ClarkinHawaii

Hey guys, looking at maybe buying a custom Ti frame with long headtube to support my high handlebars.

We're talking about a 20cm headtube on a 52cm effective top tube frame, sloping top tube. Got a face only a mother could love.

I'm hoping it looks better dressed than it does naked.

Surely I'm not the first old fart that needs a frame like this. If anybody has some dressed photos of similar, I sure would like to see. Thanks.

stanridgespeed 

not quite as tall however, 170mm tall HT with slight sloping geometry. 53cm ST 56cm TT. Built for a client with poor flexibilty, very short legs and long torso.

ClarkinHawaii

Thanks for posting--I was hoping somebody might have a setup that was more radical-looking. My handlebars are 4" higher than my seat, so with only 5cm of spacers, it makes for a strange look!

unterhausen

ClarkinHawaii

Now this one brings up an interesting point--your sketch shows the headtube the way I would like it. However, the designer i'm talking with says that "The head tube can't extend more than about
> > > > > > 3cm beyond the top of the top tube, for
> > > > > > structural reasons."

I asked "what structural reasons?"

He replied: "A long head tube extension above the top tube puts
> > > > a lot more stress on the top tube / head tube junction
> > > > (since the forces can't be dissipated in the steer tube
> > > > as easily)."

I asked on here and people seem to agree with him. What do you think?

I mean, is your sketch an actual, viable frame, or did you just throw one together in a cad program to show me what such an animal would look like?

mudboy

About 1.5" of "extension"

unterhausen

My advise to anyone is that I wouldn't ask a builder to build something they don't want to build. I haven't really thought through the structural issues. Having said that, all the action is at the bottom of the head tube, and I really wouldn't have much concern about doing this structurally. I would think about beefing up the head tube with this design. I build in steel, and there are some really beefy and strong head tubes available.

I just drew the frame you asked for in BikeCad. I was curious what it would look like. A lot of people at NAHBS asked me about frames like this. I would probably build it, but I'd want to see a picture of the person on a bike with this position before I did. An upright position like this reduces your power potential considerably. It also makes it so you can't go to a much lower position should you realize that you want to do so. Although this design does have 50mm or so lower before major mods start.

ClarkinHawaii

Great, Thanks, Guys.

tomn

Hi Clark,

If you wait until next week I will post some pictures of my new touring bike. It has a long headtube to start with. because it is a 52cm seat tube ctc and 26" wheels. Then I added a headtube extension because I have my handlebar height about 3cm above my saddle height. I made a stem that isn't sloping so the steer tube is very very long. I made it to fit, not to look at, but i think that when it is built up it will look good. It is at Spectrum powder coating now, but will be shipped back to me tomorrow. I am out of town right now so I can't tell you the length of the head tube.

Tom

ClarkinHawaii

I'll be looking forward to seeing it!

zzyzx_xyzzy

Salsa Fargo?


as for the structural deal, the bending stresses on the steertube are concentrated at the bottom but those on the frame are significant on both the dt/ht and tt/ht junctions. you almost never see a rippled downtube where the toptube isn't also damaged. additionally the steertube is often made of thicker stuff than the headtube. On most of the frames I see with a lot of HT extension those headtubes are made from 1.5mm thick steel or the extension is part of the thick steel lug.

unterhausen

buckling and bending are related but distinct phenomenon. Once a tube wall buckles, all bets are off.

fietsbob

For tall riders I've seen in Dutch Opa bikes, a ski tip like bend , to bring the Top tube up to the top of the steerer tube , at the Front.

but have a lower center portion of the top tube for straddling the bike at stoplights, than a straight sloping tube would allow.

of course in Titanium, adding wall thickness is always possible , that makes the same tube stronger , Its being done now, to add metal to Machine out for Integral headsets, and then given an Hourglass like OD reduction in the middle .

Shimagnolo

I guess no one told Lennard: https://www.facebook.com/photo.php?pi...id=61846853456

Better order a frame from him before he finds out.

zzyzx_xyzzy

1.5mm thick steel, again

ClarkinHawaii

OK, I see a Zinn Stelvio--no Lennards mentioned--is he Zinn's designer or what?

Shimagnolo

Lennard Zinn is one (very tall) man.
He can provide a custom frame in steel, titanium, aluminum, or magnesium.
This is his website, but for some reason it is messed up today: https://www.zinncycles.com/
He is located in Boulder, CO.

ClarkinHawaii

Thanks

Allen

tomn

Hi Clark,

Here are the pictures I promised:

https://www.flickriver.com/photos/cli...7624505281671/

Tom

unterhausen

Tom, how does that steerer lock work, is it threaded?

ClarkinHawaii

Thanks--I am also interested in the mysterious steerer lock . . . ?

tomn

I spend way too much time solving problems I don't really have. This is the part that is threaded into the head tube boss:

https://www1.mscdirect.com/CGI/NNSRIT...ber=1173Pmode=

It plunges into a hole in the steer tube when rotated which locks the front wheel in place. I thought it would be handy when loading panniers, and other times that I cursed wheel flop.

Tom

tomn

I guess I should let you know that ran a failure test on the plunger. I put one in and torqued on the handlebars. I applied a lot of pressure. The plunger bent to the point that it would not retract. I put a second one in and am hoping that it will take normal use. But I am carrying this:

https://www1.mscdirect.com/CGI/NNSRIT...ber=1177Pmode=

as a backup.

Tom

unterhausen

wheel flop has always been a very big annoyance, particularly when you want to be using both hands for something else. The flickstand was nice for that back when all tubes were the same size