Search all of my sites with Google

Friday, February 20, 2009

More Yard-based Test Rides, Steering Problem Found

I finished boring out the steering tie rod eyes for the skate bearings, which didn't take long thanks to the lathe. Since the eyes couldn't be mounted in the chuck due to their length, as they would have hit the lathe's main beam during rotation, I clamped the vise to the tool-holder platform and put the largest Unibit in the big chuckholder for the tailstock. Then I took the tailstock's tube out (simply by cranking it forward all the way to unscrew it from the crank) and put that whole thing in the lathe's headstock chuck to hold it straight and centered to spin it. The eye went into the vise, and I just moved the tool-holder platform in and out to bore out the eyes to the same size as the bearing units.

It was a slightly loose fit, in that I could push them in and out with my fingers, and since I did not want them to come loose during steering, but also didn't want to destroy the bearing races by trying to weld them in, I decided to use my small butane torch (it's "pocket sized" and only holds enough to burn for about 20 minutes on medium, or maybe 7 or 8 on high) to heat the eyes and bearing units enough to solder them in place. Since the torch doesn't get hot enough to even melt the silver-solder I have, I just used regular electronics rosin-core solder, and scrubbed the outer ring of the bearing units thoroughly with a sanding foam block in hopes this would be enough to let the solder stick. The eye surfaces were just lathed, so they're nice new shiny clean metal already.

I clamped the threaded part of the eyes between two pieces of wood (since a metal vise would have just heatsinked away the torch heat), so that the eye was vertical and the bearing could not fall out or shift during soldering. It took a few minutes per eye, but it worked well, and in the ride tests later it did not show any signs of cracking or other failure so far.

In the process of reinstalling the steering tie rod with it's new bearings, I managed to crack away part of the aluminum handlebar-stem I had been using as the front end of the arrangement, but fortunately it was not the threaded portion I needed for this. However, it did take away the only stop the system had had preventing a full-on left swing of the wheel from "plunging" around and flipping the entire front fork direction 180° from what it should be.

Above is how the forward end looks at "rest" position in the center of the steering range. It's taken from directly above the forward headstock and the front fork. The tie rod is to the left, and the top tube of the Magna frame is near the center of the image, vertically.

Below is the point at which it becomes impossible to steer back from a left turn, and the wheel is stuck almost 90° from straight.

If I'm steering hard left, moving the bars fast, the momentum will continue turning the wheel past this point, and the pivot point will now be on the right side instead of the left, and I will be unable to steer anymore as it's almost locked into that position (only a few degrees of movement possible).
The video below shows it more clearly:
Pardon the shaking camera, as I didn't take time to setup a tripod for this like I should have.

I have a couple of ideas to fix it, both involving essentially a stop pin or plate that keeps the front fork from going past a certain point. Most likely I will go with a plate welded to the back edge of the fork's top bar, where it joins the steering tube. This will limit the max steering angle to about 70° or so to either side of straight ahead, at a guess (have to measure it to know for sure), and prevent the disastrous momentum-flip.

It will also give me a place to mount the front turn-signal/marker light units, which look basically like the ones on the rear of the bike (at the top of the seat back), but have angled brackets built-into them, with bolts integrated into the brackets. The angle of the plates won't perfectly match the original angle of the lights, but I can bend the brackets a bit at the end where the light is to fix that. They originally mounted to the front plastic leg-shield on the Honda Spree, which was angled back quite a bit to deflect wind around the rider's lower legs and feet.

I did about a quarter-mile of riding around the backyard in circle-ish patterns, testing out and getting used to the steering, now that it doesn't have any slop. The problem above nearly crashed me several times, so it's definitely got to be fixed before it goes on the road again. Other than that, the chain guide/deflector wheel works pretty well, though I can see enough wear on it that I'll need to find a more permanent solution if I don't get the motor on here soon. The chain is gouging into the wheel's plastic too much, since if I can notice a difference (barely) after only 1/4 mile, there's going to be severe wear after not too many days on the road if I do my usual riding with this bike, but without the motor on it.

With the motor, once it's attached, it will take most of the pedal-chain tension away, so the wear won't be much of a problem anymore. Then this wheel will just be the throttle sensor pressure roller and chain guide, and not have to take so much pressure from the chain that it gets chewed up.

