I am a frame builder AMA

Why do some frames/bikes have really specific part degree head and seat tube angles?

I've noticed it before but this Erikson in the classifieds just reminded me about it. 71.7 hta and 72.7 sta. Why wouldn't you just make it 72 and 73?

I kinda start with the hta and sta when I'm drawing up my design for a frame, is it just a case of other measurements have taken priority for that builder and that's where the angles have ended up?

product differentiation bullshit or people designing stuff who don't know the tolerances which can be held during fabrication. (Blame the engineers)

I don't know of any framebuilders who are measuring the angles with any sort of accuracy to be able to hit those numbers. Your standard anglefinder reads to either 0.1 or 0.05 but in reality are only accurate to +-0.2 degrees.

Is it weird to spec a 1" head tube with oversized tubing?

Not really, if you're going by the standard 'oversize' of 31.8dt 28.6tt

Thanks :)

I have a set of heat sinks/purges that were bought for a project that never happened that i'm looking to sell. I figured someone in here might be interested before i list them elsewhere. I bought them after reading decent reviews in this thread, here is the eBay listing:

https://www.ebay.co.uk/itm/223954411490?hash=item3424b91fe2:g:0EYAAOSw8kFgMV-g

I have a 27.2 seatpost, BSA 68/73 mm BB, and head tube 34 mm. They are all unused and packaged. I paid £500 for them and would like to recoup as much as possible for them but hey, make me an offer. I can take some pictures tomorrow if anyone is interested.

Id maybe take the bb/seat tube ones if you dont mind splitting, pending price etc. Are they purge-able?

Yeah I would be happy with that. PM’d

Anyone know Trevor Watson of Autumn Frameworks?

Do any of you frame-building folks have a fork crown knocking around in your workshop that I could buy and give to Winston?

For 1" steerer, with wide tyre clearance.. like this from Ceeway (unfortunately sold out for now). Doesn't have to be this exact one, just something similar:

1 Attachment

I think I have a 1” version of the one Surly use on the steamroller fork, not quite as much clearance as that. Probably 50mm.

Any use?

Thanks @M_V : )
I think that might be just a tad too narrow but will check with Winston tomorrow and get back to you.

No worries.

I’m at work the now, will try and remember to check my box when I get home incase I have anything else.

Amazing, thanks man : )

Nothing else in the box I’m afraid, must have used the I was thinking I mighta had.

This Surly style one is just the 50mm clearance version.

1 Attachment

Ah thanks @M_V , pretty sure that's the one Winston already has... probably not wide enough.
Much appreciated though : )

I want to put a rigid fork on this mini guy - because of the weirdo Q suspension doodad the A-C is 390 ish - steerer is similar.

Anyone got a view on what the cost of making me a custom fork would be ? - don't want refined - want raw / hack / franken thing so I can add a front basket / rack. Would need some kind of bridge lower than the crown to take mudguard and rim brake + eyelets for rack - maybe a disk tab to future proof.

1 Attachment

I'm not a framebuilder (yet?), and just out of curiosity, I wanted to ask a framebuilder how modern steel integrated head tubes work. Like, where does the bearing rest on? In the image I attached you see the picture for a tapered headtube, from the columbus tubing website. Is there a ledge inside the headtube where the headtube rests on? Otherwise, I imagine that the hearing would just fall through... The walls are just straight, there is no stopper or some kind of lip...
And how would that even work for different size frames?
I guess that there is nothing special inside of the tube and that it has to be added when you finish putting your frame together.

1 Attachment

You get some rings to braze in at the ends of the head tube :)

Or you can get steel headtubes with bearing seats already machined. Like this one:

Paragon Machine Works are even kind enough to give you the drawings

https://www.schonstudio.com/

never seen a dropout like so!

1 Attachment

Thanks guys. I knew about the pre machined headtubes but was wondering about the non pre-machined tubed.

But as @PhilDAS pointed out, i just found this picture on Ken Evan's instagram. Now I can clearly see the brazed in rings.

Really contemplating on trying to build my own frame. I'm inspired by Phil's thread

1 Attachment

Another one, same rings

This is the Columbus Cento frame.

1 Attachment

Oh cool @disq

I'm drooling all over these handbuilt steel frames 🤤