jtfix

Has anyone seen bridges like this before?

I picked this 49cm frame up a wile ago, before the new colour it was metalic cherry red with "Eddy Merckx" and "De Mayo" details on it. Although i wish it were, I'm positive it's not merckx. I don't think they ever made lugless track frames.
I'm pretty sure It's Columbus tubing from the dropouts and the lugs on the forks.
The seat stay bridge is very uncommon, flat and no attachment hole for a brake.
Has anyone seen bridges like this before?

gargiulo.mike

i've seen it on yamaguchi's and other choice frames.... nothing too special.

deathhare

Nope

jtfix

I did wonder if it could be yamaguchi but the dropouts are a very different style.

deathhare

Got a pic of the whole frame? Maybe someone knows what it is. You'd be surprised.

nayr497

I hope you didn't join just to start this thread. If you did, deathhare...you just ruined his virginal membership card...one thread up, one thread shot down...

deathhare

What? I suggested he post a pic so maybe someone can ID the frame.

jtfix

Good idea!

deathhare

wow, tiny frame. what size is it?

Wotan

...

jtfix

49! Yep very small, not a lot of toe clearance! If any! I wanted some thing small to play about on. I work on something bigger.

jtfix

"If you dismount a bike and straddle the top tube, and someone bumps into the bike from behind, the horn of the seat can poke you in the lower back, and cause incredible spinal-pain, if not scoliosis."

How do you recomend mounting a bike?

Apparently in Italy if you don't swing your leg over the bars and choose to go over the seat old ladys spit olive pipps at you!

apotnolid

those are zeus pista dropouts.

that seatstay bridge is not uncommon; builders have the luxury of using whatever scrap plate/tubing they want for chainstay bridges, and seatstay bridges on track/fixed wheel frames. however, flat plate bridges like that have the potential to be stress risers if not brazed well. see the nice big fillets on either side of the yamaguchi bridge? sweet. see how on your frame the bridge is just kind of blobbed on there? a little iffy. from that detail, and some other details about your frame, i'm thinking lower budget production track frame from the mid 80s. i'm also thinking replacement fork due to the long shen crown, but that's a hunch.

Suttree

I want to hear more about how the bridge creates a stress riser. This is a topic I've been learning more about lately. A local shop was showing me how different frames fail based on how lugs concentrate stress.

Long shen lugs are just fine though. I think they show up on all kinds of bikes, including Makino.

c0urt

i have seen double bridges like that on a makino

apotnolid

the comment wasn't meant as a negative to long shen lugs, just that i think the fork looks a little extemporaneous to me compared to the frame. i.e. frame came before fork.

i wrote this big long thing on stress risers, but it really wasn't necessary. if you need more info google will be your friend.

bicycles for the most part are made out of tubing, not plate. since this tubing is typically very thin walled, any points where the tubing is joined to other metal parts need to be very well reinforced so as to lead to even stress distribution. though this isn't really relevant, a good analogue is an auto window. if you slap it as hard as you can with the flat of your hand, you probably won't brake it. the surface area of your hand distributes the stresses upon impact. on the other hand, if you strike it with one of those little ballpeen hammers that has a diamond tip on it, it hardly takes any strength at all and the thing just shatters.

plate joined to tubing has more hazardous potential for inducing stress than properly mitered tube to tubing. that's why on that yamaguchi there are nice, fat fillets to help with even stress distribution between the bridge (plate) and stays (tubing).

extrapolate that to lugged frames.



if these were just put-up onto a frame as is, they would be stress riser city with all those straight, blunt edges. very early frame makers tried to use lugs like that (very common in early pipe-fitting work), but figured out that if you curve the lugs, and have them taper to a small point, the same stresses that ****ed their earlier frames are now much less likely to cause failures.

so, carving lugs with curls and nice tapered points actually serves a functional purpose, to a degree. neat, huh.

Igneous Faction

That is probably not a production frame. Who was building 49cm track frames on a "large" scale in the 80's or 90's? None of the bigger names...

I'm going to say that's a custom frame.

apotnolid

whoops, that should have read "custom" not "production." instead of editing i'll leave it in my original post for thread posterity.

operator

If you're going to have bridges like that, why bother having them at all?

c0urt

the hot sex