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The world as we know it is destroyed. All that's left is the wastelands of a civilization that once thrived. But for us who have survived the fall of humanity, we need a vehicle that can bring us to safety - and help everyone else do so.

It is the Halftracker.

This is my submission for the TC17 contest. As the name suggests, it is a half-track. It will have a claw arm attached to the roof of the truck. The arm will have full 360 degrees of rotational freedom, but unfortunately this means only two functions can go through the turntable. The functions/features I am considering for this model are:

  • Driven tracks (uses an individual L motor on each track as opposed to a differential to prevent slipping)
  • Steering on front axle
  • Oscillating front axle (with shock absorbers)
  • Suspended tracks
  • Arm rotation (full 360 degrees)
  • Jib elevation
  • Claw
  • Additional motorized function (e.g. a winch). It will have 3 IR receivers, so there is room for one more function.

The suspended tracks and oscillating axle will help the Halftracker tackle any fallen debris, and the claw arm will clear out any roadblocks for people to get through.

Currently I have the tracks and their drivetrain and the front axle (the oscillating portion) completed. The tracks are pretty solid at this point, so building the chassis should be pretty straightforward.

Photos:

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Edited by JLiu15

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I see one big Moc coming...and to make both wheel and tracks drive it takes something extra brainstorming... looking forward to see how it develops.

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1 hour ago, I_Igor said:

I see one big Moc coming...and to make both wheel and tracks drive it takes something extra brainstorming... looking forward to see how it develops.

Oh no the front axle won’t be driven - it’s just steered and suspended. It would be really hard to get the gear ratios just right lol.

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37 minutes ago, JLiu15 said:

It would be really hard to get the gear ratios just right lol.

I know that from your description in first post. I was just "justifying" your decision because I have spent more than half a year for that kind of solution and manual version works with 4 differentials (one for wheels; two - each one for one track and one central) but when it is motorized it does not work...so I'm looking forward to see how your chassis structure will be, perhaps you could give some idea for my project. :classic:

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5 hours ago, I_Igor said:

I know that from your description in first post. I was just "justifying" your decision because I have spent more than half a year for that kind of solution and manual version works with 4 differentials (one for wheels; two - each one for one track and one central) but when it is motorized it does not work...so I'm looking forward to see how your chassis structure will be, perhaps you could give some idea for my project. :classic:

The most difficult part of the chassis I think will be where the oscillating front axle is, as there is not much room for reinforcement in an area that especially needs reinforcement.

Edited by JLiu15

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1 minute ago, JLiu15 said:

The most difficult part of the chassis I think will be where the oscillating front axle is, as there is not much room for reinforcement in an area that especially needs reinforcement.

I know that, that is what I'm looking forward to see how you are trying to make it work. As I already said (wrote) perhaps you can give me an idea...

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2 hours ago, I_Igor said:

I know that, that is what I'm looking forward to see how you are trying to make it work. As I already said (wrote) perhaps you can give me an idea...

I’ll be updating the topic over the next few days, showing how the build progresses. I’m planning on finishing most of this model before I go back to college next week.
 

Glad you are interested in my MOC!

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Very nice idea for this theme! :-)

On 1/12/2020 at 3:40 AM, JLiu15 said:
  • Driven tracks (uses an individual L motor on each track as opposed to a differential to prevent slipping)
  • Steering on front axle

I think it will be really challenging if you use two L-Motors. IMHO the first half tracks used a diff on the driven tracks, just later ones really adapt the speeds directly according to the steering angle of the front wheels. There are even some (like the Kettenkrad) that breaks one or the other track according to the steering. Damn, I really should built a Kettenkrad for the TC17 xD

Edit: Or you use this :-P

Edited by Jundis

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16 hours ago, Jundis said:

Very nice idea for this theme! :-)

I think it will be really challenging if you use two L-Motors. IMHO the first half tracks used a diff on the driven tracks, just later ones really adapt the speeds directly according to the steering angle of the front wheels. There are even some (like the Kettenkrad) that breaks one or the other track according to the steering. Damn, I really should built a Kettenkrad for the TC17 xD

Edit: Or you use this :-P

My Fire Rescue Half-Track from 2016 used a differential on the tracks, and it suffered significantly from slipping. The hard plastic tracks are a lot less “sticky” than rubber tires, so it doesn’t take much for a track to lose contact with the ground and thus strand the vehicle.

