AstroDesigns
Telescope Transport Devices

Scoporter Tripod Sled

by Rob Preston  <rbrtprstna_tearthlink.net>

I made this 8" LX200 transporter after I moved to a house that had enough space to store the scope/wedge/tripod fully assembled. However, the tripod legs needed to be retractable during transport to get past a doorway and some trash that's always in the way. Dave Dixon's design of a similar transporter is made with nicely machined aluminum parts and is commercially available. My design has an amateurish "feel" that provides an attractive counterpoint to the high tech gear that it carries. Also, it includes a tripod leg retraction mechanism that could be useful by itself, without the transporter. I've always disliked the floppiness of the Meade field tripod legs in their retracted state, and the obnoxious binding that can occur when unfolding the legs to set up a scope. This leg-retractor solves those problems with common materials and tools as friendly as the hacksaw.

DISCLAIMER

THIS TRANSPORTER IS NOT FOR EVERYONE. It is somewhat dangerous to support the full weight of an LX200/wedge/tripod several feet above the rather small footprint provided by two dolly wheels only 20 inches apart. The center of gravity is high, and it could bounce past the footprint if one of the balloon tires hit a rock or a hole under the wrong phase of the moon. Especially if the tripod legs were retracted, this would be a disaster for the scope. Worse, one could easily rip a vertebral disc or get oneself crushed trying to SAVE an expensive scope from taking the fall. If, like me, you know that those things only happen to the other guy, then go ahead and build it. However, I recommend that the tripod legs be retracted only when negotiating narrow doors or passageways. Extend and lock them whenever possible, so the tripod has a chance to stop the fall if the unexpected happens. Don't speed with the dolly (stars move too slowly to make that worthwhile) and finally, friends don't let friends transport telescopes drunk.

The attached pictures of the transporter are mostly self-explanatory. Construction is by the time- honored cut-and-try method using scraps of lumber, mostly pine, left over from home projects. No dimensions are critical (if they were, I wouldn't be here to write this). A poor man's Scopesaver? made from 3/8-inch plywood is inserted between the wedge and the tripod head. The 3/4-inch pine forks that lift the whole rig by lifting the plywood Scopesaver are attached to the dolly's round steel uprights by squeezing the upright using a second piece of wood and four long 1/4" - 20 bolts. The right amount of squeeze, applied by uniformly tightening the four bolts, causes the pine to become slightly compressed along the line where it touches the round steel upright (see scoporter5.jpg). No need to overtighten, there (and certainly make the wood grain go perpendicular to the steel upright, not parallel - you don't want the steel doing karate splits of the wood while transporting a scope. The 1/4"-20 bolts that attach the wooden forks are located right up against the steel tube to add some insurance that the wooden forks won't shift or fail. These forks measure 5 inches vertically at the steel dolly upright, in this version. Some day when I have some 1x10 lying around I'll make new arms that are 10 inches high so the torque at the joint won't be so high (10" would still clear the tripod legs when they fold out).

The rear leg is a piece of 3/4-inch pine with 1x2's bolted onto its sides to provide holes for the hinge. This is described in the legend to scoporter4.jpg. A broom spring-clamp at the bottom of the leg holds the leg against the dolly's axle during transport, and two lengths of chain limit the extent the leg opens out from the dolly so the center of gravity of the scope is near the middle of the triangular footprint formed by the leg and the two wheels.

To make the leg-extender, a long piece of 1/2"-13 stainless all-thread is attached tightly to the tripod head with nuts above and below the head. (Alt-Az'ers will need to modify this somehow). See Scoporter2. The all-thread extends all the way down past the point where the aluminum leg- extension limiter bars normally sit while the tripod is in use. The central aluminum plate to which the leg extension-limiter bars attach is the core of the mechanism: it has been bored out to accommodate a short length of brass tubing that telescopes up or down over a second length of tubing which in turn covers most of the length of the 1/2"-13 stainless all-thread. The short brass tubing is hard-soldered at its lower end to a 1/2"-inch steel washer, and that washer is bolted to the bottom of the aluminum plate that holds the leg extension-limiter arms. The longer brass tube on which the short one rides is positioned on the 1/2"-13 all-thread with nuts at both ends. As the short brass tube trombone-slides up the inner brass tube, it raises the leg-extension-limiter arms and pulls the legs in smoothly. An aluminum brace attached to the dolly near the bottom provides support for the weight of the 1/2"-13 all-thread (when the dolly is in its laid-back position), and the all-thread in turn supports the weight of the tripod legs transferred through the slider plate. The upper triangular plate that forces the legs to extend operates in the usual way. The large knob that lifts that plate is no longer locked to the 1/2"-13 rod, but screws freely up and down the rod. Note that the rod itself cannot turn since it is locked to the tripod head. The knob spins very easily on the all-thread, and the legs extend at nearly the proper angle from each other, so locking and unlocking the legs during set-up is a much smoother task than it used to be. I should patent the mechanism but what the hell.

 

Overview of Scoporter

Scoporter1 - shown in position for extending or collapsing tripod legs, with legs collapsed.

Mounting bolt assembly

Scoporter2 - view of leg extension/collapse mechanism based on 1/2"-13 all-thread.

Top view

Scoporter3 - view with no scope present, showing the wooden arms that lift the scope.

Close up of arms

Scoporter4 - detail of the hinge for the rear bracing leg, made from 0.5-inch diameter thick-wall aluminum tubing covering a section of 5/16"-18 all-thread. The tubing and all-thread extend all the way through the various wooden parts. In a former version, the 2 sections of pine 1x2's shown here bolted to the sides of a larger piece of 3/4-inch pine board were used as two separate legs spaced further apart (hinged in the space shown directly behind the dolly uprights) and joined rigidly at their lower end. With the two rubber tires, that version had a four-point connection to the ground that was liable to rocking motion when the ground wasn't perfectly planar (which it never is). And with $3000 worth of scope and gear balanced on the dolly, ANY rocking was just too scary to feel. Thus, the current version with a three-point geometry (there's a short dowel extending from the center of the bottom of the 3/4-inch board.

Extreme close-up

Scoporter5 - detail of the dolly leg clamping method, showing the wood slightly compressed around the steel dolly tube. 1/4"-20 hardware.

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