Black Bean [a burrito]

[onelesspedestrian]

I'm starting this build for a few reasons.... First, I had these two bikes laying around, that aren't anything I'd typically do anything with. When I pulled the fork and front fender off the girls bike to use on Hot Rod Girl the remains of the bike just kind of dropped down in a certain way... and I had this big ol' ten speed frame, not useful for anything else sitting around, so I lined that up infront, upside down:

Chop chop chop.....

Originally I was going to leave the girl's frame intact, but it's going to look way better if I cut it up some more to make the lines better. The other reason getting me going on this is that I got an Oxy/Acetelene torch for Christmas, so I'm excited to play with the new toy! I'd rather practice on scrap bikes and make a cool low bike while I'm at it rather than just practicing beads. I more or less remember what I'm doing from highschool anyways. I also want to see what this "burrito" business is all about, so I'm gonna slap this one together and find out. Since this is my first bike chop of this type I don't want to get TOO carried away with craftsmanship and such. I'm just going to have fun playing with fire, keep it real cheap and ratty, while trying out a few ideas.

Here's the other night, with the top tube mitered up and ready to weld. the front section off the girls frame is approximately where the bottom of the frame will sit (minimal ground clearance, and horizontal.

I've since welded this up, and begun work on curling the fork down to match the right way. Updates on that, and hopefully more, later.

 

[bikeriderx]

Great start! I got a new welder recently and I can't wait for the weather to warm up so I can get out into the garage!

 

[onelesspedestrian]

don't wait.... the heat from the welding will keep you warm :wink:

Well, most of you stays warm, I come in when my toes start to freeze.

 

[Pinche]

You know your really concentrating while welding when you don't even notice your on fire. lol. How many people can't say that's never happened to them? Maybe if you rock the fluxcore still. Hahaha. Looks good.

 

[onelesspedestrian]

I got a bit done today.

I got the middle tube of the frame put in, which is the old seat tube off the 10 speed frame. I had trouble getting the BB shell to weld to the down tube, I couldn't get it to pool and fuse together, I'm not sure if it's because it's a lot thicker, or if it's because the metal is different (cast?), so I hope it can be brazed. I am going to pick up some brazing rod and try.
After I got that tube in, I cut the bb off the ladies frame. I also took the seat tube off above the original ladies top tube lug, which was where it was bent. I trimmed the lug off that remaining stub, and then I will wield it back on, eliminating that bend. The downtube off the ladies frame is mitered up and ready to become the bottom frame member.
I didn't have my camera on me while working today, but here is the aftermath of today's work:

Here is a bar/seat mockup I am thinking of at the moment. I could also see this bike running a banana seat and HUGE apes, but this is what I have, so I'll try it.

Well it's looking promising so far. I'm pleased with the lines it has, considering it's just 2 scrap straight tube frames. I'm going to add the seatstays from the 10-speed into the rear end, lining up between the axle and the mid tube, kind of like a mixte frame. I was also playing with one of the 10-speed chainstays as a bar to frame in a 'tank' area at the front. I still have to decide if that has the visual appeal to want to put it on.

 

[stretch]

looks great! from a slighly experianced burrito-er, your on a good path. lets just hope its flat enough so you dont bottom out all the time.

 

[onelesspedestrian]

I figured you'd like this one....

Yeah, I will have to just ride it with that ground clearance and see. I do anticipate 'laying frame' every now and then. hopefully I can get in and out of driveways still. The bike has more trail in the front end than I would have liked, but I see a lot of these look like that. I don't know if that's because a lot of builders don't curl the fork down, or what, but I'll see how this goes, and the next bike will inevitably have better geometry as needed.

I'm glad you're looking at it and think it will bee good though!

 

[stretch]

if by trail you mean the tendancy for the front wheel wanting to turn to one side or the other cuz of the extreme rake, thats part of building a burrito. theres no escaping it. and your will have plenty of clearance if you chop off the excess tubing.

 

[onelesspedestrian]

Wow... sorry to anyone who's been waiting for an update on this one. Life's been funny lately. Between nearly dying in a blizzard, then crashing my Bronco II, I've barely even been on the site, let alone done any work in the garage and posted up about it. Anyways, the other night I had a good night of work out in the garage. here's where it sits now:

sits a bit shorter than most Burritos, but I limited myself to the material available from these 2 frames. even at that I am always a fan of keeping excess length out of the rear(from the seat, back)and in my mind, on a bike like this, no more length is needed in the front to keep your feet off the tire.

