My first scratch build - bobber style

#1
alright, so I've been wanting another bike for some time now (since I got my rupp going pretty much). problem is ALWAYS the money, since I don't have a job I've got the time but no funds to support the ideas. Well looking through everyone's projects I decided I don't care how long it takes I wanna give it a shot. So I drew up another frame style that included bits and pieces from my other 10 million bike drawings. out of all of them this is not only the neatest sketch but is also the first one I'm also planning on following through with.

I've always loved the look of bobbers- stripped of just about anything that doesn't require it to run and drive, rigid and low. I'm 6'1 so I needed something kinda longer than I originally wanted to go with in other drawings. according to this drawing I plan on using a briggs 5hp flathead, headlight and taillight which will probably be run off a battery of some sort. 20" bicycle wheels, I'll buy brand new bearings and some whitewalls for them later on. and of course a peanut tank that I might pick up from imperial bicycles. unless I find one bigger and cheaper on eBay. anyway here's the drawing.


we've had some thin plywood laying in the garage since we moved in, so I took a sheet and wrapped it in some gift package stuffing paper stuff.. mom told me what it was called but i don't remember. what I DO know is that i can reuse the plywood for future drawings and I can keep this drawing rolled up in case I wanted to duplicate it- and that's all that really matters. In this picture the lighting is a bit too much towards the center but you kinda get the idea.


And here is what I have to fill in the blanks as of right now. I used a tubing cutter and a little bit of a hacksaw to cut up an ignored mountain bike today, the frame was circular so it worked out. That engine block is done for, it's there for mockup but I'll need a new engine. the rear fender is getting chopped up like you see in the previous picture. the red wheel is also done for, might have another one laying around though. The handlebars might get swapped with something lower if it's comfortable but for now the mild ape hangers will do. they aren't lined up with the neck area because I plan on getting something like this Chopper fork Chrome Street Lowrider for it, though those ones are pricy and probably too long. And yes I know I need a better camera. :doah:


Don't know exactly what I'm going to do as far as the drive system yet, I was thinking maybe a TAV unit just directly chained to the wheel, or should I do a jackshaft? :shrug: Then there's also should I put a bigger sprocket on or use the original freewheel? :shrug: those questions are still in the works and maybe you guys could help me out with that.

I'm still a newbie at welding but I have done a little and I've got a guy that'll teach me along the way, the only one I have access to is MIG so I dunno how you guys feel about them but any tips are always appreciated.

so that's where I'm at. I'm extremely excited to get started on another bike project, I'll try and keep things flowing in a timely order but money can be hard to come by sometimes so I won't guarantee anything, but as of right now this thing is going to be built, even if I don't finish till 5 years down the road :doah:
 
Last edited:
#3
good plan. mig welder is fine. id probrobly just use a clutch and jackshaft. tav sticks out too far and really isnt nessesary for street and flat land riding imo. youll probrobly need somthing stronger and bigger than the bmx freewheel. Its easy enough to weld a sprocket on the hub if the center hole is genrally the same size. I build my first bike completely out of bicycle frame and it looks great. If you want it to look more like a motorcycle and less like a bicycle you should do a double down tube and a bigger diameter top tube
 
#4
good plan. mig welder is fine. id probrobly just use a clutch and jackshaft. tav sticks out too far and really isnt nessesary for street and flat land riding imo. youll probrobly need somthing stronger and bigger than the bmx freewheel. Its easy enough to weld a sprocket on the hub if the center hole is genrally the same size. I build my first bike completely out of bicycle frame and it looks great. If you want it to look more like a motorcycle and less like a bicycle you should do a double down tube and a bigger diameter top tube
cool, tavs are kinda expensive anyway. I believe I've seen jackshaft kits before.. I think.. I'd feel more comfortable using a kit than fabricating one myself. I was very skeptical about using the freewheel, that had a high chance of being replaced at some point anyway, I was just clueless as to how people were doing it. but I'll look into it. by double down do you mean like the two bottom horizontal bars curve up and meet at the center bar? (forgive me I don't know all the terms) cause thats what I was planning on doing, I know it's hard to tell from my layout but the curve beneath the bottom front bar is actually going to be like that. maybe I should cut more off the center bar and make room for larger curves? And I may consider thickening the top tube later on depending on what I end up coming up with, but it's not on the top priority list.

thanks for the suggestions, I really am excited about this build. :freakout:
 
Last edited:
#5
yup two tubes all the way from the back wheel under the engine and up to the steering head. you can look on motorized bicycle forums for ideas on how to put a sprocket on the wheel they deal with that all the time :smile:
 
#6
cool thanks jeep :thumbsup:

getting a little ahead of the game here but... I think I got myself a paint scheme.


I love making these graphic schemes the only problem is that theres too many good looking combinations. I think I'm set on the colors, I'm waffling between the tires though, either both whitewall, both blackwall, or rear whitewall... I'll make up my mind later.

EDIT: updated picture with shading.
 
Last edited:

TomH

New Member
#7
Your drawing looks awful long IMO. Here is another idea, single down tube. Front end needs more rake and I wouldn't have squared in front or back of the motor but kept the arcs. Oh well you get the drift, smooth this one out and it would look a lot better.

