The following is transcribed directly from my daily notes as I developed the Test Mule into a working rig over several hot days.
July 16, 2007
The Test Mule is temporarily fitted with a handlebar for manual steering. Subjective riding will be done at three settings: #1 (0° rake and 2" trail) because of it's most-extreme setting at the high end, #10 (30° rake and 2" trail) because it seemed best in static testing, and #15 (40° rake and 5" trail) as the opposite extreme setting at the low end, Each ride will be the same (approximate) length over a set course (city street) and differences, as subjectively detected, will be noted.
The previous incarnation of the Test Mule was unrideable. Motorcycles and bicycles all steer via counter-steering and the Test Mule steering was designed incorrectly for direct steering. Two pulleys have been added to "cross the ropes" in the hope of simulating counter-steering. The foot-steering idea has been scrapped. The training wheels/outriggers are off. The knee-activated brake is not a foot brake on the right side. Until I can ride the damn thing while steering with the ropes, there will not be any true kinetic testing.
This attempt at testing, using link #10, was unsuccessful. Phil was here and took several photos. The cheaply-rigged steering broke during the first test. Very tough to get started. Very large turn radius. Lots of frame flex. Tried to steer via the broken handlebar shaft with lackluster results. No data on the foot brake conversion. The cheap steering crap was later stripped off.
July 17
Created new "hard" linkage for the test Mule. Salvaged many old pieces to act as new hardware. I'm ready to try the subjective testing again with links #1, #10, and #15. I'm leaving the rope behind. I think it'll be tricky enough as it is. I need to get some experience riding something so low, so long, plus need practice with the oddball brake. Will I be able to see the speedometer?
The test was a failure. The steering stem jam nut I made failed to hold the handlebars in place. I managed one brief coast (cautiously) and verified it will steer and brake works, but that's it. I tried using the kickstand as an aid when towing the creating, but it doesn't work very well. I need something which attaches to the index pulley and allows me to push/stabilize with both hands, kind of like a tiller bar.
Did some grinding to the jam nut and torqued it down hard. It appears (so far) to work... maybe. I used a hose clamp as a collar to adjust the handlebar height (or drag link clearance). I added little strips of cardboard between the steering stem and the outer tube to act as bushings (lots of slop). Last was a tiller bar to push the mule when heading back uphill. It also works as a kickstand, thus performing two functions from one crude tool. It's late afternoon and hot (100) so I will wait until tomorrow morning to test my changes.
July 18
First run with new handlebars. Very twitchy, over-sensitive with #10 link. Reached an indicated 17 mph. Some partial turns, mostly straight run. Handlebars still loose. Tiller/kickstand works OK. Changed link and pin to #1, readjusted handlebars. Could not see speedo. Ran pretty stable, not so sensitive. #15 link showed very heavy taking ff, wheel wanted to flop, but improved considerably past 10 mph, fairly stable, felt frame "hop" and flex, did slow turns, worked OK. Back to #10 for final run. After trying others and having a little practice, #10 felt better than at first. Jam nut still sucks, had to crank to near-breaking to hold together for #15. Felt more frame hop at some points. With last run did wide, sweeping turns, felt the caster/trail working, reached 17.2 mph. Brake works "OK" but at speeds this slow it works as well as it needs to. Need better steering linkages, need more practice, and soon will need a bigger hill. How to verify the speed? Need fabric measuring tape to measure the true circumference of wheel in order to calibrate speedo. Layer of duct tape around jam nut to increase friction? Must go back to measure start/end length. How to measure slope? Used my welding level, road appears approximately 3° of slope at the steepest (visually) point. The entire length of the run is 580' on a 34'-wide street.
July 19
Made a new jam nut from scratch with "wings" to help guide it upward and it seems to work, feels solid. made a cardboard "basket" to eliminate the dangling shopping bag and it looks good. Used corrugated cardboard strips as bushings in the steering tube. The re-stacked washers for the steering links seems to work better. I still need to calibrate the speedometer, but the rest of the changes are done and now it's time to see what works. Thankfully it's a much cooler day, showing 74° at 11:30 am, so the sweat factor should be lower. After further revisions, I'll try combinations #4, 7, & 13.
#4 (10°/2"): Stable, but wants to fall into turns, steepest turn I can to is 10-12°, 15° at most. Coasted straight to build up speed, then did the turns. Very easy to get started, new jam nut works, and must get better brakes.
#7 (20°/2"): Easy start, very stable, light return (didn't want to dive into turns), fun to turn, no problems, but lousy brakes.
#13 (40°/2"): Low, easy start, easy turns, felt "chopperish" but no flop, fun to turn, almost went too sharp (15° plus) and nearly crashed. Big sharp turns, fun to steer.
#10 (30°/2"): Tried it again, felt neutral, did not fall into turns yet did not have to be pushed into it. Turn effort easy, did not have to "pull" to get back out. Coasted home on final test, slow at 7 mph, steering felt unstable, as if no trail, could not let go of handlebars.
Working to eliminate rope in the brake system, must improve braking, and in the process broke a caliper right off it's mount. I'm re-welding the bracket and full-welding both sides, then using a recycled cable from the donor 10-speed's rear shifter. Considering the weight of the Test Mule, a front brake is not a bad idea, but it'll have to wait until the low-speed testing concludes.
July 20
Out in the shop at 7:05 am. Goal is to get the brakes finished, then establish a test course and methodology, as well as test the remaining combinations for the low-speed subjective testing. It's going to be damn hot, so I need to start early.
Starting at 9:20 am, first runs with new brakes. Link #5 (18.4° rake, 3.5" trail) seems stable, but I was distracted aiming for first-time turn points. Took some effort to turn, wobbled, when I took hands off handlebar. New brake works better. 2nd run with #5 was 40 seconds duration, seemed OK, some effort to turn but brief, only 5-8° turn (counter steer). Right handlebar hits right knee.
Goal achieved: full testing began at 9:30 and ended at 12:00. Brake worked much better, cable is better than rope, doesn't stretch, now must make more permanent version.
Total time for testing 15 combinations was 2.5 hours, or 150 minutes.
150 minutes divided by 15 combinations equals 10 minutes per test.
July 21
Made a longer steering tube to raise the handlebars another 4", which helps to clear my knees. Measured the front tire, 175 cm, and I think I was successful recalibrating the speedometer (which was set at 152 cm). It'll be interesting to see how it reads now. I also gave the steering links a shot of WD-40. Pumped up front tire from 20 psi to 35 psi and did the same to the rear: both tires now at 35 psi. Cut new shims for headstock bushings, made a tiny plywood bearing at the top for upper support: eliminated most free play in steering. I went around and checked/tightened all connections, screws, nuts, etc. The brake cable is now clamped tightly and all seems adjusted right. The beast is ready for it's next set of tests. I think I can do my measurements with the handlebars, holding with one hand while the other hand holds a scale and turns to measure the effort. I also see the steepest I'm turning is 15 degrees, yet in the static tests I went all the way to 45°. Perhaps redo the static tests with: 1) handlebars, 2) higher tire pressure, 3) no ropes, and most of all, 4) only turn 15°, then return.
Now I'm going up the hill to try #4, #7, #11, and #15 with new steering and brakes.
After several days and several sets of tests, it's easy to see just how subjective this kind of testing can be. Several of the same settings generated different response in the notes. Part of this can be attributed to learning how to ride the Test Mule, but the rest of the ambiguity and changing perception is the nature of subjective-only testing. Now that I have: 1) a set course, 2) the mechanical problems solved, 3) experience riding it, and 4) a better idea of which combinations to focus upon, I can begin trying to ride while also measuring the effort involved.