One nice thing about this bike seat being where and how it is, is that I can easily just put a foot down to stabilize the bike if I start to tip too far or skid or whatever, and generally prevent any bad stuff from happening at lower speeds. At higher speeds, if I have time to brake enough to shed speed I can do the same thing. Otherwise, the only difference it makes is that I have a much smaller distance to fall, and I'm going feet first instead of head and hands first, so I tend to just roll and skid a little, which didn't even tear the pants or anything, in the more-than-a-dozen crashes I had (mostly due to the steering problem above).

On the upright bike in a similar type of crash due to locked steering or being unable to make a turn due to high speed, the bike slides out from under me or flips taking me with it, usually landing me on my hands or shoulders if I have no time to begin a body roll. Both of those kinds of landings are a lot more likely to break something or injure me in other ways than the skid landings I'm getting with this new bike.

Until I can really test at higher speeds (like on the canal paths both paved and gravel, where there's no traffic to run me over after I crash), I won't truly be able to compare the lifetime of experience I've had crashing the upright-style bikes to the few minutes of riding and crashing this one, but so far, at the 5-8MPH and lower speeds I'm getting up to in the yard tests before I have to start a turn, it's way better on this new one. ;-)

Since today it had been relatively warm and dry all day (in the mid to high 70's in the afternoon), then when I finished with all the work today, near sunset, I primered the bike to keep it from rusting at all the places I've done paint- and surface-damaging work and modifications, since it has been raining so much lately.

I didn't have enough of any one color spray primer, so I used the lightest colors I could for most of it, and the least-blending-in-with-background color I had after the light colors ran out, especially over the areas with the roughest surfaces and the most hard-to-reach crevices, like the rear part of the steering assembly, and the top and bottom of the kickstand. Those got purple. It's not really primer, but it'll keep the water out of the welds and cut/ground-off areas.

Most of the primer was an off-white, which turned almost tan on the rubber of the tires. Painting the tires a light color makes the bike MUCH more visible from the side at night, even without lights. Compare the side views above with the one below, which although it's in daylight, and the seat is lighter-colored (not yet covered with the brown vinyl) is still clearly less visible than the light-colored tires above.

The light-colored frame vs dark-colored frame also makes a difference, but the tires are large and round, and the eye (brain, actually) does see such objects "faster" than others, at least for me.

Later, once the bike is actually "finished" it will still probably get the DayGlo Avenger paintjob. However, I found some old (very old) cans of Pactra RC-Aircraft type paint in my stuff when I was digging around for the primer a few days back, and though the thinner/carrier in it has yellowed significantly, it is still usable. I tested it by painting the lids of the cans, since the original color samples printed in ink on the labels have all faded a lot in 15 years. ;-)

Surprisingly, the paint dries as it should, and sticks well. It stinks very badly, and I have doubts that whatever was used in it would be allowed these days. :-) Definitely outdoor-use-only stuff. There's four colors, plus some "clear" that is more like aged-lacquer-translucent-brown now. Tropic Blue, a bit turquoise-tinged due to the aging carrier, is a fairly bright color. Darker but would still stand out is the Sunset Orange, which is more rusty-amber color to me. It's a bit redder than Loki's fur in the bike pic up above. Strobe White is more beige from the carrier, but still good enough to use as a white reflector underneath the DayGlo paints, or for white trim anywhere I might want it. Airframe Aluminum is your average slightly sparkly silver paint, not apparently affected by the carrier's color change.

I am considering using these, along with my airbrush, to do the final paint job on the bike, using the DayGlo Avenger colors only for parts of the bike here and there. It would look pretty nice, and these are tougher paints than the crappy Rust-O-Leum junk I still have for the DayGlo stuff.
I also found some old dried-out poster paints that include several DayGlo colors, and am thinking of grinding up some of them and mixing with the Strobe White in some separate jars to do small bits of DayGlo here and there without having to use the crappy Rust-O-Leum sprays (of which I don't have enough Orange, anyway, and no Yellow). I've never done this kind of mixing of pigments from other paint types together, so I have no idea what the result will be until I try it. :-)

No comments:

Post a Comment

Alternate suggestions or improvements to anything that's been posted is very welcome, and extreme detail is preferred to brevity.

Keep in mind that unless you leave an email address in your comment, I haven't any way to reply to you except to reply to your comment here. That means if you want a reply, you'll have to come back to *this* blog entry and it's comments to see my reply to you, unless you leave some method of contact within your comment.