Gcrank's 'Flat Out Racing-Gravity Works For Me'

[MplsCoaster]

Hey Everybody,
Gcrank1 sent me some pics today of his cool build. I'm helping him out by posting them for him
His email to me started: A 59 yr old grampa of 3 doin' goin' for the brass ring!.
Awesome Dude!
The bike

The trip:

The hill:

The Run: He's ready

He's set

He goes!!

Great job! Looks like fun! Congrats Buddy!

 

[kingfish254]

You should call it Newton's Apple!!!!
I love it!!!!!

 

[gcrank1]

Thanx MC for posting these!
Ive been calling it Morph the Death Bike......and 'Flat Out Racing' - 'Gravity Works for Me' is intended to go on my poster and or 'tank'.
Morph because it has just been morphing into what you see, sorta took on a life of its own,
and Death Bike because a good friend called my new 'adventure "downhill coaster death bike' runs.
My oldest G-son, Cassidy, now 20, gave me the bike after I told him Id seen some cool U-Tube videos of gravity bikes on mountain roads and I thought it would be fun, but the BMX bikes they built from were too small (Im about 6'1" x 210ish#).
This rig kinda 'fell together' in the last two weeks after some thinking about it over the winter. The key was finding the MoZo tele-fork (thanx RatCycle) to replace the raked & extended front end, and the 20" BMX wheel to level it out more. Other bits & bobs, like the BB mod to get me pegs were just the last couple of days. I still might go to a 26" so I can put some canti brakes back on the front, but the big OCC rear brake works great.
That little hill we call 'The Wall' because when we pedal the uphill way it looks and feels just like a wall. My wife didnt pace me, but she got 40mph out of the car on a coast, and it felt about that to me on the bike (40 + yrs of motorcycle ridin' to judge it). I was movin' pretty good because Josh, my youngest G-son at 16, gave me a good push off. The total distance was 4/10s + of a mile. As a shakedown this was a total success, and we have much longer and faster hills here about. The bike with this rake and trail isnt twitchy at slow speeds and very stable at speed.
Im gonna document the runs and my wife will do a digital photo show.
This is my first 'real' ratrod build.....ya'all been an influence on me
BTW, my first insane g-bike run was in 2003, at 50, when I rode one of those kids little kick-bikes down the biggest hill in town (called hospital hill); you know the one with the tiny wheels and a pivoting rear fender for a tire brake. My wife paced me with the car and I got an honest 20+ mph before it got 'unstable' and I decided to brake..........that rear was smokin' and my heel getting hot before I scrubbed off enough speed to be sensible! I no longer recommend that platform for a g-bike! :wink:

 

[aka_locojoe]

Cool. Wonder if he clocked himself?

 

[kingfish254]

I notice you said we have been an influence, but you didn't specify whether it was a good or bad one!!!

Cool story and cool bike !!! Bravo!

 

[FatBoy]

Sweet Build! You have to be the coolest Gpa in the neighbor hood! 8) :mrgreen:

 

[Skipton]

Great stuff thanks for posting it MplsCoaster

gcrank1 cool bike looks like a lot of fun! ....extra points for the cool outfit :mrgreen:

You should call it Newton's Apple!!!!
I love it!!!!!

:lol: :lol: :lol: :lol: :lol:

 

[KJV]

seems boring, to me;coast down a hill. :roll:
now, pedaling @ full crank, down the hill. :arrow:
well , the gravity thing would be a blast..
down a winding mountain road. :mrgreen: 8) :!:

 

[gcrank1]

Ive got some hills in mind here that will be anything but boring! One rodie told me he got 60mph on one of them; down low, tucked in and nose out front on this bike will be 'interesting'....... :shock:

 

[SCHWINNRAY69]

That's a COOL looking chopper 8)

 

[fast eddie]

i love it !!!
fast eddie

 

[Philphine]

i like it, i also like that you tried the big occ tire. my second g-bike has one but i never ran it. i was told it would probaly be slow but 40 or so would be exciting enough for me i think.

 

[gcrank1]

Thanx guys! At this point that bike is still 'reversible', but Im thinkin' there isnt much reason to be, it will never be worth anything more than what it can be made into.
I mounted a mid pressure Kenda on the front right away, rated 40 -65psi, and bumped it right up to 65. The slow rear I know is a 35, but I did 40psi (thinkin it would be OK?). There is no room problem if I decide to go with a narrower rear wheel/tire combo, just spin some spacers on the lathe. I think more hill will overcome a lot of that slow rear tire, and Im going for the fun factor ludicris speed rather than 'termiinal' velocity.
That hill is a local 'roller coaster' with a substantial drop just off the crest, so I gathered speed quickly after the push off. I knew I could dawdle by grav alone and paddle my feet to get going, but that wouldnt have shown me if the bike worked at speed, so I went for it.
The footrests with the flipped crankarm are a compromise, and free, just for shakedown. If I had enough axle threads to really give me confidence I would have screwed the pegs on back there, but the thread pitch was wrong, and I used a set of the Mongoose trick bike's chain adj. plates as rear axle stops to keep the wheel squared up and off the brake cable up front; just push it forward and tighten down now (works really well!), so there arent many threads exposed anymore.
I might get a bigger hill run yet this weekend :shock: .

