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| Dumb New Guy With Big Ideas; M3A1 TLT half-track | |
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| Topic Started: Jun 10 2006, 06:38 PM (516 Views) | |
| dremelit | Jun 10 2006, 06:38 PM Post #1 |
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Swayed by the Trax
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Greetings boys. For you who don't know me, I'm one of the weenies from Scale4x4RC, and thought I'd bring this over here for a bit of advice, since this is the place for tracked vehicles. Anyone had a go at a half-track yet? I work in a hobby shop, and had a customer bring in a tracked robot creation made with Krex (?) tracks bought at Radio Shack- fairly good sized tracks, the main sprockets are about 1-1/2 inches around, and the tracks are nearly as wide. bogey wheels about 3/4 inch diameter, non-suspended (hard) in this application, but they might be springable with some creativity applied. Maybe transverse leafs? As it happens, one of the chaps from Scale4x4RC (exesivefire) was there at the same time, putting together his latest TLT project. So my mind went <click> and connected the two, coming up in a split second with an M3A1 half-track using TLT axles and these tracks. How freakin' cool would that be? It would run on 4-4.5 inch front tires, so it would be fairly huge. I haven't scaled anything yet, but i'm guessing somewhere in the neighborhood of 24-28 inches, and correspondingly heavy. If I had to guess, let's call it 20 pounds. This will take some serious research on my part before any building starts, since i know Jack about tracked vehicles, let alone half-tracks, so i have no idea how to make it steer, but the cool factor would be off the chart. I'm guessing a pair of wheel brakes applied to the drive sprockets, activated by a servo that's Y-harnessed to the front wheels' steering servo. Would this extra bit be necessary, or would the rear diff be sufficient for steering? The front wheels would be driven, if that makes any difference. The cost factor is no small consideration, and I have quite a few projects on my plate that need completing before I start another one of this magnitude. I will be shocked beyond belief if I can bring this to completion for less than $1,000. That's a major problem for me, but the engineering challenge makes me want to do it nonetheless. Still, it's something to think about  Looking forward to any insight you guys might have on this. So fire away, let me have it!  Stu |
Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| outcastrc | Jun 10 2006, 07:25 PM Post #2 |
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First thing, glad to see you coming over to the dark side!
 I don't know those radio shack track systems at all but I have an idea that might be a lot cheaper to pull off. You can pick up a Heng Long cheap and use that for hacking into a 1/2 track. I think that would be a lot easier and more realistic at the end of the day. It might be a perfect (or near enough) to 1.9 wheels. Its actually something I am thinking about myself maybe one of these days. I don't see where it would be too hard to pull off, unless of cousre you want to power the front axle and then you'd have quite a few issues to figure out... I can take some pics if you'd like so you can get an idea of it. |
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| outcastrc | Jun 10 2006, 08:23 PM Post #3 |
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Heres some pics just to get a feel for things... I wouldn't try the tiger myself unless they were smaller tires but the pershing (or walker) would make great candidates for a hack fest...   
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| dremelit | Jun 11 2006, 02:55 AM Post #4 |
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Swayed by the Trax
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I really want to power the front axle, and drive the tracks with an axle rather than with two motors. It's more about building a half-track than having a good-looking model, but the Krex (still not sure of the name) tracks actually look pretty right, Only the rear (non-driven) sprocket is not to scale, and I can hack something up there. This build would be so amazingly complicated, I almost have to do it at this point, just to see if I can. Once you've made a functional rollback tow truck, there ain't a hell of a lot of new ground to cover 
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| spoon37 | Jun 11 2006, 06:25 AM Post #5 |
Trax Master Poster
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Welcome Stu!! I have often wondered how a half track works in regard to steering etc, more so since I got my blizzard. having been used to driving wheeled vehicles off road it was a bit of a suprise to have to learn how to drive a tank. from my point of view the biggest difference is that the direction changes when the tank goes over rough ground(like where a truck would articulate and go roughly straight, the tank suddenly changes direction) so to drive straight over rough terrain is a challenge. hiow this works with a half track I have no idea. what I do know is that simply turning the front wheels will do nothing unless the tracks are able to turn at different rates, but at the same time full tank steering would actually drag the front end around especially if its setup to allow for neutral turns. I guess that if it were setup like a 4x4 with open diffs but tracks instead of rear wheels it could work, I just dont know if you would need extra turning impetus for the tracks? e.g. a brake per track like the blizzard uses... the way I see it something is going to scrub when turning a half track as even the outer ends of tracks on a tank scrub when turning(this is why tank tracks can never be made really long) 
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| outcastrc | Jun 11 2006, 07:25 AM Post #6 |
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Yah modifying a Blizzard would be the next best thing. You already have the open diff and braking bias set up for you. The other huge problem beside getting it to steer is the different ratios between the tracks and the tires. It makes me wonder if a real half track was really an decent design. Or was if fighting itself just to move and turn. |
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| spoon37 | Jun 11 2006, 11:07 AM Post #7 |
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dunno... but I would guess most dont have driven front wheels?
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| outcastrc | Jun 11 2006, 12:13 PM Post #8 |
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I can see how the smaller track ones would work. There is less track on the ground so the front tires can bully to steer. But when you start seeing the German ones you have to wonder how it can steer at all. The tires should lose to the size of the tracks. It sounds according to the net that the front tires steered when it was mild turns and major turns had track braking help. One benefit of the design is when used in the enviroment they were meant for the dirt would allow the design to plow its way thru a turn. I imagine on pavement the design would be much worse. With the tracks dragging the tires thru major turns. And the tires straining to get the tracks thru mild turns... All conjecture tho... The worst one for this is prolly the Kettenkrad (the motorcycle tank) I can't imagine how a motorcycle front tire could do much against the rear tracks... |
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| dremelit | Jun 11 2006, 02:42 PM Post #9 |
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Swayed by the Trax
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time for actual research, then
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| dremelit | Jun 11 2006, 02:53 PM Post #10 |
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tell me that ain't a differential under there. http://images.google.com/imgres?imgurl=htt...cial_s%26sa%3DG as for getting the drive ratios right,  add that to the list of stuff i hadn't even thought about.
