question of tyres

Hey john,
I am glad you are doing this. I have had ideas about partially wheeled sleds that have been rolling around in my head for a while and I am excited to see what you come up with. The idea seems great, but braking could be a limiting factor depending on how you rig it up. Are you going to have a pole to hold the load back? If you have 2500 lb load, and are only dragging 750 lbs, you only have maybe 375 lbs of drag. The whole thing could take off on you on a downhill of 15% or more. Something to think about… if you put the wheels behind the bunk and elevate them compared to the runner height, the wheels will only engage when there is a pull in the front of the sled, which elevates the front sled runner. In a braking situation, where there is no pull in the front, the runners would be engaged ( not the wheels). If designed carefully, you could have the draft advantages of wheels, and the brake and loading advantages of a sled, best of all, the braking would be automatic and exactly proportional to the load. If you put a pole on this, you could have even better braking than with a sled b/c braking would essentially jackknife the front of the sled into the ground. Something like this is what I kept toying with in my mind. Feel free to take it if you want. I am curious to see what you come up with. 😮

Very nice. Thanks for sharing Simon. Both of these designs have the bunk placed ahead of the wheels (just a few inches in the first picture, a few more inches in the second) and they would have the automatic braking effect I was referring to. All these neat little ideas that seem to roll around in my head seem to be already invented by Scandanavians. Funny… I really like these designs, particularly the red one.

Are you making this for one horse or two? How much articulation will there be between the from of the the runners and the shafts or pole? This might seem to not matter much, but if the runners are able to lift up a little in the front, it would put almost all the weight on the wheels. If this happens, the skids would primarily be for braking and would change how they might be designed.

Jac
we get some plastic barrels over here from blown in insulation, cooking oil and other stuff that is pretty tuff, a couple layers might last a season, about $20 for used barrels, some free.

@jac 33487 wrote:

I have dabated with Simon over whether the shafts should be able to move up and down freely but as im a beginer at logging on a big scale Im not sure..was just looking at it from an engineering point of view an thought it would give another bit of articulation and act like an automatic brake when the horse sits back in the breeching ??

From where I’m sitting, I think your are both right. Verticle articulation would not only act as an automatic brake when the horse sits into the breeching, but would also maximally load the wheels when it pulls and take most of the load off the skids. A good thing in my mind. If you had unlimited articulation, however, you would just pull the wheels out from beneath the thing and it would flip backwards. You could have the best of both worlds if you found a way to limit the articulation such that the skids could be lifted up off the ground, but the wheels couldn’t be pulled out from underneath. Lots of ways to do this on paper, and I think you know what I mean. That one of the things I really like about the red design in the photo. It looks to have limited articulation from those chains, although I can’t exactly figure out how that central connector works… Perhaps this is a tilt limiter or sorts?

I know this is kind of an old thread but I just found this site a few weeks ago. Just an observation,tall tires will roll a lot easier,also narrow tires will roll easier and go through the mud easier also. JMHO

carl ny