tracked vehicle differential questions

[SensibleNick]

So long as you know we're not all talking about the same thing

The original tensioning system on the BV202 is fairly hefty, and the BV202 is a far heavier vehicle than I have in mind for my toy... so it'd be overkill.

Tracks are relatively easy to come by (here in Sweden), but the machines themselves are like hen's teeth or redicilously expensive when they do come along. Besides... butchering a working machine for just one part would make me feel bad.

Yes, it'll be an engineering challenge, but compared to things I design daily it's a fresh breezy walk in the park with a zz-top soundtrack. I won't be breaking any new territory, but I'll be able to do things *my* way - Most likely scenario is moving the mount for the drive wheel. Given that I'll probably end up messing about with different drive solutions, having a modular unit at the drive end of things is a nice way to ensure I don't have to hack the entire pontoon about each time I want to try another drive system

PS... I hope Dave agree with me on this one, but as this is not a build thread, and seems to be more along the lines of what you say in your last post - dissecting the issues one by one and mulling over the ideas involved in making something like this happen. As such (from my part at least) there's no need to apologize for poking ideas, questions and suggestions in - it's all welcome and would help us get to a better solution in the end.

 

[davedj1]

Yes, it's good to have many minds mulling things over. I'm no engineer but enjoy building things. I enjoy reading what other people are thinking, doing and wishing they could do.
At least when the time comes to actually start the builds we will be much more informed and hopefully have some better ideas of what we want/need to do.

thanks guys, keep the good words coming,
dave

 

[oughtsix]

Cool, I enjoy mulling things over.

Dave am I correct in my understanding that you are thinking of using a Samari motor for powering the vehicle? Are you considering using the stock trans axle? This seems like it might be a problem as I believe there is a transfer case with a rear facing output shaft to drive the rear wheels??? Would you just be able to ignore this output shaft? Do you have a 2wd Samari you are thinking of using?

Nick, what are your thoughts on the power unit for your vehicle?

 

[SensibleNick]

Nick, what are your thoughts on the power unit for your vehicle?

I know it's a more expensive option, but I want to make an "easy to use" machine that my young lad can use when he grows up... so hydraulic drive is on the table here.

I had been considering the $1800 stack of pumps that Surplus center have.
(go look at their HST pumps and you'll find a pair of variables mated to two gear pumps).

I then realised that that setup was totally "overkill", and took a single step up their list to the 1.10cu pumps. A pair of those driving a pair of the smaller wheel-motors they have should give me 30mph (plenty) and some massive torque. (Which equates to the top of each track being pulled along with a force of 1.5 tons)

For the other hydraulic pumps Something small and v-belt driven will fix the auxiliary bits and bobs (8gpm?) and a larger pump coupled to a PTO-splined motor.

I'm wondering whether I should go gear-pump and spool-valve for the PTO system, or HST pump?

The Engine... Originally I wanted 100bhp (seemed like a good figure) but now I think 60bhp is more realistic. I won't be using full drive capability AND full PTO power at the same time - it'll be one or the other.

So a 1.5 diesel will do the job. Maybe something from a small french FWD car? Peugeot or Renault... or maybe the ford 1.8D?

I'm not decided on that one really.. though it MUST have a mechanical injection pump for simplicity. A Turbo might be a bad idea given that I want low-down grunt.

I don't need to retain the clutch, so the hub of the flywheel can have a CV Joint mounted on it, and the Pumps can be driven from a simple pillow-blocked driveshaft using rear sprockets from motorbikes and some decent chain (usually good for 100bhp applications, and more efficient than belt-drive).

I considered dry-sumping the engine too to get the Center of Gravity lower... and then I realised I was getting carried away... though with this machine probably getting some time with it's nose or bum high in the air, maybe it's a good idea.

Fun anyway. I find meself stood in the shower at the end of the day, whistfully staring out of the window trying to get a good idea of the control layout on it and trying to work out how much use it'll be.... :ashamed:

 

[davedj1]

I am contemplating using a Suzuki Sidekick, 96 ish. I am planning on doing away with the front axle completely and running it from the rear. I'm hoping to leave the steering wheel and somehow rigging the brake master cylinders so it will brake steer when you turn the wheel.
I will lose the rear suspension, moving an axle down and mounting it solid to drive the tracks.
I wish I knew how to use an auto cad program......LOL
I still do things the old fashioned way, a sketch pad and some trial and error.

Nick, we (our snowmobile club) has a Cushman Trackster that has the dual pump/motor setup, it runs off a joystick and is very responsive. You have to be careful! If it was up to me I would have made it into two separate control levers. After the engine swap it took forever to get the linkage lined up perfectly so everything would work as it should.

 

[SensibleNick]

hmm... Joystick V. dual Lever....

I'd probably play with both layouts, but in the name of simplicity the joystick will have to wait. If I manage to make it "fly by wire" as I hope, then joystick becomes easier as I can program in a less sensitive control system if needed, or essentially a digital "difflock" to ensure it only goes straight when I want it to. The limits are endless to be honest.

But to start with... two levers - there's something very pleasing and basic about two levers.

 

[Iplayfarmer]

...I had been considering the $1800 stack of pumps that Surplus center have.
(go look at their HST pumps and you'll find a pair of variables mated to two gear pumps).

I then realised that that setup was totally "overkill", and took a single step up their list to the 1.10cu pumps. A pair of those driving a pair of the smaller wheel-motors they have should give me 30mph (plenty) and some massive torque. (Which equates to the top of each track being pulled along with a force of 1.5 tons)...

I've mentioned this before, but I don't recall if I've mentioned it on this thread or not.

Look into golf course reel mowers. You have all the parts you need: Wheel Motors, hydraulic pumps, power steering valves, hoses, etc. You can likely pick up a broke down reel mower for pretty cheap and leave more money for other parts of the build. I have three sitting in the back of my pasture that I am still scrapping parts from. I'm assuming that they have golf courses in Sweden.

 

[SensibleNick]

I've mentioned this before, but I don't recall if I've mentioned it on this thread or not.

Look into golf course reel mowers. You have all the parts you need: Wheel Motors, hydraulic pumps, power steering valves, hoses, etc. You can likely pick up a broke down reel mower for pretty cheap and leave more money for other parts of the build. I have three sitting in the back of my pasture that I am still scrapping parts from. I'm assuming that they have golf courses in Sweden.

We do have golf-courses, but most are mown with tractors. The other thing to consider is that the entire Swedish population would fail to fill London in the UK. There are 2 million too few people to do the job. Golf course concentration is fairly low.

Part of the fun for me is building from scratch and being able to spec components that I want to use. Although shipping a crate from the US is going to hurt financially, the vast array of tasty goodies that SurplusCenter has is stunning - and makes it all worth while.

Given that I've managed to "save money" by going the cheaper pump route, I can also add some extra goodies to the package: 3 cylinders for the front 3-ppoint (allowing for top and tilt) 1 cyl for the rear 3-point, and a pair of cylinders for the snow-pusher's wings. :licking:.... might just have to buy myself that plasma-cutter too

 

[Iplayfarmer]

Part of the fun for me is building from scratch and being able to spec components that I want to use.

Understood. I can totally respect that.

Part of the fun for me on a creative build is re-purposing old parts rather than buying new. For some reason I feel like I get extra creativity credit for using old parts.

 

[davedj1]

I wish we could "find" used equipment like a golf course mower, they must go to employees as I never see anything up for sale. Maybe I should stop by and ask, there are about 6 of them in a 30 min radius.