 
#9
Tom, thanks for the input. The bike in the drawing is about a foot longer (estimating here) than in the actual layout. If you look closely, because my camera takes crap pictures, you can see on the layout with the parts that it's a little smaller and there's A LOT less blank space between the engine and the frame in any direction. And for being tall I think the length of the bike as it is in the layout will work out fine. I've never been a huge fan of the curvy choppers, don't ask me why, don't get me wrong I've yet to see a build on here that I didn't think was awesome. I just wouldn't build that style myself, to each his own I guess. :shrug:

and Tank as of right now I'm short on just about everything. I owe myself like 40 bucks after I bought a billet rod the other night so I have 0 money to spend on anything. I have another front wheel I need to grab from my uncles house because that red one is bent terribly. other than that I need, tubing, headlight, tailight, motorized bike sprocket and adapter (havent decided what size yet, maybe a 44t?), chain, peanut tank, chopper forks, clutch, jackshaft kit, throttle grips, other random odds and ends I'm not thinking of at the moment.... there's a WHOLE shopping list I've got to fullfill. Thats why I say this could take awhile, but it's something I've always wanted to do even before I was into minibikes so It'll get done.... eventually. :doah:
 
#10
haven't forgot about this project, just been too busy with everything else. believe me the desire is more than there but I'm not quite ready to truly begin this yet. HOWEVER that hasn't stopped me from day dreaming and rethinking the entire thing.

turns out drawing bike frames is a really good pass time, after a few different variations I've ended up with this.



I pretty much trashed the old frame idea because it was based on what was easiest to accomplish rather than the overall look of the bike. the newer style is a lot more round and compact, much less empty space around the motor. it's designed so I can sit nice and low to the ground, run a jack-shaft, and make use of one of those fancy springer front ends. I like the look of both the ape hangers and the low bobber style handlebars but what I actually use depends on whats more comfortable, picturing it in my head it'll probably be the lower cut bobber style. And of course I'd like to go with my favorite engine, the all famous 5hp flatty with a billet rod shaved eyebrows, and a tec carb. in the picture it shows a velocity stack for an intake but who knows what I'll actually use (maybe another meat grinder :shifty:).

so I've got a pretty good new-and-improved brainstorm going on now I think.

as for the way the frame is put together, the front-bottom bars come up in an upside down V shape to meat up with the middle tube (the arc shaped one) and the the back end of the arc tube will be connected to another horizontal tube that connects the two half's of the bottom tubes.... :shrug:
..it's kinda hard to describe what I have in mind. so I'll put together a sort of 'explanation' drawing so it makes a little more sense. I'll also get to cleaning up the drawing a little bit later today.

what'chu all think so far? :shrug:
 
Last edited:
#12
thanks Clay, and I agree! :thumbsup:

I got the drawing cleaned up a little bit today, not gonna worry about making it pretty till later though.



and just for the hell of it and in the spirit of OldMiniBikes here's an older style I went all out on a few months ago with a few irritating mistakes. :hammer:


EDIT: if you don't see any pics it's because imageshack is being kinda glitchy lately.. :doah:
 
Last edited:
#13
Nice you have some creative idea's

If you are open to some crit and advice let me know, have some nice ideas and thechniques on scratch building a frame

keep going
 
#14
Nice you have some creative idea's

If you are open to some crit and advice let me know, have some nice ideas and thechniques on scratch building a frame

keep going
I'm always open to criticism. Speaking of criticism, what do you think of a belt style 'manual' clutch. Basically a direct pulley drive, engine to jackshaft with a stick lever controlled tensioner. In one position the belt will be loose and slip, and in the other it will be tight and drive the bike.

I know it seems like one of those "why the hell would you do that when you can just do _______ instead :eek:ut:" I just like to do things differently, and I like the idea of a suicide shifter. :drool: anyone ever do something like that before? If I'm in over my head I guess I'll just use a centrifugal clutch and leave it be, but I'd like to give the manual clutch a try first.

And also I'm more than ready to start this project but I just can't until I get my rupp back together, just no room right now. :doah:

Hopefully soon :freakout:
 
#17
Nice updated Pics:thumbsup:

I just wanted to show how I bring and engineering component to a scratch build, this gives you better feel for what you want and still lets the artistic side come out.

I normally get the misses to help out but I'm sure you can find a buddy.
First visualise yourself sitting on the bike, then find something that same hight as the seat you want, I like books cause its easy to adjust the hight to where you want it. All I had at work was a paint can and a chair, but you get the idea.

Then sit how you want to on the bike, and hold a broom handle where you want the bars to be. Then Measure the key dimensions
Hight of seat
Hight and distance of foot pegs
Hight and distance of handle bars etc



Then just like you did with block paper let one block equal say 4 inches ± 100mm then draw in a stick man of yourself to those dimensions you took. My butt was about 9 inchs off the ground on the paint can so 3 block high. The bars are about 24 inches so 8 blocks up etc. I even measured my clone, so I could draw it in in scale.



This allows you to walk the fine line between art and engineering - You have some awesome ideas and tallent, keep pushing the boundrys.
Love the idea for a suicide clutch:thumbsup:

 
#18
I used a simple lever clutch like you are talking about years ago on a mini bike, only because I couldn't afford a new clutch. Everyone loved to ride it. When you make it just make it break over center and it will stay engaged or disengaged. For your build I think it would be the cats butt.

Jimmy
 
#20
A lot of old motorcycles from the turn of the century,1900...Not 2000...Like Harly/Davidson,Henderson and such all had belt drive in one form or another...And used a belt clutch like what Your doing...Check out some of the motorized bicycle sites,they have a section that deals with D.I.Y. powered bikes...One has board track bikes replica type builds...Lots of good info that could cross over to Minibike use....Scootercat....
 
Top