CP: The Topcross (Low trail CX + touring)

31.8 isn't that big. Also, it's a large frame, so might benefit from some extra stiffness.

Unless @Hulsroy is just using any old tubing that's laying around ;-)

On the top tube tho?

Downtube, headtube, BB junction definitely but top tube and seat tube less so (AFAIK).

Oooff. I trust you are okay?

Yes thank you. It happened a while back. No harm to me.

@edscoble @BareNecessities

My road bike is 31.8 top tube and 35 mm down tube Columbus Zona mtb tubes. And that is lovely for my size and riding style #julemandsfysik

Regarding using a 31.8 top tube on a bike that already has a 31.8 downtube. It probably isn't necessary, but I want to use the leftover top tube to make the down tube gusset (that will make a nice transition from gusset to DT) and I think the bigger top tube will also give shouldering a bit more comfort. Any ways, frame is broken, so I might as well experiment.

I am thinking about ovalising the toptube. I can not find any methods using google, so I must be using the wrong words. I thought I once saw a guy doing it using some planks of wood and a vise.

Anyways, my current idea is to CNC some hardwood and the use a large garage press to form the tube.

@mdcc_tester can you tell me if this will work?

For the seatstay/top tube junction I am hoping it will look a bit like this:

@coldharbour is your man for that, he loves reshaping tubes.

You are right. Thank you.
Maybe Matt has an idea of a smarter way.

I will just test it to see what happens...

You and Matt could do a rat bike collaboration.

Hulsroy X Talbot

Your plan is legit, although from personal experience I would suggest bottle Jacks, at least two, as you'll have a mare evenly distributing the load (or even getting adequate force / fitting into vice) using a vice.

Thanks Matt. I will give it a go.

Got around to machine a shaping die today.
I changed the design of the die so it is only half a tube shaped at a time. I clamped the round part of the tube with a F clamp and put the die in the wise. I worked my way from the round center to the oval end slowly.
I will do the other end on Monday. Got kicked out of the workshop by the guard 7pm. Oh well...

the bend is a bit sharp. Next time I will try with an internal die in steel, turned on the 4 axis cnc. Edit: I think it is called an oval mandrel..

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Replaced the top tube finally. Need to file one more fillet and then braze gusset and then some more filing. Decals turned out nice, so now I just need to decide on color.

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Nice work!

TA

loving the decals-how about putting them on over the bare steel and then just clear coating the frame to seal it?

^ this aaaand when the frame starts to patina under the clearcoat it'll look even cooler imo

I hear you, but it is not durable in the long run with clear spray and this is my Cx frame. Powder coating is necessary

Took a while to shake the illusion that the brake bridge was a big kink in the seatstay!

;-)

It is an S bend seat stay. They are a fucker if you hand mitre.

Getting there. Luckily the workshop has been quiet this week. Hopefully ready for paint tomorrow.

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Are you going to move the Gundersen decal up a bit this time?

dat gussett .mov

Pls share a link to the international decal codex? I will obey if there is proof you are right

Absolutely amazing work you've got here, not sure why didn't I notice this thread so far.