4 options: Left Forward, Left Reverse, Right Forward, Right Reverse.
To turn the 2 shafts in opposite directions, the current plan is to have the chain wrap around a sprocket on each shaft, and an idler to give the proper clearance.
The other option is to drive one shaft with the motor, and have it drive the other shaft in reverse via cogs/gears. But I’m leaning toward the chain method.
Thanks to the Oregon Veterans Home for letting us bring the tank there! We brought it for some of the residents to take a look at it, ask questions, have their picture taken with it, and watch my son drive it a little. We had a great time, the residents seemed to enjoy it, and the staff was really great. I also brought a display of pictures of the build process, most of which were pulled straight from this blog. Here are a few pictures of the great day we had there.
This was my son’s first chance to really drive the tank by himself, with the turret on, in an area big enough to go for a while with nothing to run into. He had a great time. The tank did pretty good.. nothing broke, and the suspension and controls all worked fine. Just need some more HP at some point, it struggles turning in place on soft terrain, and going up steel inclines.
Here is the tank getting some more testing done, and a new driver trying it out…