mikeread

I have shortened it 10mm at the top and 5mm at the bottom. I didn't want to take any more off in case I struggle with the seat tube mitres and they end up a bit lower than planned - this was the trickiest bit on my first build. My mitreing should be better this time

What causes the seat tube to bulge Doug? My biggest tip is a No7 multi port tip, I was going to use this one for this job, just heat the sleeve and try and get the silver to the bottom with the minimum of heat and no direct heat on the ST.

Will go for it tomorrow if I get time.

Doug Fattic 

The reason the seat tube will bulge at the lug shoreline is because it is not at the same temperature as the sleeve and expands more quickly. If it got hot enough it wouldn't return to its former shape. This can easily happen when spotting a frame together. It is easy to get the thin top of the seat tube red before the sleeve/lug is up to brazing temperature. The solution is to use a bigger flame held back further so it is heating a broader area and bringing them both up to the same temperature at the same time more slowly. A flame held too close to an exposed part of the seat tube can expand it faster than a heavier sleeve. Be careful with your flame pattern. It is common for those on the earlier part of the learning curve to be a bit sloppy with their flame pattern. The don't keep the point of the flame a consistent distance from the tube and perhaps get too close and hold it there too long on just the seat tube and suddenly it is red and bulging.

mikeread

Thanks Doug that is useful to know

unterhausen

If you are using acetylene, make sure you don't over-draw your tank. If you are using propane, carry on

mikeread

On all my bikes the rear brake cable is run under the TT on the left. In the UK we generally have the rear brake on the left which means that the cable always rubs the paint off the head tube. I notice that in the US you have the rear brake on the right, which means the cable loops around the head tube into the cable stop on the left of the top tube. Does this mean you do not get cable rub on the head tube?

So I am now thinking, is it practical to fit the front brake cable stop under the TT on the right side and the rear one on the left, both at a slight angle so the cable crosses right to left under the TT. Would this help the cable clear the head tube and give a smoother cable run? Edit - I am using calipers

ST sleeve went on no problem at all. I even got the shore lines nice and neat - mostly, there is one bit needs a bit of cleaning up but I will leave that until after all brazing is done.

Thanks

Mike

Andrew R Stewart 

Mike- Cable routing is an aspect that I have given a lot of thought, mostly motivated by solving routing problems on factory made bikes, during servicings at the shop. I also run my rear brake on the left side lever because my right hand is better at modulating lever pull, the front brake is the one that will either kill or save me dependent on how I use it. I strongly like casing loops that are as gracefully curved around the corners of a bike. Especially at the head tube where a cable/casing in a really short length/tight curve can add steering forces. Being a short guy the lever to frame distance is less then most. On my calipered road bikes I have the forward cable stop placed on the right side of the TT about four fingers width from the HT. It is placed around the TT at about the 4 or 5 o'clock point. The rearward stop is on the TT's left side to allow the casing loop to the caliper to be minimally curved, again about 4 fingers from the ST. The cable runs under the TT (and on some frames I place my HPX pump under the TT too, if you do this take care with stop placement and pump location) and through a plastic liner sleeve. On the Canti bikes the front stop is the same and the rear one gets placed on the right side and how far from the ST is determined by the casing loop to the stay stop (or brake arm if a linear one).

Here's a shot of my S&S bike with the cable crossing under the TT as example. Note that the stops are further from the ST or HT then usual. See how smooth and few bends the casing loops have? I do get some paint rub off in a few spots. This has never been an issue for me, sort of like are getting winkled skin where we stress it. But it would be easy to add casing guide loops right on the side of the HT or lug edge to contain the casing's rub to a, perhaps, SS loop made from a spoke. There are lower head lugs with this feature out there but I'd make my own loops. Andy (who has sworn at bike designers many times, may they be required to work on the bikes they design over and over )

mikeread

Thanks Andy, that is exactly what I mean. Have you used special stops, they look like they are on stalks?

I have some nice cast cable stops, a bit of careful mitering and they should be good to go without any further mods.

TiHabanero

'"If you are using acetylene, make sure you don't over-draw your tank. If you are using propane,"

I did not know anything about this condition. Thanks for bringing it up. Some things are good to know.

Andrew R Stewart 

On this frame with the couplers I wanted a little bit more stand off of the brake cable (so it cleared the coupler), thus the stalks. I always mount the gear cable stops on stand offs to allow the barrel adjusters to be more easily turned with fingers. The stood off stops are self made.

Andrew R Stewart 

At the risk of thread drift- IIRC it's the A tank's surface area that controls the rate of gas use. More surface area more off gassing from the solution the A is dissolved into. So in theory (if I'm correct) a short but fat tank could have a greater rate of A flow then the same volume but with a tall skinny tank. Andy

guy153

Looks really nice. The only thing I would add is I try to put the cable stops on the tubes where they're still butted, which yours look like they probably are anyway. I arrange things so the longer butts of the TT and DT are near the HT end on the theory that you probably need a bit more strength up there anyway.

