frame dimensions???

[neophile]

I've just started looking into the stretched cruiser scene, and I like it. I've been looking around a lots of different options, seeing lots of things I like, but not finding the perfect look, so I want to build a custom cruiser instead.

I talked with the guys over a firebikes, they do some very cool bikes, and they'll build me a custom frame to my specs, but I'd like to try and do it myself.................I've got a buddy who runs a shop, so I could get the fabrication done for cheap.....I think, still haven't talked to him.........but I don't know what the critical measurements are. Figure this could be somewhat important, since it does need to be rideable.

Please advise on what I need to know before I begin shaping tubing, ie, distance from pedal to seat, how far forward can the pedals go and still be a comfortable ride? I can imagine you may end up in a position where you are forced to lean too far back and riding becomes a strain. How about ground clearance?

I'm looking to build something more along the lines of the skulls and spikes bike that Viking has posted in this forum: same kind of aggressive stance, but a different frame design.

I appreciate your thoughts and feedback, very excited about creating something cool, think it would be much more rewarding than just buying a new bike

Here is a very quick rendering I just did while sitting at my desk, don't beat me up for the glaring design flaws, most of them I think I know of........ie: the front tire is too close the the crank The ehight is off, the bike will be lower, longer looking, but I dodn't want to spend a lot of time redrawing it right now.

The bike will feature 1.5" tubing, 24x3" wheels, 3 speed hub with stick shifter, fixed seat, triple crown shocks (with a good bit more of a rake than is have shown in the image).

 

[pvwacko]

check out my build... might be a good reference for you. you will need at the very least some sort of frame jig, a tubing roller, welder, hole saw... What's your leg length? I'll measure my cruisers and see what kind of ratios I'm running.

viewtopic.php?f=37&t=20553

 

[neophile]

Good looking ride, I like the flow of your frame. Nice color scheme, similar to what I'm thinking of doing; all red wheels, white wall tires, flat black frame, with either white or red chain (not sure how white the white chain will stay).

I noticed in your build you mentioned you were using 1.5" tubing, with 3/32 wall thickness, I assume that is steel? Anyone use aluminum? I'm thinking this would be nice, keeps the weight down a good bit.

Here is a better rendering of the bike, drawn to scale. I have the seat set 27.5" from the center of the bottom bracket, I based that on my mountain bike, figured that should be the same. I'm 5'8" tall, leg length of 32".
Seat height is 21.5" from the ground, and a rise of 12.5" to the handle bars, with a reach of 18.5" to the bars. The top bar is 28.25" to the ground. Distance of 64.25" from axle to axle, 41.5" from centre of bottom bracket to the rear axle. I gave 10" from the centre of the bottom bracket, to the ground, and the lowest point, just in front of the rear wheel, is about 3.5" from the ground.

 

[pvwacko]

Looks good! My frame is steel. I don't really notice the weight of cruisers as much as I do road or mountain bikes. one of my first builds weighed in a 50lbs. I'm not sure how well aluminum will do with just a single rear stay... but I don't work much with aluminum but it may crack at the welds with much flexing. you may be able to hide some gussets to strengthen it up. As for dim. With my full sized BMX crank arms and my bottom bracket 11" from the ground it makes turning a little tight. usually I just don't pedal through hard turns. if you are using a shorter crank then you will probably be fine. for positioning the bottom bracket vs. the seat. my bike is about 28" from the seat pan to center of the crank. I'm 6'2" with a 35" inseam. my more upright chopper cruiser has a 26" measurement.

 

[neophile]

Appreciate your reply, thank you.

I have been wondering about the aluminum thing, will def have to think it through, more. I was worried about the single rear stay, but it's integral to the look, so I may go steel to ensure a solid build. I'll run it past my buddy, he's the machinist, hopefully he'll have a better idea of what to expect from the aluminum tubing.
Flex is a bit of a concern as well, I am running fairly low clearance in the back, if the frame flexes too much, I could have some issues.

Thanx again, Ill post some follow ups as things get going.

 

[neophile]

My machinist buddy had an idea instead of aluminum, titanium. Light weight, super strong, and you can weld to steel so I can use prefabricated bottom and head bracket. Sounds perfect, definitely solves the concern about the strength of the single rear stay.
I'm thinking skip the paint, just polish the titanium right up, should be pretty sweet looking frame.

He's pricing the tubing out for me, we'll see how the cost comes in, see if it's in the budget.
Anyone out there gone this route?

 

[sensor]

you might want to go with .065 tubing since thats the standard for bike frames/bars itll weigh less and i doubt youre gonna be jumping it when you done so itll hold up just fine :wink:

 

[Uncle Stretch]

Sometimes the things you draw and the way it comes out are not always the same. I have built a few , and a couple ended up in the scrap pile. I would think for your first try at frame building ,you would use cheaper materials , like regular steel tubing. I have a buddy that is also a machinist and he can turn out some really fantastic stuff on a lathe ...he isn't worth a darn at frame building...Good luck

 

[viking]

Sounds like you already have some good advice and ideals from some of the more seasoned builders but I'd like to add my two cents if I could. Before making a jig, I would get all the components together,( seat, handle bars, wheels & tires, ect. ) then build your jig putting these parts in the location you want them to be . I think you'll have better luck building a frame that will fit you. Have fun and when you're done you'll have a one of a kind bike built to fit you.

 

[sensor]

looks like a cross between a fluid and classic fbr......
what id do is find some people who have both or either of those frames and ask very politely to have them measure everything you want dimensions on.....
if you search firebikes on here theres quite few members who own them and most are willing to go out of there way to help.
good luck

 

[sensor]

OR.....
you can get a picture of one and graph it out and get the full scale dimensions that way
you can also send me some cash and a sketch and i can build it for you as well :wink:

 

[firebikes]

due t o the fact we handbuild our products we can modify any frame or build from scratch.. thanks for you support guys...sam