unwanted body movement.... cure for a little more than $100
I've just ordered BAL X-chocks today... I've heard they hold well and easy to use and greatly reduce unwanted movement for and aft. My 21RR tandem's tires are 7" apart and the cheapy expanding chock from Harbor Freight won't work.
I saw the idea of using cargo bars from Harbor Freight (SKU 96811) at $17.99 each... to make DIY stabilizer bars. I had $10 off coupon to boot.
You will need a hacksaw an electric drill motor with an assortment of drill bits up to 5/16" and simple tools like wrenches, ratchet, sockets, screwdrivers, etc. As for material, you will need 4 of the cargo bars; 4 pieces of structural grade steel channel iron - 1 1/2" ID... x 1 1/2" high "sides" by about 4" long; 4 ea = 2 1/2" x 5/16" lag screws; 4 ea - 5/16" x 4" grade 8 bolts; 4 ea - 5/16" x 2" grade 8 bolts; 8 ea - 5/16" stop nuts... had to buy stainless; 24 ea- 5/16" flat washers.
After fitting fuming and fussing. I came up with this method.
1) cut both factory feet off each end of each cargo bar.
2) Drill 5/16" holes about 3/8" from each end through both sides of pipes... mine had holes already in the right places, but too small. The holes through each end need to be parallel to each other and you might have to loosen the clamp on the bar while you turn the big, or hammer-tone end.
3) Drill 5/16" holes in the very bottom of the scissor jack. This is tricky, but if you have the same model jack as mine, the hole has to be as close to the bottom as possible, otherwise they will interfere with the action of the "gears". It is possible to get it too close to the bottom and the bolt hits the dimple on the bottom of the foot and won't run from side to side. So, the bar clears the "feet" of the jack in the folded up position, you have to angle the hole... actually 90 degrees to the direction you want the bar to run.... towards the middle of the floor. I got out my framing square, eyeballed it, made some marks... said a prayer and drilled. Be careful, it is easy to snap off a bit drilling an angle like this. I actually drilled from each side, saving the "drill through" for the 5/16"
Note: the front of the trailer is easier since you can attach the bars on the front or rear of the jack, In the front, I mounted the bars so one was on the front side of the jack, the other on the backside. On the rear of the trailer, you don't have this option, so with the bar to be mounted on the front side of the jack... angle one the minimum (about 20-ish degrees) and the other at a greater angle (30-ish degrees) so they will clear each other as they move up and down with the jack.
6) drill a 5/16" hole through the sides of the channel in the center... I drilled it as close to the edge as I needed to, but not too close... also drill a 5/16" hole in the center bottom. When I drill, I start with 1/8"... go to 1/4"... the 5/16"... your bits stay sharper longer and the final hole will be truer.
7) figure out where the floor joists are and make sure the place you choose allows the bars to fully extend and fully collapse... the 21RR has 2x3 floor joists with a space of 14" between them centered on the trailer, so planned to attach the channel to the joist nearest the center on the OTHER side of center. You can push up and feel the joists.
8) Loosely bolt (4") the shiny end (with the holes) of the cargo bar, to the jack foot plate bolt . I put 3 washer on each side of the bar.
9) Put the bar in the "free" or down position and push or pull the other so the hole in the back of the channel iron lines up with the joist you choose.
10) I held the other end of the cargo bar... hammer-tone painted in place while holding the channel like it was bolted on so the holes line up and the hole in the bottom is on center of the joist... let go of the bar (ouch!)... grabbed the drill and drilled the 3/16" into the floor joists about 2 1/4", but not to exceed 2 1/2" through this hole.
11) I actually used a drill driver to drive the 5/16" lags (head size was 1/2"), but ratchet and socket works well and could prevent you stripping out the wood if you accidentally over-tighten. Tighten the lag as much as possible.
12) bolt the bar to the channel iron leaving it free to travel.
13) tighten the bolt on the jack, leaving it free to travel
14) test by raising and lowering the jack that nothing binds excessively.
Assuming all goes well... test it. With the trailer level and positive pressure on all the scissor jacks, ratchet the cargo bars handle to tighten the bars... don't over-do it... you might get one click or maybe two.
Caution: before lowering the trailer always put the bars in the "free" or "down" position.
Even without the BAL X-Chock the "unwanted" movement in the trailer is reduced by about 90 percent. I sprayed all the mechanisms of the bars with CLP, wiped off the excess and sat down and took a break.
Once I figured out what I was doing... it took me about 4 hours start to finish.
The span between jack foot and opposing trailer frame rail nearly allowed me to mount the big end to the trailer frame, close but no cigar. If I could have, the foot on that end would be left on. I suppose you could lengthen the bar with pipe. If you decide to do it that way, the finished product would be much more stable. I decided the joist attachment would be OK... when you tighten the bar, you can see evidence that the floor joist is being deflected; where the frame won't move.