I like this shot. It does a good job of showing some of the lines I was after. I have always liked the mountain bikes that have a straight shot from the head tube to the back axle. The seat is just sitting there, it may have to be mounted a little higher/further back, but it will be set right against the fender. I will have to decide if I want to go all the way to proper leg extension once I get it up and running. seat slammed right down would still be rideable for me, just a bit cramped.

 

[SSG]

Looks great. I actually made mine too long. I need to move the seat forward a few inches or take a few inches out of the frame.

 

[stretch]

looks awesome! i think its a tad short, but thats just me.

 

[rgallen]

Cool, I like the lines. I just can't bend enough to ride one.

 

[onelesspedestrian]

this is my first foray into burritos. you guys that are big into these must have real storage nightmares. rgallen, it seems like I am just sitting in a chair, holding a pair of handlebars in a natural position when I sit on this. I may end up going to a banana seat if all else fails, otherwise I will just move the seat up and back a bit. I don't really want to go the banana route, since this is supposed to be just a rearranged pile of the junk sitting around my garage, and I'd also want giant apehangers to go with a banana seat, both of which need to be purchased. aside from gas and filler rod, this is still $0.00

 

[onelesspedestrian]

big bike in a little stand....

I cut the clamp off, and welded a section of 7/8" on at a right angle.

Right after the maiden voyage around the neighborhood... I think I'm going to do a bit more adjustment to the front end geometry. There is too much trail right now, which wouldn't be so bad, but at this angle the wheel flops, making the front end drop in corners, and I have to muscle it straight. I think I will mount the seat 'underslung' instead of how it looks here. what's the point of such a low bike with all that daylight between the seat and frame? it's madness!

 

[stretch]

but the front end flop is part of mastering the burrito! after a while its not bad at all. i built one with worse rake then yours. but thats just me. you could fix it by adding tubing to push the headtube forward, but it would change the sleek look.

 

[jOe]

This thing looks like it's going to be a sweet ride. I was thinking about your front end geometry issues though, maybe some math would help?

The great thing about the internet age though, is that there are online calculators to do the math for you! This one looks like it might be perfect for burrito engineering, it uses the structure of your current bike to give you options for what to do with the front end angles and measurements.-

http://www.wisil.recumbents.com/wisil/trail.asp?calculate2=yes#Actual Trail Calculator

this one uses your current angles and measurements to tell you what your trail is-

http://yojimg.net/bike/web_tools/trailcalc.php

It looks like if you've got a 50 degree head angle and big 27" wheels, (it's a best guess, I've never measured a burrito) you're going to need something on the order of 14" of fork offset to get in the realm of what is considered "optimal high speed trail". Not that that's what a burrito is about, but, if you're looking to improve the handling, you could try making the head angle a little steeper, or raking your fork waaay out. (a truss fork might look really ........)

 

[stretch]

a burrito always has flaws, and the art is riding it regardless.

 

[Rustinkerer]

Sweet! Much love for the junk-built primeval burrito! -Adam

 

[onelesspedestrian]

yeah I understand the math, actually (thanks for the link though, jOe that looks like a good calculator). I even designed automotive suspension geometry while I was in college, on a Formula SAE car. In fact I am kind of kicking myself for not doing more design work before starting up the torch. However, in the spirit of this build, I sort of winged it, and seeing what others have done with burritos, I thought I was in the ballpark. Not to knock anyone else's work, but now I realize that this is one of those things sometimes overruled by looks rather than performance. I'm sure a lot of the similar bikes I have seen ride just like mine, and that's fine, but being that this is as much of an experiment as anything, I am going to tweak it further.

I think what I will do is to start by curling the fork as far as I can while still getting the wheel in it, then altering the head angle until the front end height comes back to where it was (the bottom of my frame needs to sit parallel with the ground). Trail as it sits is about 9", and I think I can cut that figure in half.

it also just occurs to me, that I should measure up this bike for trail, since it rides really nice, just VERY cramped.

 

[deorman]

More leading edge will definitely reduce flop, but it looks like you'll need a longer fork to go very far. :|