DIY Prototype Log skidder (V.1.0)

patrick_g · Mar 21, 2007

I have been skidding some logs and need something better than just chaining to the box blade but not nearly so advanced as the fancy arch things with wheels and such.

Here is the dialog for the 4 pix:

#1 shows MDF templates for cutting round pieces of steel with the plasma cutter, two each round pieces of each diameter, and about 18 inches of approx 5 1/2 OD pipe with 5/16 wall thickness.

The smaller circles fit the pipe ID and the larger circles are about 7 inches.

#2 shows a class 1 pin to fit the lower arms of the 3PH inserted in holes drilled in the round pieces. Both are welded all the way around the pin on both sides.

#3 shows everything put together and tacked

#4 shows the finished prototype installed on the tractor

In use you attach your chain or cable to the drawbar seen in the upper right of photo #4 (boxy looking thing) and lead it over the top of the LogTow thingy and then to the end of the log. The LogTow thingy is free to rotate so when you raise and loser the lower arms of the 3PH the chain doesn't slide acoss anything, instead the Log Tow thing rotates to give the chain or cable a spooth way to go.

The plan is to lower the 3PH all the way with the tractor backed up to the log so as to minimize chain length. You wrap and secure the chain to the log then run the other endd over the LogTow thingy then through the drawbar and back over the LpgTow's drum and hook wherever yo need to to remove the excess slack. You then raise the 3PH lower arms so as to pull the end of the log into the air so you can tow it without it plowing or hitting stumps.

The extra diameter of the round pieces at both ends helps keep the chain or cable from getting off the drum. After I try it out I will know it the round ends are large enough in diameter or need to be larger. I will be testing it pretty soon if we don't get enough rain to keep me away from the loging locale due to mud. I don't want to rut up any pasture getting to the logging locations.

P.S. The smaller circle of steel is a good fit for the ID of the pipe. If you try to push (bend) the pin out of alignment (parallel to axis of pipe) the end of the pin inside the pipe is supported 360 degrees by the smaller circle of steel. I had thought I would have to drill at least 3 holes in the pipe to weld the little circle to the pipe but I got such a good fit I don't think it is needed but could always be done later.

Pat

HomeBrew2 · Mar 21, 2007

Cool!

If I'm picturing it right, you get a bit of mechanical advantage with it tied to the draw bar (?) as compared to straight lift w/ 3PH

patrick_g · Mar 21, 2007

Homebrew2, No, I don't think there is any mechanical advantage. In a static situation (how most all analysis is conducted) the line tension is everywhere equal. (If it weren't something would be moving.)

This rig approximates having a pulley up overhead with a line going up and over and back down. If you put a weight on one end and use your hands to hoist on the other end the force you have to exert is equal to the weight of the object (ignoring friction, the other standard analysis assumption.) The pulley just changes direction of the line pull. The pulley attachment however has to support twice the weight of the object since the tension in the line is equal to the weight of the object and there are effectively two lines pulling down on it at that tension.

In the prototype, if the drum were directly over the drawbar and the log was directly below the drum the 3PH would be at a mechanical DISadvantage of 2 to 1 and would have to lift twice the logs weight. As there is considerably less than a 180 degree wrap of chain or cable on the drum the mechanical DISadvantage is less than 2 to 1 and approaches a low figure something like maybe 120% of the weight of the end of the log.

As I don't think I will ever have to skid logs too heavy for the 3PH I am not too worried about the extra load on the arms. I have skidded logs so big I can only lift one end at a time with my FEL pallet forks and this was just chaining to the back of the HD box blade (1300 lbs, I think) With the LogTow device in place of the HD box blade I should have plenty of lower arm capacity. If we don't get too much rain in next few days I'll have empirical evidence of how well the little gizmo performs.

What you would gain in the above 180 degree wrap sceanario is log height. For every inch of vertical travel in the drum (lower arms) you would pull the log up 2 inches.

In my prototype I'm guessing at about 120% disadvantage force wise so conversely I would get about 120% log lift for every inch of arm travel. A foot of arm travel would be about 14 1/2 inches of log lift. I'll know more when I use it.

Pat

jmc · Mar 22, 2007

Patrick,

I may be misunderstanding the description but it seems to me that if the log butt is contacting the roller BEFORE you lift, then when you lift it may try to stretch the chain. Looking from the side, the log butt tries to follow an arc centered on the drawbar with the chain length as a radius. but the roller is following the usual 3PH arc of a different radius and center. And if you leave the log just off the roller, will it contact when the tractor goes down over a hill?

Then if you don't have problems already, how will you turn with this log butt cinched up against the roller?

Ignor all this if your intention was to get the log on top of the roller.

John

patrick_g · Mar 22, 2007

jmc said:
Patrick,

I may be misunderstanding the description
Ignor all this if your intention was to get the log on top of the roller.

John

John, The chain has to be in tension to lift the log. The roller is free wheeling and allows the chain to roll on it without undue friction. Nothing interferes with raising and lowering the lower arms. You don't hook up such that when raised the roller is tight against the log. This limits the log diameter without hitting the roller with the log which I did several times today with no problems.

From this prototype (works just fine and has no problems along the lines you mention) I can see how to make some improvements, especially how to accommodate larger diameter logs.

Pat

HomeBrew2 · Mar 22, 2007

patrick_g said:
... (works just fine and has no problems along the lines you mention) ... /quote]

COOL!, you got to try it! Any pix and commentary of the maiden voyage?

patrick_g · Mar 22, 2007

Homebrew2, Didn't take camera, just chainsaws and tractor. It worked fine but could be improved by raising the drum to accommodate logs over 2 ft in diameter better. The drum just serves to give a smooth rotating surface to contact the chain as it is raised and lowered by the lower arms. A plain steel bar would work but the wear on the chain would be appreciable.

One idea I had was to run a cable from the FEL under the tractor over the drum and terminate in a loop. You attach the chain that is securing the log to that loop. YOU then raise the lower arms as needed to get the log up and raising the FEL will tighten the chain (poor mans winch.) Raising and lowering the FEL shortens and lengthens the drag line so the operator(s) don't need to fuss with the chain so much as you take logs of differing diameter.

If you use a block and tackle sort of arrangement then a small motion of the FEL will move the cable quite a ways (maybe a 4 to 1 or so.)

Pat