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| dremelit | Jun 11 2006, 06:47 PM Post #11 |
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Swayed by the Trax
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Well, the front axle is definitely driven. Every half-track site i've been to tonight confirms it. I'll have to speed up the rear axle (track drive) to compensate for the smaller drive wheel. That's what they did on the 1:1 M3's. I'll have to leave the center diff open, too. That'll cut the turning radius down. See, if I start working all the difficult bits out now, then it'll go together that much easier if and when I actually start to build it. |
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| spoon37 | Jun 13 2006, 01:15 AM Post #12 |
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Trax Master Poster
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oh yesh....
:lol: I must admit my thinkingh is more along the lines of a German 18t half track "Famo" (Sd.Kfz.9) http://www.zobten.de/Famo/SdKfz9_2.jpg getting one o them to turn must have been fun....
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| dremelit | Jun 13 2006, 03:56 AM Post #13 |
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Swayed by the Trax
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I'd imagine they had hydraulic steering, some sort of mixing arrangement between the wheel and the tracks. Otherwise the driver would be real busy :rofl: |
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| spoon37 | Jun 13 2006, 09:22 AM Post #14 |
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Trax Master Poster
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well it stands a good chance, many of the German vehicles were over-engineered, chances are it used a fantastically complex system that allowed it to turn on a dime with only the slightest effort from the driver...
:lol:
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| outcastrc | Jun 13 2006, 09:32 AM Post #15 |
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That would have saved at least one crews life because they broke down before getting to the front and the war was over before they got the parts.  I remember a show on the Tiger and that is exactly what happened to the crew of one. Those must have been happy guys looking back on things. They may have been the best tanks of the war but they were marked targets. Not many survived to tell another tale. Back to the topic at hand. If it had a center diff you could leave the ratios wrong and the center diff would compensate for it. But the bad side of that is technically you could have one front tire spinning and going nowhere... But if the tracks had the motor attached to that side so it can't unload. then the front could unload but the rear would be forced to get power. 
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| spoon37 | Jun 13 2006, 09:39 AM Post #16 |
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AFAIK just 1 Tiger I survived the war......
but yeah, the Germans may have had superior engineering but it didnt exactly help the war effort much.... a centre diff would normally mean reduced traction IMO, but with rear tracks is that gonna be a problem? I mean the blizzard climbs so well it makes all my trucks look ill equiped for rough terrain.... :rofl: |
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| dremelit | Jun 14 2006, 03:36 AM Post #17 |
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I was planning to leave the center diff open, just to help with the turning radius. And the whole goofy-gear thing. I'm sure I won't be able to get it 100% right :rolleyes: so a little fudge factor will help there. aw, bugger it. No more new projects, I might as well get this one underway. I'm not going to stop thinking about it until I build the bastard. 
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| outcastrc | Jun 14 2006, 06:27 AM Post #18 |
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LOL You'll do this in Dremelit time anyways. So it should be finnished long before any of us can get anything done!
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| dremelit | Jun 16 2006, 03:20 AM Post #19 |
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Swayed by the Trax
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The real challenge will be leaving those TLT axles alone until next year. Does anyone really think i can do that? |
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| outcastrc | Jun 16 2006, 03:51 AM Post #20 |
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Never! :rofl: |
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| spoon37 | Jun 16 2006, 04:42 AM Post #21 |
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:rofl: 
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| dremelit | Jun 23 2006, 02:35 AM Post #22 |
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Swayed by the Trax
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I may have solved the front-rear drive ratio discrepancy. And as usual, I did it by not thinking about it. Then the most elegant solution hit me as I was laying me down to sleep last night. If I use a Stampede gearbox, I'll make the front tires 2.72 times the diameter of the rear drive sprocket. Drive the front axle conventionally, off the tranny's output shaft, and drive the rear axle off the input shaft. Not only is it simple and elegant, but it raises the rear driveshaft just a scosche. Damn, I'm good
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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| spoon37 | Jun 23 2006, 04:22 AM Post #23 |
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genius.... thats a pretty exact number tho...
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| outcastrc | Jun 23 2006, 06:05 AM Post #24 |
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That would work! Does that make for a small front tire or would it be scale? Sounds like a 1.9 might fit the bill... I would think as long as its close there would be minimal scrubbing. And if run on dirt that wouldn't matter anyways. 
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| dremelit | Jun 23 2006, 12:59 PM Post #25 |
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errr.. actually, it makes the front tires (and the overall build) fairly huge
Since the rear sprockets are ~2 inches, I'd need 2.72x2in, or 5.44 inch front tires. Once I get the tracks, I'd have to measure for sure, but that's the ballpark we're playing in. |
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Dremelit is one of the few men I'm actually afraid of! His brain works at 4 times the speed of you or me, he actually tries to make his many ideas come to fruition, and has NO idea what an obstacle is: He has balls that clank, and one hand was lost in an accident, so he had a Dremel grafted on-It even has an attachment that lets him hold ANOTHER DREMEL! Whenever this guy is stimulated, take my advice & run for the hills!
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