Gravity racer - Calling all daredevils!

[breakurnees]

This is what I started with, a Next full suspension bike that some one had put a springer and a set of apes on.

Here is where I am now. I can invert the apes, or bolt on MTB bar ends. I was hoping to stay full suspension, but the shock doesn't expand, it only contracts. If I swing the frame all the way open, it ends up at a 48" wheel base, so I may just work out a solid link that gives me the max workable wheelbase. I can't imagine trusting my life to a spring that I made to fit in there.

Kneeler, weights, seat and brakes still to come. Oh, and tires.

 

[Philphine]

S1

is this bike right at 50"? how tall is the rider? thanks.

hey, and also. has anyone ever used a schwinn occ rear wheel? is it not firm enough to be worth getting the extra contact patch. i might have tried it if i had thought of it sooner. i may anyway 'cause i still have plenty of 20" parts.

 

[breakurnees]

I would think the OCC tire would be a slow roller. How much pressure is it rated for?

 

[S.I.N. CYCLES]

@Philphine: I believe the wheelbase is 48" and I am 5'11".

 

[snydur]

I would think the OCC tire would be a slow roller. How much pressure is it rated for?

35 psi i would think there would be to much friction because of the size of tire.

 

[snydur]

006 by andrew snyder, on Flickr
different brake cable is on its way

011 by andrew snyder, on Flickr
he's the fastest turtle in the west. and he serves a purpose, hes held on with a long bolt, and it also hols the weights and tubing in place. so its almost there :mrgreen:

 

[Philphine]

@Philphine: I believe the wheelbase is 48" and I am 5'11".

ok thanks. glad i thought to ask because my frame isn't as long as i imagined at 49-50", and i won't be able to use the rear axles as footrests (with suspension that seems like a good way to crack both ankles. i think i'll be trying running bars parallel to the chain stays to hold foot rests.

i may try one with an occ wheel anyway. i just like the idea.

 

[Philphine]

first side of the triangle

seems like it would be hardest, but actually the tubes connecting the front and back are hardest

and a planned seat

from looking at the instructables bike (which has become my ergonomics example, being as i have a similar wheelbase and i'm the same height). the seat has a similar look and the angle should work for it (and i have 2-3 of them 'cause they're not good for much else). also thinking about the occ wheel made me remember it. i think i have a way to suspend it over the spring, but i need to finish the main frame first.

so trying to work out the triangle, it ought to be downhi... er... i mean... easier from there.

 

[MiniMe]

slow............. ive done 45 on my mountian bike.

WOW!.With knobby tires? :shock: ..Clocked?

yes

 

[Philphine]

well, if nothing else, it looks pretty fast

got front and back lined up pretty decent i think. i don't have a frame jig. the few times i've tried making one it came out more crooked than the bike. the wooden one in the first pics is only good for getting ideas together.

the seat is next. i mean to run the spring through a tube so the seat can sit over it. the tube isn't as big as i'd like, but it should work if i careful lining it up, and in the end should probaly look better anyway. like it was fit to the shock.

so, reading and looking at the knee perch things and working on the seat.

 

[Philphine]

more questions for the experienced.

i notice on the s1 vid it looks like theres as much weight on the knee pads as the seat during the ride. on other bikes that dosen't look possible, at least not without some sacrifice to the knees. being able to support yourself on your knees is a good thing? ....



alright, minds out of the gutter :x



and the rear foot rest. some have their feet wrapped over them, some have them under their feet. does it matter, or is it just how the frame happens to fit a particular rider so they set their feet however they will reach? seems like being able to stand on them would be better, but since i've never made one of these i don't know.

since i need to make both i figure i'll try to make them in whatever way works best. thanks.

 

[snydur]

more questions for the experienced.

i notice on the s1 vid it looks like theres as much weight on the knee pads as the seat during the ride. on other bikes that dosen't look possible, at least not without some sacrifice to the knees. being able to support yourself on your knees is a good thing? ....



alright, minds out of the gutter :x



and the rear foot rest. some have their feet wrapped over them, some have them under their feet. does it matter, or is it just how the frame happens to fit a particular rider so they set their feet however they will reach? seems like being able to stand on them would be better, but since i've never made one of these i don't know.

since i need to make both i figure i'll try to make them in whatever way works best. thanks.

i think the foot part is just what fiuts them. my feet hang over the top (and drag a little to be honest) but my friend who is half a foot shorter has his feet on them

 

[Philphine]

this idea just came to me, and i'm glad it did

the tube i had found to run my shock through was a close fit. i cut up an old brake cable housing and stuck it in around the shock and it kept it lined up straight through the tube, good thing too. the way i was doing it before would have left it cocked. it might have still worked but this way i know it works fine.

i had my camera in my pocket wheni left for work so here's the seat/shock area compleat

not the prettiest, but it all lines up and the shock clears and works. i've got the seat on and even gave it a clumsy push and ride down the drive when i got home (still no place for my knees and feet), but i'll wait 'til morning to get a pic.

