Axial Land Cruiser Half-Track

[imthatguy]

Tank.



Borked Tank.






Yes, it's true. And a real thing. Changing this to be mechanically accurate too.



Progress has been made.

Step one was to remove the motor and gear assemblies and execute the ugliest part of this build. Fitting an axle (with Axial diff installed) into the area where the driveshafts for the drive wheels exited the chassis. It looks pretty, um, bad, but all will be hidden and works perfectly and securely.




I took the original output shafts, cut and drilled them to accept a couple of cut Axial driveshafts from a rear axle. A little brazing later and we've got the proper outputs for the drivewheels!



At first, I was very concerned that there weren't going to be any lockouts to hold the drive wheels in place, but because of the design of a tank track, they're kept firmly in place by friction and tension in the sprockets and center channel of the helper wheels. If it gets out of shape, I'll come up with some other solution on the axle end to keep the shafts in place in the diff. All seems to be working exactly as I wanted so far.

Also managed to hack up the rest of the body.

[imthatguy]

So, what we needed to do in order to not make this a land yacht, was reduce the overall length of the tracked section. If you look back at the references, the tracks were about 5 guide wheels long. So... Major cutting and sweating resulted in this:



Thankfully, my cuts were (mostly) straight and styrene glue works! Obviously, I will reinforce the joints and fill in the gaps, but cosmetic stuff like that is less important right now. I had to remove 20 track sections, and may remove another one or two more depending on how much tension I'll ultimately need.



That length looks a little more appropriate, no?

[2003EDGE]

Hmmm, that's a new one! Sub'd!


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[imthatguy]

My wallet complained that I bought a brand new tank and didn't even take it outside before completely destroying it. Oh well.

SO! Some minor updates, first and foremost, I found an Australian replacement for these plastic, horrible wheels.



These blokes make metal wheels with actual rubber outers which should help with longevity of the tracked half of this build. Crikey mate, chuffed.

Spent a better part of today working on the cab. There's many changes that need to be made in order to be accurate. First, as Shannwah discovered in his build-off, you've got to do a lot of filling on the roof to make the angle match again.




After joining the bits back together with MEK, I laid a bunch of styrene strips down, then covered that with Tamiya 2-part Epoxy putty. Many hours will pass and then I'll sand it down smooth. Traditional cab-only Cruisers didn't have doors or hatches on the back, they were all solid, so I sanded off the hinges and started filling the gaps. Once the roof is finished, I'll seal up the rest of the gaps and add the fuel filler dimple.




Sealed up the hole I created by adding the axle internals, and tried to keep faithful to some of the lines of the tank.



Getting a feel for wheelbase, and where the chassis will need to sit. I'll be using the GCM forward motor mount kit and a transfer case. I want to make sure that there's a lot of weight over the front wheel to help aid in steering. It's going to be pretty heavy in the rear end, so anything I can do to get more weight up front is helpful. Need to wait on an axle housing (how is it I don't have one sitting around???) before I can set up the front geometry and body mounting to frame.

[imthatguy]

My new metal tank wheels arrived from downunder and I'm in the process of putting those on. They're really nice! Bearings make it run better, but the extra weight definitely puts stress on the driveline. I may have to do some re-engineering later on once I test it under it's own power.



As you can see, the Axial frame is now tied into the tank tracks. I made sure to measure a number of times and figure I've got just the right wheelbase. Of 21 inches. Ha!



Power is run through a captured bearing piece from the RC4WD D110, a couple additional bearings, and an extra shaft from a GCM transfer case. Two driveshafts mated work quite well. All is smooth and firmly in place. Since that power is running through a unlocked differential, I'm not overly concerned about stress, and we'll see how it operates shortly.



Figure I'll need to use these 1.55 Stompers that I've got, wheel there is probably the go-to, seeing as it's a proper Toyota Steelie.



Spent the rest of the evening cutting up a perfectly good interior to fit my reduced cab. Now to figure out the front axle (leaf sprung???) and get some electrics wired up!

[imthatguy]

Front axle mounted, courtesy of some links I had sitting around, GCM's panhard mount, Vanquish steering and c-hubs, and a bunch of LockedupRC internals. Namely, the Heavyweight F1 spool, and OTVD axle shafts. Oh, and extra Beef in the form of BeefTubes. It's a heavy axle, on purpose.




I've over-driven the rear, 36/14 through a 1:1 transfer case, and the front axle is under-driven, 43/13 and it's currently spinning one full rotation at the driveshaft for every 2 full rotations at the transfer case.

So um, can somebody help me with some math? Chris at GCM has already agreed to help me come up with a driveline solution if I can get the numbers right.

And for those of you curious about how it all is looking:

[imthatguy]

So after much noodling and telephone discussions with Chris from GCM, we were finally able to figure out the ratios for getting these ridiculous tracks to turn at the same time as the Axial front end, and in the end, he helped create this one-off custom transfer case:



This brilliant little transfer case gives me the additional spins that I needed to get the rear tracks fast enough to keep up with the front axle. Hooray for ingenuity and prototyping, and Shapeways! I'm excited to get back on this!

[EeePee]

Neat!

Almost as cool as the new F1 cars.

[DeeJay73]

I like!!!!


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[D440]

Nice! How are u holding that super long rear drive shaft?

D440

[Rickleo]

This is what you call rc engineering. Great work my friend.

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[Mike Flea]

Wow, this is a great project, I'm liking the ingenuity , but you may find out during testing, that it will drive better with the drive sprockets at the front of the tracks.

