| 20/20Hi This
is pretty much the same animal as the 20/20 Heavy, but I wanted to spread out
the handlebars a little to open up the cockpit. I also wanted to put the
seat rails on the inside of the frame rails instead of the outside so that a rear
wheel quick release could be used for quick seat adjustment instead of using nuts
and bolts. I also used the new style seat with the more open angle at the
bottom. So, with the few small tweaks, the "i" in the name can
stand for "improved". . . groovy, eh? :)
| 12 Nov 2007 I've
been at this trike on and off for quite a while, but finally got motivated again
over the last couple weeks. With a busy schedule, I still managed to devote
at least a couple hours a night to it and about for or 5 hours per day over the
weekends. Fleshing out the big parts is easy and it goes pretty fast, it's
all the fine details and little bits like tabs, cable stops and steering pieces
that takes the time. At that stage, the slow visual progress gets a little
frustrating. But, it's slowly nearing the end. As a side note, I finally
actually weighed the complete frame with all the steering bits, but minus the
seat, and it weighs 14 lbs. The large EMT tube seat weighs 4 lb including
mesh. | | | | | | This
is a close-up (crappy one) of the small brake mount I use in various forms to
mount the rim brake calipers. The small "T" piece is made from
a section of ½" x .063" square tube, and it's welded at right
angles to a piece of ½" x 1¼" round stock with a ¼"
hole drilled down the middle. The alignment process is pretty low-tech.
I bolt the calipers to the small "T" section and point it towards
the handlebars with the wheel mounted on he steering arm. I use a piece
of 1" square stock to act as a spacer between the brake adapter and the tire
to set the proper distance and leave enough space for a fender later. I
make sure the calipers are centered side to side on the tire, and eye-ball the
caliper legs to make sure they are pointing at the axle, and then I tack it. Check
the alignment, apply a couple love taps as necessary to line things up, and then
add a few more tacks. Then, I pop the wheel and caliper off the steering
arm and do the final welds. The picture is prior to weld clean-up. | | | | | | To
the right is thge finished steering arm. It's made out of ¾"
x .063" square steel with a 7" section of 7/8" handlebar tube welded
to the end. The ¾" tube is more than strong enough to support
the weight of even a 260lb rider lowering themself into the seat. You can't
really see it, but the handlebars are offset to the outside about ¾"
from where they are normally linied up with the kingpins. The small flat
tab on the inside of the steering arm is where the tie-rod bolts onto. The
hole for the tie-rod is about ¾" in from the kingpin axis and this
gives it some Ackerman compensation. How much compensation? Don't
know, don't care. :) Honestly, for the homebuilder, it isn't important to
do a lot of fancy calculation because it isn't possible to have "perfect"
Ackerman compensation anyway. All you can do is set it up for best guess
at the amount of steering deflection it will spend most of its time in. Anything
outside that, and you'll get a little scrub anyway. Even expensive trikes
don't have "perfect" Ackerman compensation. My main point is though,
most of the time, even at low speed, when you're turning, the inside wheel is
starting to un-weight so extra tire wear is pretty much a moot point. Screwing
up the toe-in setting eats tires WAY faster than Ackerman compensation that is
off, so I say don't sweat the Ackerman. | |
| 18
Nov 2007 And here it is finished. It
doesn't have my preferred quick powdercoat job on it because the place I normally
go seems to have either gone out of business, or (hopefully) business was so good
they moved to a new spot. Another powdercoat shop would have added at least
another $150 to the cost, so for this one I just used some gloss black Armour
Coat spray bombs. Crappy paint though, so next time, I'll go back to Tremclad
like I normally use. I also added a picture of the boom folded becuase it
looks sort of weird, I think :) I went for about a 10km test ride, and it
turns really well, runs very smooth and I'm very happy with it. This one
I didn't test ride at all until it was all finished. | |
The specs are the following:
| Length: | 74" |
| Height: | 24" |
| Width: | 31¼" | | Track: | 26¼" |
| Wheelbase: | 40" |
| Seat height: | 9½" |
| BB height: | 15½" |
| Ground clearance: | 4½" |
| Caster angle: | 15º |
| Seat angle: | 38º (adjustable) |
| Turning circle: | 13' |
| Weight: | 45lbs |
| Front wheel: | Alex 303 Al 20",
14mm 48 spoke | | Rear wheel: | Alex
303 Al 20", 36 spoke, 7 spd freewheel | | Gear
inches: | 16.47" - 87.27" |
| Weight bias: | 60f/40r |
Next time I'm going to modify the
steering arm angles a little and have them drop 15º coming back off the axle
housings. This will allow me to put the tie-rod through the frame where
it is away from the seat and legs and has more protection. Main |