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UPDATE 1/14/20

The chassis above the tracks and the front oscillating axle are done. I've just got to join these parts and add the motors and support structure for the arm, and I'll be finished with the chassis.

I was anticipating the part above the front axle to be challenging due to the lack of space for reinforcement, but it actually turned out pretty well and it's very structurally sound. However, due to the height of it I'm probably gonna have to add another set of parallel beams to reinforce it to the chassis, probably to the support structure for the arm.

The part above the tracks was actually more difficult than anticipated. Sure it's just another set of parallel beams, but I had a harder time finding a way to reinforce this than the part above the front axle. It ended up with plenty of reinforcement, though.

Photos:

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33 minutes ago, TechnicRCRacer said:

This thread is exciting to follow, keep up the good work!

Thank you! I’m glad you like it.

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I think you can use pair of 11 x 5 frames (placed vertically on each side) to make stiffer construction carrying tracks

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3 hours ago, I_Igor said:

I think you can use pair of 11 x 5 frames (placed vertically on each side) to make stiffer construction carrying tracks

I’ll probably do something like that for the support structure of the arm. The chassis immediately below it is gonna need quite a bit of reinforcement.

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Hmm.. Are those springs at a state of constant compression? Because when the other spring compresses as the suspension tilts to the side, the other spring would stretch.. Or do you have a some kind of mechanism that lets the spring stretch?

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4 hours ago, Mechbuilds said:

Hmm.. Are those springs at a state of constant compression? Because when the other spring compresses as the suspension tilts to the side, the other spring would stretch.. Or do you have a some kind of mechanism that lets the spring stretch?

Both shock absorbers are about halfway compressed. And yes, when the suspension tilts to the side, one spring is fully compressed while the other one is fully decompressed.

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UPDATE 1/17/19

The entire chassis is now finished. I finished it late last night, and took the photos before I went to bed. The chassis came together pretty cohesively - the motors for the arm functions fit perfectly between the tracks, and directing their drive up the arm's support structure was pretty straightforward. The arm rotation motor fit perfectly inside the support structure, between the drive axles for the arm functions. The arm functions and rotation are all driven by PF M motors.

The power supply of the model is a PF rechargeable battery, and it's placed just in front of the arm's support structure. The IR receivers are mounted behind the support structure, and overall wire management was pretty easy. I did have to stack the plugs of the IR receivers elsewhere though - there is simply not enough room to stack them on the battery box. The stack of plugs is quite an eyesore, but it should be covered up pretty well when the body is built.

Note that the turntable for the arm isn't installed yet - the turntable will be supported by the body elements, so I'll add that when I get to building the body.

Photos:

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Edited by JLiu15

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UPDATE 1/20/20

Not much since the previous update, but I've added a fake V6 engine as an additional feature. The engine is driven by a PF M motor located directly beneath it.

I went all out decorating the engine here. It's been given a heavily modified appearance, and it will be exposed and stick through the hood. I added the engine because while planning out the bodywork the hood just looked bland. I wanted something to really make it look aggressive, and to really give it that Mad Max feel. Overall, I'm pretty satisfied with how it turned out.

Some other changes I've made to it since the previous update are that I moved the stack of plugs for the IR receivers towards the back, below where the bed will be installed so they'll be completely hidden. I also removed the side panels on the tracks - I just felt like they didn't belong there.

With a heavily modified V6 engine under through the hood, The Halftracker proves that there's no obstacle it can't power through.

Photos:

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