Your primary direction will be forward. As the track drives, it will stay taught on top, in the forward direction, with the slack towards the bottom. That slack will be taken up by the lower bogies, and aid in your turns by not slipping or throwing the track. When reversing, you generally move slower, so throwing a track in reverse is often not common.

The way you have it set up now, the possibility exists to throw a track while moving at a higher speed than reverse. Two things can happen. One, if the track has enough slack, you'll get track-slap on your body/fenders, and two, a greater chance of throwing a track.

I worked on tracked vehicles in the Army, so I have a little experience, and if you look at the prototype, its drive sprockets are up front too.
1:1 Tanks usually have rear drive sprockets because the engine is in the rear, Self-propelled artillery has front drive sprockets because the engine is in the front.

[imthatguy]

Originally Posted by EeePee

Neat!

Almost as cool as the new F1 cars.

Almost, but certainly slower.

Originally Posted by DeeJay73

I like!!!!


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Thanks!

Originally Posted by D440

Nice! How are u holding that super long rear drive shaft?

D440

It's not super long. It's two driveshafts with a captured bearing - to avoid a long driveshaft.

Originally Posted by Rickleo

This is what you call rc engineering. Great work my friend.

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Cheers!

Originally Posted by Mike Flea

Wow, this is a great project, I'm liking the ingenuity , but you may find out during testing, that it will drive better with the drive sprockets at the front of the tracks.

Your primary direction will be forward. As the track drives, it will stay taught on top, in the forward direction, with the slack towards the bottom. That slack will be taken up by the lower bogies, and aid in your turns by not slipping or throwing the track. When reversing, you generally move slower, so throwing a track in reverse is often not common.

The way you have it set up now, the possibility exists to throw a track while moving at a higher speed than reverse. Two things can happen. One, if the track has enough slack, you'll get track-slap on your body/fenders, and two, a greater chance of throwing a track.

I worked on tracked vehicles in the Army, so I have a little experience, and if you look at the prototype, its drive sprockets are up front too.
1:1 Tanks usually have rear drive sprockets because the engine is in the rear, Self-propelled artillery has front drive sprockets because the engine is in the front.

Mike, this is extremely helpful information! Thanks very much for posting! I'm hoping that the front axle will still do a fair amount of the effort to pull the truck forward. I too imagine that real-world engineering would have ben the better way to make this work, but, because I'm using a differential to power the rear axle, I'm hoping to eliminate the majority of track slap. I'm also going to be integrating a spring loaded track guard to keep everything in place in the case that there's horizontal movement in the tracks due to too much speed.

Rear end is looking like a Toyota-ish...

[D440]

Can you show better that captured bearing that holds the union between drive shafts? It's holding well?

Congratulations! Nice project

D440

[imthatguy]

Originally Posted by D440

Can you show better that captured bearing that holds the union between drive shafts? It's holding well?

Congratulations! Nice project

D440

It's the piece in this photo here:

[Highmark]

This is the weirdest and best thing I've seen lately and I think I'm in love.

[BigSki]

I had given a bit of thought to how one would get tracks and a tiny round tire to rotate at the same speed. I came up with the notion that the track is nothing more than a really big round tire that has been squished into an oblong shape. I'm guessing that you would need to know the circumference of the tracks and the circumference of the tire and figure out what the % of difference between those two things are, then work out the gear ratio math to make it run right. The rear end would need to be 'X'% over driven so that one revolution of the tank track = one revolution of the tire up front.

Obviously, GMC has come up with a solution so I'm curious as to how they came up with a ratio for the t-case, and more importantly- does it work?

[snapon boy]

Over the top as always on sbg

149 r/c worx /scalerfab Team Driver

[jebster]

Originally Posted by BigSki

I had given a bit of thought to how one would get tracks and a tiny round tire to rotate at the same speed. I came up with the notion that the track is nothing more than a really big round tire that has been squished into an oblong shape. I'm guessing that you would need to know the circumference of the tracks and the circumference of the tire and figure out what the % of difference between those two things are, then work out the gear ratio math to make it run right. The rear end would need to be 'X'% over driven so that one revolution of the tank track = one revolution of the tire up front.

Obviously, GMC has come up with a solution so I'm curious as to how they came up with a ratio for the t-case, and more importantly- does it work?

Your on the right track. You need to determine the ratio of the circumference of main drive wheel for the tracks to the circumference of the front. You are trying to make sure the distance covered by each is the same. For example if the track sprocket was half the circumference of the front wheel you need it to turn twice as fast to cover the same distance. I had to work some of this out in my build: jebster's half track lcc mog

Wish I had the ability when I did mine to 3d print out a transfer case. I like this much more than what I did.

This is a sweet build by the way. I love different.

[BigSki]

Originally Posted by jebster

Your on the right track. You need to determine the ratio of the circumference of main drive wheel for the tracks to the circumference of the front. You are trying to make sure the distance covered by each is the same. For example if the track sprocket was half the circumference of the front wheel you need it to turn twice as fast to cover the same distance. I had to work some of this out in my build: jebster's half track lcc mog

Wish I had the ability when I did mine to 3d print out a transfer case. I like this much more than what I did.

This is a weet build by the way. I love different.

Ahhh, I was close, as you say, but not close enough. It makes more sense now- the track's circumference isn't part of the equation because the linear distance it moves would have to match the linear distance of 1 tire rotation, which is a function of how fast the drive wheel is turning.

Thanks for helping ITG, and me, in the process.