simonr Posted September 15, 2015 Share Posted September 15, 2015 I have acquired the components from 1 1/2 of these: (It's a long story). I have one ish complete vehicle less the plastic bits, front skids & seat plus spare sets of tracks, running gear, CVT & Gearbox (High, low & Reverse). I thought it was too good an opportunity to pass up for the very limited amount of money - but have not decided what to build out of them! It has a 1.6L Ford Turbo Petrol engine coupled to a Variomatic CVT, into the gearbox - then a geared transfer box to both tracks, sadly, not through a differential. The first job is to decide what sort of steering. The simplest would be to add a Diff inbetween the tracks and a couple of disk brakes to slow one or the other track. However, this wastes a lot of energy, is apparently hard to keep in a straight line and will not centre-steer (tracks moving in opposite directions. Next possibility is a double differential - imagine two diffs side by side with the two middle shafts connected together and that driven by the engine. If you hold both crownwheels stationary, both tracks will move at the same speed. If you drive the crownwheels in opposite directions, the rotation speed is added to one track and subtracted from the other. Normally the two are connected to a third differential such that turning the input one way or the other steers the vehicle. Turning the input with the engine not driving the tracks steers on the spot. You would normally turn the third diff with a hydraulic motor and proportional reversing valve (or an orbitrol valve). It might be simpler to use a pair of motors plumbed to turn in opposite directions & connected in series via the valve - I don't know if this is used anywhere. If any of you have experience of track steering systems - I'd be very interested! In particular if a Brake steer with a differential is worth considering. Next is what sort of vehicle to build. The original chassis will have to go as the tracks are too close together to steer and to fit a diff in-between. Thus, the world is my oyster as they say! Each track is about 2m long & 30cm tall with suspension for the bogey wheels and an automatic tensioning system. The tracks are rubber with PU covered steel bogeys which are fairly good at keeping the tracks on. In High range (on Snow) it apparently has a top speed of about 50mph - so it could be quite fun! Quite a major build though! Any ideas or inspiration welcome! Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted September 15, 2015 Share Posted September 15, 2015 No ideas yet, just interested to see what you end up building Quote Link to comment Share on other sites More sharing options...
miketomcat Posted September 16, 2015 Share Posted September 16, 2015 Could you build it half track style or perhaps have 4 sets of tracks front 2 steering or bend in the middle. Mike Quote Link to comment Share on other sites More sharing options...
elbekko Posted September 16, 2015 Share Posted September 16, 2015 Build a Hagglund! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 16, 2015 Share Posted September 16, 2015 Whatever you build, it needs lasers. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted September 16, 2015 Share Posted September 16, 2015 Mini hagglund for sure Quote Link to comment Share on other sites More sharing options...
L19MUD Posted September 16, 2015 Share Posted September 16, 2015 if you built it with 4 tracks and a pivot in the middle you could possibly use a small dumper truck as a chassis? Might be too heavy? Then sit the other way round to a dumper and ditch the skip. You can then have any style body you want on the side the skip normally sits Quote Link to comment Share on other sites More sharing options...
L19MUD Posted September 16, 2015 Share Posted September 16, 2015 Just googled what a hagglund is.....much better idea! Didn't realise that was what they were called. I looked at a couple in the Falklands. They are not actually that big when they are full size. Looked very cool if a little basic Quote Link to comment Share on other sites More sharing options...
Arjan Posted September 16, 2015 Share Posted September 16, 2015 Interesting Project We have a ArgoCat Conquest here for the MRs. to use and that is an 8x8 skidsteer. The setup works very well - and great fun. Basically the variomatic drives the diff - either side has a disk brake you operate. Please keep us informed - very interesting to see where you eventually will end up with... Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2015 Author Share Posted September 16, 2015 The hagglund's are interesting and probably very capable - but look a bit long & not very elegant! Best option I've seen so far is something like this: On a slightly smaller scale. I wondered about a half-track and actually work with a guy who built one in the past. Good to know that Brake steer works on an ArgoCat - probably means it would work OK on this. This is what I've done said deal on: Quote Link to comment Share on other sites More sharing options...
miketomcat Posted September 16, 2015 Share Posted September 16, 2015 https://youtu.be/XKgi2g-uUBI Mike Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted September 16, 2015 Share Posted September 16, 2015 Looks far too energetic to me! A version of that that you can sit in would be great though, definitely need roll over protection though! Quote Link to comment Share on other sites More sharing options...
landroversforever Posted September 16, 2015 Share Posted September 16, 2015 mini hagglund like this would be perfect for sodbury sortouts: http://www.ljacksonandco.com/index.php/hagglund-bv206/models-available/article/32824-hagglunds-bv206-soft-tops Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2015 Author Share Posted September 16, 2015 https://youtu.be/XKgi2g-uUBI Mike That looks cool! It would need the full 3 differential steering system to get the agility. I agree something you sit on with roll protection - maybe a tracked Rzr? Si Quote Link to comment Share on other sites More sharing options...
simonr Posted September 16, 2015 Author Share Posted September 16, 2015 The answer to the steering is kind of obvious. Put a single differential in the middle with two disk brakes - then use an ABS / TC module to control the brakes. Use a microcontroller to control the on/off ratio of the brakes on each side to maintain a constant speed ratio, proportional to the steer angle. That pretty much guarantees it will drive in a straight line and corner smoothly. The issue (apparently) with brake steer is a corner is faceted - like the outside of a 50p coin, made of a series of straight lines rather than a continuous curve. This makes handling at speed a potential problem. Since it's only going to use 2 of the 4 outputs on the module, the other two could be used to implement force feedback through the steering - which will force the steering back to the centre and give resistance proportional to speed. Si Quote Link to comment Share on other sites More sharing options...
miketomcat Posted September 16, 2015 Share Posted September 16, 2015 Here is the original: https://youtu.be/p_iup2jXQqI And mk2: https://youtu.be/P5FjZUwe000 And the one I posted first is an off shoot. Mike Quote Link to comment Share on other sites More sharing options...
muddy Posted September 16, 2015 Share Posted September 16, 2015 Stick two wheels in place of the skis and try it off road!, I remeber watching a vid of a guy on the road with one and have always fancied trying it off road. Will. Quote Link to comment Share on other sites More sharing options...
pat_pending Posted September 16, 2015 Share Posted September 16, 2015 The side loadings on a track steered undercarriage can be huge. I think you may have problems with track shedding, as those units weren't designed to steer, or run on higher traction surfaces. Quote Link to comment Share on other sites More sharing options...
discomikey Posted September 16, 2015 Share Posted September 16, 2015 watching with interest! Quote Link to comment Share on other sites More sharing options...
simonr Posted September 17, 2015 Author Share Posted September 17, 2015 The side loadings on a track steered undercarriage can be huge. I think you may have problems with track shedding, as those units weren't designed to steer, or run on higher traction surfaces. I agree. I plan to widen the track to 1.6m which is 60% of the track length. Apparently this is a golden ratio for tracked vehicles in terms of steerability etc. Things like the RipSaw above employ keepers on the drive wheels which I imagine help with shedding. Si Quote Link to comment Share on other sites More sharing options...
dangerous doug Posted September 17, 2015 Share Posted September 17, 2015 Si, I recently saw a program called combat dealers and they raced a pare of ww2 half tracks across a field, German vs the American one. one had something similar to the twin diff you speak of and the other used skid steer, I forget exactly which was which but the American one won due to its lack of skid steer. Might be worth finding it on catch up as you might get a pretty good comparrison Quote Link to comment Share on other sites More sharing options...
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