As for the gear cable stops I have used some cast ones similar to yours that attach about where DT shifters used to go. But some bikes have ones that attach directly to the HT itself-- they're usually sort of cone-shaped. That looks like a good design to me as the HT tends to be quite a thick tube and putting them up there means no rubbing.

mikeread

Front triangle is finished now and fillets rough filed. I didn't sleeve anywhere except the top of the seat tube. In the end I decided it was extra work (more to get wrong) and extra weight for no real gain.

I am now starting on the stays and have this morning rough mitered the top of the seat stays (Miter templates are brilliant thankyou Rattlecad :-)

I am not sure the best way to go about brazing this joint. I would like a nice clean joint and want to avoid filleting around the outside.

My plan was to make up some internal plugs for the seat stays to increase the joint surface area - see photo below - miter them with the stays and silver to the seat tube.

Does this sound like a good idea or an unnecessary complication?

Would the joint be strong enough without the plugs - silvered or brass? I would prefer to stick to silver as the top of the seat tube has already seen 2 heat cycles.

Your opinions and advice much appreciated as always :-)

unterhausen

are they side tack or fastback stays? Either way, you don't need to do anything other than fillet them on. The one complication with fastback stays is getting them too close to the seat post slot. Waterford sold a ton of bikes with fastback stays that were silvered at the top and broke. They blamed it on people that used a seatpost that was too small, I blame it on using silver.

duanedr 

I agree with Eric on both points - you don't need to use them but keep the stays away from the slot in any case.

As a counterpoint, I received a gift of a few boxes of various tubing. The builder had the tubes/fittings in his attic for 15-20 years from a previous production scale endeavor for brands and people we'd all likely recognize. Most of it was prototype bent chainstays and mitered tubes for abandoned prototype projects. There were a couple sets of seatstays that the tops were plugged and then machine mitered for fastback attachment. All of this to say that there is evidence of large-ish scale producers that use or have tried to use plugs in this joint. The large surface area provided by a plug of some kind, would be ideal for a thin layer of silver and no fillets as that is mainly a joint dealing with shear/compressive stresses.

Nessism

I like that idea of the sleeve inside the stay since as duanedr says, all you would have to do is silver them to the seat tube w/o fillet. That would save someone like me a fair bit of hassle because I like the joint to look clean but often am fearful of getting a good enough joint in that location.

mikeread

They are fast back style (on the back of the tube not the sides) and will be at least 10mm and max 20mm below the pucker hole. When I get the Miter correct, that is where they will go :-) Is that sufficient distance?

I would prefer to do this joint with silver and am not sure about filleting with silver, hence considering inserts instead of external fillets.

With the inserts, the joint area should be about 182 mm2 for each stay which is equivalent to a 14mm square. I suspect this is as much area as side mounted stays and to me the loading is more favorable too.

unterhausen

that's fine. The ones I talked about failing were actually beside the slot, so the pinch bolt moved the joint.

Andrew R Stewart 

I've not yet had a problem using silver on either shot in (fast back) or side of lug SS attachments on most of my frames. I do pay attention to how much surface contact there is, filing a groove in the lug's side to better nestle the stay end. And as mentioned the binder slot and it's stress relief key hole (and trying to keep the binder slot well over an inch long). I have used an internal sleeve to increase wall and contact surface at the stay ends only once, that I remember. I have begun to use thicker stay caps then just a tube cut off. (I make my own top eyes/caps, not a cast plug in). Andy

mikeread

I will go with the inserts, should get an hour or two this afternoon.

Thanks for the input everyone.

mikeread

This project has been on and off for a while but lockdown has given me the time to get it going again.

Frame is finished and I have decided to spray the frame myself using Spray Bike paint. The main coats are done, just waiting for some stencil materials to do the lettering then it just needs laquering.

The Spray Bike paint has been easy to use so far but I am not sure how durable it will be in use. I did have a small section lift off with the masking tape so I am not confident it has adhered too well.

I have over filed the fillets a little - despite taking great care. It looked fine until I applied the first coat of primer which somehow highlighted the problem. So I will ride this one just until the next one is finished :-)

Pics to follow:

guy153

Durability is improved a bit by putting the spray.bike clearcoat on which gives a bit more of a satin finish. It's nothing like as durable as powdercoat, but you can keep the can around and just touch it up when it needs it.

Also after painting it wait a couple of days before building the bike up. I would bring it indoors or somewhere warm if it's cold in your garage. As it's a brand new frame it should be exempt from any no bikes indoors policies that may be in force.

mikeread

I thought the clearcoat would help but not got that far yet.

Bikes are stored in the house - had that written into a pre-nup :-)

guy153

Very wise Not sure whether it's best to wait for the paint to dry completely before putting the clear on or only about 20 minutes.

The thing to watch out for with the clear is the solvent in it can end up dissolving the actual paint you already put on. You really need to keep your distance with the can and just sort of mist a bit on. Then do this several times over the next few days to gradually build it up. That worked for me anyway.

​​​

mikeread

Thanks Guy, that is worth knowing. The paint will have had a good few days to dry before adding clear - which will help prevent this I guess.

mikeread

The original plan was for the frame to be orange with small black areas. After spraying it orange, it was a bit 'too orange' so I added more black than originally intended. Not sure if I did the right thing as the large areas of black are a bit much! I still have to stencil the lettering on so I will do this in orange as big as I can to help break up the area of black. Otherwise I am quite pleased with the look.