baxtefer

i know this bike belongs to someone here - It's the jonny with the perforated top tube.
but what bars are these?
that's some serious drop.

onetwentyeight 

guessing: soma bonzo bars?

Slodo

So awesome! Gotta be a custom job; I've never seen anything like that.

DonPenguino

At that point I'd just go for the bullhorns off the front fork. I can't remember the guy who had them, but I think it was a Russian olympian.

MLPROJECT

rebent b123s? metal fab dudes can do whatever they want if they know their tools

endform

Can we start a betting pool for how many miles it's gonna be before the frame cracks at those holes?

chuck_norris

I agree that metal guys can are capable of crazy ****, but that's no nitto bar. It doesent have the cuff in the middle. I think that the guy that bent that just used a mandrel pipe bender. Used frequently for bending the exhaust pipes on cars. I'd imagine that those are pretty flexy considering the elasticity needed for that kind of bend. I could be wrong though.

MLPROJECT

i mean, that's johnny in the pic... where's he at to answer this one?

freebird

Jonny told me that they are actually old-timey track bars that he's been saving for just such a bike. Freaky-deaky.

chuck_norris

Cracks have a lot of trouble propogating from round cutouts. That's basic mechanics of materials talking.... basically why windows on planes don't have corners. I don't know the steel used, but I'm pretty sure there isn't much of an issue.

At least with steel you'd see the crack grow before failure. Had it been made from aluminum...

mattface 

this should end the speculation.
That's Jasonsan's bike
https://www.bikeforums.net/singlespeed-fixed-gear/174769-baby-blue-cotton-tape-handlebar-pics-inside.html

endform

But those cutouts are very large compared to the diameter of the tube, does that affect anything?

chuck_norris

the radius of the cutout is inversely proportional to the likelyhood of crack initiation. In simpler terms: A bigger round cutout is less likely to have a crack start around it.

In fact the reason that most frames have that circular hole at the bottom of the seam where the seat tube cluster binds the seat post, is exactly this principle.

chuck_norris

I may have misread you're question. I think you're wondering about the structural integrity in general. Such as a buckling of the tube at that hole?

From what I know about frames, the downtube undergoes the most stress in ordinary riding conditions (we aren't talking about what will happen to the frame in a wreck). Obviously the less material present, the larger the cutout, the more stress will concentrate on the rest of the material. The fact that the holes are drilled dorsally is definitely good thinking from a srtuctural standpoint. And from an innovative standpoint, because from my recollection Jsonsasn has the largest hole drilled the same diameter as his lock, that just plain neat.

spud

that headtube is like 5x the size of #28

Nachoman

Not my style. I like a more relaxed position. I get enough stress at work.

concernicus

jonny told me he got em of ebay. they were rusted so he cleaned em up and painted em. now they look snazzy.

biketolive

Hi
As I can tell you know some stuff about simple mechanics of materials but as I am sure you also know that just because you can't see any cracks forming doesn't mean that there is not yeilding occuring. In fact in most materials (exculding hardened materials which follow simple plastic deformation curve) will yeild to a great extent before catastrophic failure (complete failure meaning Er > Eu). If there is such stated holes there will be less deformation before ultimate failure. That being said if failure is do to a positive moment in the x direction there will be little differnce because of the small reduction in the I value due to the holes being on the nuetral axis. I hope that clear's up some of the points stated by some of the other members. Jay

biketolive

sorry to get off topic but Chuck I agree with you, but could you tell me why they put the holes in that specific spot. Klein also claims that it reduces stress which I can't see why because if it is in tension/compression there is a reduction in cross sectional area which increases stress. thanks jay

jasonsan

I got those bars from Ebay, that guy in Australia who often has vintage track stuff.Jonny brazed a new S/S center section on 'em, and capped the ends for me as well. They are not very functional...I think they are for a little kid with ape arms. Narrow and deep.......but I was going for style.

As far as the holes in the top tube go, I was inspired by the strawberry integrated seatpost clamp....... this .They aren't just open holes.There are s/s tube inserts thru my toptube. I originally asked him to put them in the downtube, but he said he wouldn't be comfortable with that. Will it hold up? Probably, but you never know unless you try, right? Again, this was done simply cuz I thought it'd look cool, not for any other reason.The u-lock thing was a nice coincidence.
Interesting that the topic of durability came up here, and not at the show, or on the framebuilder forum ( where we were expecting some debate). You guys are on point!

lunacycle

I think the s/s sleeves will brace the walls of the tube at the holes. The top tube is primarily in compression, with some torsional forces. I would expect that the tube would fail in buckling at mid-length prior to the onset of yielding near the steer tube. I don't know what role fatigue will play in all this. Anyway, just my 2 cents.

Sinfield

I'd imagine that with the round inserts in there, you would be golden. I notched the framerails on my old GTI and welded a piece of pipe in the cutout so that I could slam the car and not rub the axels and I never had any issues. Sort of the same theory, round (or half round) cutout in what is essentially a hollow tube (toptube/ framerail), braced with welded pipe. I'd guess that there was a lot more stress on the car than the top tube of a bike.

baxtefer

yeah it sould be fine with the SS inserts

it kinda reminds me of that bike with the hollowed out chainstays. Was that a 3Rensho, or a Nagasawa?

edit/ 3Rensho

lunacycle

I hope those chainstays have weep holes along the bottom. Yikes!

dynaryder

Those look kinda like what they used to run on vintage racing motorcycles.

Which basically were just bicycles with engines.