Gravity racer - Calling all daredevils!

[chubs68]

i think im gonna join in with this, its gonna be my first build off. ill post a pic later.

[breakurnees]

I just got the tires on and kneelers built. I took it for a ride down the driveway brakeless. Oh boy it is gonna be fast! The steering is twitchy due to the rake. I also scrape my butt on the tire a lot. I may have to make a seat. 35 won't be a problem, not doing 80 or crashing hard might be tricky.

[Three-Wire]

Took a night off from chores to get some work done. Call it a mental health evening...

Got the majority of the frame work done. Still some tweaking to be done, but this is the basic layout... I need to add a member where the red line is drawn.


To keep the pivot point locked into the dropouts of the purple frame, I had to fab up some plates that have a hole for the new pivot bolt.

For steering, I want to put the MTB bar ends on the tripple-trees like I've seen done elsewhere on this thread but I can't make the pair I have fit. Still thinking about alternates for that...

[aka_locojoe]

Well, you guys have inspired me... The Coaster's are hosting a Gravity Shoot-Out in a few weeks and I thought it looked interesting, but Philphine's, Fej's, and Snydur's bikes along with Snydur's experience put me over the edge. I'm in. May not get to run it until after the deadline, but we'll see.

I don't have the gear or time right now for welding, so it'll all be bolt-on stuff. We'll see how my ideas for that play out.... Here's where we are tonight:

Cool. I hope you get it finished in time for the race. See ya there.

[Philphine]

the bar ends i put on didn't fit either. it's one of my later worries, like if i stressed the metal bending it out or something.

but on one set i just stuck a screwdriver or something in the screw hole and bent it out. on the second pair i had a seat post that was i guess 7/8" at the top, but fit into a 1" seat post hole. so i stuck them on the seat post and hammered them down till they expanded onto the 1" part. then i drilled out the old bolt holes (couldn't get them to line up again plus the old bolts were then too short) and added new nuts and bolts to tighten them down.

like i said, i can't say it's 100% safe. seems ok so far.

[Three-Wire]

Cool. I hope you get it finished in time for the race. See ya there.

Thanks Randy. We plan to be there... My wife is gonna ride her 'Lil Chick - first time she's been on it since she was a 'lil chick. We'll take off the chain and put on caliper brakes just for this.

the bar ends i put on didn't fit either. it's one of my later worries, like if i stressed the metal bending it out or something.

I suspect you'll be ok, but if you're not confident in it then I'd find something else to try. Tonight I gave up on the bar ends and just flipped the bars that came with it. This should work fine but I may try a different stem, bars, and brake levers from an old 10-speed.

Tonight's progress:




Extra member is installed. Frame is very rigid with the extra member and pretty heavy. Now, I've got to figure out how to ride it! Not sure how to sit on the thing... I also have to make retainer plates for the rear wheel, similar to what I fabbed for the pivot point. And hook up the rear brake, true and overhaul the wheels, ditch teh reflectors, and install a bald set of 60psi 20" MTB tires... One more complete evening out to do it.

[breakurnees]

Witchita is a long haul from here, but it would be fun to race a fellow member. Hmmm...

[Philphine]

Tonight's progress:



Now, I've got to figure out how to ride it! Not sure how to sit on the thing....

how wide are those two pieces of angle iron? maybe just a pad bettween them on top? the occ chopper seat i started out with wasn't too bad, if you have one and/or don't find something else. i switched mainly 'cause it wasn't working with my kneeler plan (plus since i was kinda going for style, i didn't like how it looked as much as the one i used). it would bolt right to the two pieces (i think, just going by the pic) and also give you a little flip up in the rear so you don't slide back to the wheel.

[Philphine]

well skip all that. i forgot you're using the x-games bike. if you have the seat from it you ought to be able to get it to work well enough.

[breakurnees]

I have brakes! Tomorrow I have to work out better pads for the kneelers, a seat and weight. I hope to do some real test rides tomorrow night.

[breakurnees]

Careful out there guys. I should be getting leathers and a helmet this week, but I was feeling bulletproof and ran my bike down the driveway with shorts on. Now I am missing some skin on one of my knees.

[Three-Wire]

I was in Creede, Colorado over the weekend and spotted this:



A little different than what we're building, but still interesting.

[Philphine]

i can see it. push everything down for aerodynamics going down, pull it all up to pedal back up the hill.

truthfully, i picked this up for a compleatly different type of bike, but it could make a nice downhiller if you could keep the drivetrain to pedal back up.

[Three-Wire]

Did a little work tonight... It's almost ready to run, but lots of little things still to do. Like rear brakes... And different tires... And truing the wheels and brake discs... And figuring out the final solution for the foot pegs... And adding balast... And maybe some paint and cleanup?



It certainly could benefit from a fairing of some sort. If I can find the time next week, I've got some relatively easy ideas for a quick and temporary fairing.



With me on it, the proportions look more appropriate but still I think a fairing would do wonders for the overall appearance.

I may get a few hours to mess with it on Sunday - if I can get the brakes and tires done (and scrounge up the right P.P.E.) I'm gonna try to go test run the thing down the local hill!

[Philphine]

well, it looks fast, anyway.

probaly no aerodynamic benefit to it, but i added a bit of lexan to the numberplate from the x-games bike for my second bike



i also used a squeeze clamp thing and propane torch to give it a little more curvature, maybe too much

i have a second numberplate i may put on my real g-bike attempt (assuming i ever get more speed/riding in on it), but i want to learn more about how to shape it to maybe get some genuine results from it.