 

[gcrank1]

After thinking all day (after reviewing the 'Daredevil's thread last night) and doing other non-bike stuff I had some time. I mounted the Mongoose trick bike's bars inverted and out front a bit to get more reach (doesnt look near as good though) and dropped the crankarms. The big chrome trick pegs are now on the rear triangle, down low, but a bit forward of the axle. I have to leave the saddle that high as I am not as 'flexible' as some of you young chaps, but I can get on the rearsets and really get a stretch out. My chin is right above the bar-stem clamp now (and I'll be lookin' out the top of my eye sockets!) The weight front to rear should be improved and I mounted some barbell weights at the BB as appears to be common. At 68# thus far it is a bit of a chunk to load on/off my car 'wheel' rack, pretty close to the max of 75#. More weight means more load on the brakes and longer stopping distance too.
Its ready to go tomorrow, if I get time, and today we scoped out some fantastic (FANTASTIC) hills I have had in mind. One is 4/10ths of a mile ALL downhill on a pretty good grade, the other about 7/10ths on a killer grade!!! Maybe I can have MC post the MkII Morph and the proposed runs; I know you guys in Kansas will be green, and not because its St. Pat's Day!
As we used to say in the 'club," shiny side up".......

Update: I ran the 'bunny hill' again today once and the weight distribution and leg/foot position is better, Im not too sure about the long reach and 'tiller' effect that far out from the headtube, though many of the g-bikes seem to have it that way. Speed gathered quickly with a downhill rolling weight of 275ish # and felt more like a small motorcycle beneath me.

Update 3-21-'12: Ran the hill again to feel out some changes and my wife followed with the car; she says an honest 35mph plus, but didnt make 40 (but hey, I guessed pretty close!).
Heres the MkII version:

 

[MplsCoaster]

The setup never quite stops (for me too). Looking forward to some new fun on hills!

 

[gcrank1]

Here's the go to that got me all revved about these:
viewtopic.php?f=43&t=41784&st=0&sk=t&sd=a&start=165

 

[gcrank1]

Geesh.....these things are addictive too!
Morph had a flat front tire today.......and I had a nice, long, new hill to try within 6 mi. of home on a lightly traveled town road. No new/spare tube in the place or even a patch kit......
So I pulled out G-Bike No,2; a Huffy Cranbrook that still has the crank (so I can pedal UP the hill, too?), roadbike dropbars and a setback & slammed banana seat. It is surprisingly comfortable. But the best part is the Bontrager H-2 high pressure tires, these at 80psi, and they FLY. I talked my wife (somehow I think she has only reluctantly subscribed to this new passion) into pacing me on run two, and she says it looked like I got just shy of 45mph.
Hey, ya'll, this is about as easy as it gets to get into G-Bikin' !!! I know it doesnt meet the 'sanctioned' rules (20" or less wheels, 50" max wheelbase, 75#), but there aint no sanctioned race here!
Im gettin' that flat fixed and running Morph asap to see how it compares. If I can talk a bud into it I may even get a S x S run........ 8) .

 

[gcrank1]

3 pm ish today, ran Morph with the new tube down that big (.5 mi. drop) hill and my wife says it was an honest 45mph plus, maybe pushing the 47.5ish mark. Bike ran super, nice and stable, and the weight under me definitely feels more substantial at speed than the Huffy. I can see that breaking the 50mph mark is going to take some work, or BIGGER hills!

 

[kingfish254]

GC, did you ever see the photo of one of the early mock ups of Fugsley? I bet a Dahon would make a decent platform for a gravity bike.

 

[gcrank1]

I can see potential there, but since BMX, and other more available platforms are so cheap and readily available, it might be better used more as intended? (but then whats the fun of that?). My practical side always argues with my 'dark' side........
After watching some of those Aussie videos I cant believe how low those riders get! For me I cant get my butt too low or I cant bend my knees back to pegs without cramps, and/or my knees too close to the ground, and then if Im stretched out too long I have to support too much weight with my arms (no chest-rest pad) and I cant crank my head back far enough to see; lots of issues to get a reasonably comfortable fit for a long run.
I think if one ignores the wheelbase 50" 'sanctioned' rule and makes a long frame with a high enough toptube to put a chest-rest on that you might have a goer (but Im a new study at this), more of a drag-bike look? I see FastEddie has quite the 'chair' on one of his, and I see the sense in it now. Rules?, what for?, lets build RRB G-Racers!
You build that Dahon, K-Fish, and see if you can beat my 45mph (so far, but goin' for mo :wink: )........
PS: Im thinkin' that for safety Im going to mount an LED front flasher and maybe get a marine can powered fog horn, or such, if I can figure a way to activate from the bars. It might just get somebodies attention that otherwise wont really see a G-Bike coming.