OK, here is the concept drawings of the 2-4 Man Sherman Walking Tank.
The first thing you need to understand is that this design WON'T WORK!
Do not attempt to build it... Many, Many problems with this design worth discussing here...
As ALWAYS weight is the primary issue. You can't read those yellow boxes but they are my calculations of weight of the components. It came in about 60 -70 pounds PER person in a 4 man tank config. More with 2 person. Wheels or not, would you want to push, drag or carry that all day long up and down hills and over logs and rocks? maybe... The 4 man config was about 10 feet long and 5 feet wide.
Had a 4" hollow core PVC pipe frame with schedule 20 fittings. PVC is just plain heavy. Tried 3", 2" and those came out even heavier as you built more reinforcement and used more fittings. I have seen 3 PVC frame paintball tanks and everyone BROKE the first day of play... All PVC framing with netting. I supposed adding that twin wall to the sides would make is much stronger but I still had my doubts and when I added up the weight, REALLY has second thoughts. When you break PVC, you can't really repair it short of fiberglass and epoxy which means you are out of play if it breaks.
Note the small caster wheels in the front and large 26" mountain bike wheels in the back. HUGE MISTAKE with that design. Just like a grocery cart. Just go borrow one at your local grocery store, fill it up with groceries and try to drive it on the grass or over gravel. Won't happen...
A guy that TRIED that configuration told me not to do it saying simply, "There was a reason the Romans put the horses in Front of the Wheels on a chariot." You think about it and you would be pushing this design around BACKWARDS all day long if you could push it at all.
Don't make it a PUSHER walking tank. The guys inside are the horses and they need to PULL it around the field. I'd put waist 'harnesses' on them too just to free up both hands most of the time if they don't have to lift it up over obstacles, turn and such. Of course you need a place to store your marker while you are maneuvering. A gun sling or shelf or something.
In the plan, I wanted to use 3/8-1/2 plywood to mount the bicycle axles into. Some big pan washers and still concerned about breaking them out of the wood. Decided to 'sandwich' the axle between two piece mounted on each side of the PVC framing. Rather than using screws that would weaken the PVC, just clamp them on. Then I could also slide the axles forwards and backwards to get the Center of Gravity of the tank where I want it relative to the axles for the easiest pushing/pulling. Once tweaked, maybe fiberglass the plywood to the PVC frame. Something simular for the front casters. They would have to be VERY Beefy since they would be jammed hard into hundreds of obstacles a day. Couldn't come up with any good set up and anything close was getting heavier and heavier and heavier trying to build it strong enough not to break. The wheels and their mounts were coming in at 25-35 pounds or more.
If you have 4 wheels and are on a hill, and want both hands free to shoot your marker or the cannon, wouldn't it ROLL? Duh! Do I need brakes too? maybe not very far with the waist harnesses.
The turret was framing and all netting for visibility and air circulation. It was suspended from above and would turn 360 if the barrel was short enough. It would have to be perfectly balanced with the cannon in the front and the air supply in the back counterbalancing the cannon. Multiple gun ports in the netting to shoot out of regardless of what position the cannon was in. If the cannon was being moved, port gunners would have to suspend fire until it stopped. Didn't like that and decided I would still have side, front, and rear gun ports in the body.
Body was PVC and that polycarbonate twin wall for the 'armor'.
There was a hanging door hinge in the back that is what you would use to enter and exit the tank. I wanted to be able to drop a player to complete a mission such as raise a flag, retrieve a prop, plant a satchel charge, rescue a pilot, occupy an objective, etc. Things they wouldn't let a tank do without someone exiting the vehicle.
So it was a defective design in a LOT of ways. Figuring out what won't work is helpful figuring out what will work. Plus a little out of the box logic.
The wheels and mounts weigh 30 pounds. Would be nice to get rid of them. How? Lighter wheels? Smaller wheels? Roller blade wheels all along the bottom might work. How much would they weigh? Would that spread out the stresses enough to have lighter wheel mounts. Weighed some stuff and did the math. Not much gain if any.
How to get rid of the wheels and framing gave me the first thought of a backpack based walking tank as a possible solution. Watching a rerun of
star Wars with Chewie coming up in that captured ATST and a HUGE light bulb went off in my head...
Could I use something other than that HEAVY PVC pipe and fittings. Wood? Plastic? Metal? They used to make biplane wings out of wood, glue, and fabric and then flew them in loops in WW-I. Strong and light. A matrix of wood might be lighter. Lots of fabrication time but maybe not if you used jigs and modules and such. Looked up how they made those wings. Definately a lot of fabrication time.
So I parked the idea. Went with the one man - mech warrior walking tank.
Came across that polycarbonate and decided to run with it.
Now with my second Mech Warrior tank using that mono body concept where the polycarbonate IS the structural material that allowed me to eliminate an internal frame, It has proved quite sturdy and durable.
So my thoughts return to this 4 man design. It might drop over a hundred pounds of PVC pipe and fittings. You could make a 8' long, 4' tall, 4' wide open bottomed box out of Four 4x8 Sheets of that twin wall. 35 -45 pounds with the corner profiles and glue. JESUS! One guy could drag that around all day. Did I say "Drag"? No wheels and you would BE Dragging it. OK forget the wheels and make a SLED that looks like a tank. The 'runners' would look like tank tracks. Started guesstimating weights and gear and this 2-4 man concept was a WHOLE NEW ball game. Certainly wouldn't need brakes on a sled. How to make the whole thing out of polycarbonate using a mono body building concept. Tank tracks 7-8 foot long that were 6-8 inches wide would be an long, empty box with some cross reinforcement inside where they are attached to the box/body of the tank. Overlapping 12-18 inches at the attachments. Swinging/hanging door(s) front and back for entering and exiting but also reducing the amount of ground clearance needed for the body. They would just swing up as your walk over tree stumps and rocks. Net turret again - minimal weight until you start mounting cannons and air supply.
Then how do you keep the bottom of that polycarbonate track from grinding and banging holes in it? Multiple layers. 2 would last longer but you would still have some severe wear and tear. We have a 12 year old OLD TOWN canoe that has been dragged over every gravel bar on the float streams in here in Missouri. It has a Kevlar and epoxy protector on the keel that had worn off and I needed to replace it with some new Kevlar. The Kits run $70 so I just order some Kevlar forearm protectors for sheet metal and glass workers for $5 each and used them. Another light bulb goes off. Just epoxy Kevlar to the polycarbonate and when it grinds off, just slap on another layer of kevlar and epoxy. Low maintainence, low cost, and field fixable at a game if needed. Sure wouldn't be a mud collector like wheels would be.
Then I got my ZTR mower to cut grass and make my first motorized tank.
Again a one man but motorized. This design would make a decent shell for a motorized tank. No wheels needed. The monobody would make it easy to pop off the tank shell and convert back to mowing grass until the next game. Make the shell and armorment all self contained for the ease of the converstion.
Then a thought came to me. There is a good chance some producer might actually ASK to see the paintball tank insurance policy I don't plan to purchase. If I designed it right and self contained, I could just pop the shell off and use it as a walking tank. No insurance required. Ditto if I have a mechanical breakdown. I could still play as a walking tank. Seems like a viable idea at this point.
So that sled, motorized and/or walking tank is back on the drawing board this winter.