 

[Philphine]

seat on, some roll pins added for rear brake cable guides, brakes hooked up, and the beginning of trying to work out the knee and foot part

from making sure i got the tube around the spring right, i got the seat on kinda crooked. that should be an easier fix than if i had to rework the spring tube though, so i'm not too worried about it. i'm kinda beginning to not like the seat anyway.

the roll pins fit the size of brake cable just right. i've used them before. both wheels aren't too true and i can't center the front brake so they're adjusted out pretty loose. minor tuning fixes for later.

the kneeler/foot rest thing is making me think some. up 'til now the bike has almost built it's self, but this part i'm still a little fuzzy on. the tube hanging down will be for the knee part. i cut it longer just to make sure it wasn't too short. i think going by the first few rough measurement i'll be cutting 3-5" off.

this is my kneeler idea for now

some 5" pipe i cut in half. i plan to put it on with no padding, then find some kind of knee pad i'd wear myself instead of attatching them to the bike. it's kind of snug so i guess the pads can't be too thick. if i get it done i'll see how comfortable that is. also, from looking at you-tube vids there was one group who put a knee down in corners. i don't think i'd be as serious as that, but if the knee pad thing works with some hard pads (like skatepark pads) that might be an added bonus.

i do most of my welding at work (got a little harbor freight welder but i just don't seem to be able to get good with it. at best i tack up things and finish them at work), and i'm thinking through this kneeler thing so i probaly won't do much more over the weekend.

 

[breakurnees]

It seems to me it down to where you can put your weight. If your riding position is one that lets you sit on the seat comfortably, then you can put your feet on the pegs and hang your kneesliders out around corners (no kneeler required). If you build a solid kneeler, you put your feet over the pegs and put less weight on the seat.

 

[Philphine]

yeah, i guess because i don't really know what i'm doing, i don't have a good thought process for it.

i'm thinking it would be good to be able to stand on the pegs if i want, along with being able to put my weight on my knees or the seat. like needing various options during the ride. i've kinda given up on being able to stand on the pegs. since i don't want to put them on the back axle they need to be suspended back there somewhere. i think i have that idea worked out, but i don't know how strong it would be if i did more than just hang my feet over them.

still thinking though, and since light weight doesn't seem to be an issue with these (i'm up around 30lbs already. i don't plan to add weights) i might figure out something.

still building...

 

[Philphine]

seat change

what was happening with the schwinn seat was, when i started working on the knee part the seat was so wide and bulky i couldn't bring my knees together comfortably. so i dug around and found this seat. since i had gotten the other seat's mount crooked anyway i'll probaly cut/grind it off and just make a new one for this. the spring tube is mounted solidly enough that i can take all the seat part off and just concentrate on getting it straight, where i was trying to get both right together before. i want to change the new seat's position some anyway.

that postpones the knee part, 'til i know the new seat position. i'm still fumbling with the idea anyway.

that initial flash of imagination is about gone, but i'm pretty happy with the start so i guess i'll eventually figure out the rest.

 

[Philphine]

kinda ugmacious, but it should do

ground the old plate off and got the new one straiter. also moved it back a bit

a mistake i make a lot though. since i weld mostly at work a lot of times i just take the parts i need to weld. then when i get home and put it together i see something that doesn't work or fit like i wanted. i meant to angle the back up a bit higher, but i think i can add some spacers or stacked washers to the rear mounting bolts and adjust it some. being able to adjust might come in handy.

i'm glad i backtracked on the seat. i can now touch my knees to the bar hanging down for the kneeler part, so the kneeler can be narrower now. that should help both structurally and aerodynamicly.

still thinking on the kneeler part. the seat improvement is actually slowing that plan down 'cause i want to take advantage of the new positioning, but i think i'm close to starting.

 

[breakurnees]

Not sure anyone plans on buying tires for this, but if you do, tires that come in standard increments (20X1 1/8) DO NOT FIT bmx wheels.
I learned the hard way.

 

[Philphine]

you can go down to 1.5" and still get it on a regular 20" rim. i got one for another project recently.

edit: i should have added that's the smallest i know of myself. i don't know if there's something made bettween 1.5 and 1 1/8 that might fit.