Frame No 3
 

I am now starting to plan frame No 3 and have decided it is to be a long distance hill climbing machine. I have booked to ride the Raid Alpine next September which has motivated me to get started and gives me plenty of time to get it finished.

Frame No 2 has been great to ride so I am sticking with the same geometry and fork but plan to reduce the size of the top tube and seat tube from 2OS to OS. This is to soften the ride and will let me use a nice lightweight 27.2 titanium seatpost that I have to make things real comfy. HT will be 36 , DT 35 and stays will probably be Columbus Life again. All main tubes will be 8/5/8 or very close

I am a bit undecided how to join the tubes as matching lugs for the HT/TT 36/28.6 and ST/TT 28.6/28.6 junctions are not available for a sloping top tube. BBKT and DT/HT lugs are. It is a shame the Llewllyn lugs cannot be mixed and matched!

I am thinking maybe build it like this:

Make sleeves for the head tube (full length) and the top end of the seat tube
Fillet braze (with brass) the DT and TT to the sleeves.
Cut and shape the sleeves so you have a TT with a 'lug' at both ends and a DT with a 'lug' at the HT end.
Assemble the above with a HT and ST and conventional BBKT Lug and silver it all together.

Is it possible/worthwhile making the frame this way? what can go wrong? Has it been done this way before?

I am hoping it will allow me to use fillet joints without too much distortion in the head tube or seat tube. It should also make it easier to file and smooth the fillets.

Thanks

Mike

Google bilam frame. It involves fillet brazing a short section to the ht st doing something fancy to the short tube and inserting the tt, st, dt etc in the joined short tubes.

Other option buy the lug of choice cut to the angle you need and fillet braze the angle you need in the seat tube top head tube lug.

Mike could you clarify that you are wanting sleeves on both the head/seat tubes as well as on the ends of the top and down tube to create what looks like a lug? This was done by Claude Butler after WWII when lugs were scarce because industry had all been converted over to make stuff for the war effort. It has been common to do this bilaminate construction ever since.

There are several ways to create a bilam construction but I think the easiest is to carve the shape on the sleeve and then braze the sleeves onto the top and down tube and then miter the unit together ready to fillet braze those tubes to the head and seat tube.

It is also possible to do a half bilam construction where one sleeve is brazed only on one of the 2 tubes at a junction. Here is a picture of a frame one of my frame building class students made that required a sloping top tube. The cut sleeve on the head tube gave it distinction.https://cimg6.ibsrv.net/gimg/bikefor...eeec577069.jpg

Your picture shows pretty much the sort of thing I was planning Doug, but I was going to separate the two ends of the sleeve as I have a long head tube and don't want to add unnecessary weight.

However putting the sleeves on the TT and DT as you suggest and then filleting to the head tube means when filing the fillet the danger of over thinning the tubes is eliminated - a very attractive advantage which pretty much wipes out all my doubts about fillet brazing (see below) - which is a shame as that head tube looks the Dogs Bo##ox and I would love to do something similar. Using this method, could you silver the sleeves and then do the fillet in brass? I know some of the silver would melt but would this be a problem?

After fillet brazing my first frame (Reynolds 631) I started another in Columbus tubing, but scrapped it after finishing the front triangle as I was worried I had over thinned when filing the fillets. The Columbus tubing was much softer than the air hardening 631 had been.

Now I know it is called bilam construction I will do some googling.

If you contact Darrell directly he will sell you individual lugs. He has a sloping TT/ST lug that will work for your application but I don't see a sloping TT/HT lug for a 36mm HT and 28.6 TT.

Thanks for that but it is the HT/TT joint that is the problem.

I am pretty fixed on the Bilam construction anyway - for the time being :-)

When building a bilam like this is there brass/silver under the entire "lug"? Seems like a lot of real estate to fill.

thanks, Brian

The design of this frame was dictated by the fact she was a short woman (under 5') with shorter than average legs. You will notice that the down tube and top tube aren't very far apart. Then because her fit dictated that her handlebars were a little higher than her seat, the head tube had to be fairly long so she didn't have an ugly amount of stackers above the headset. Also because she needed smaller wheels that also extends the bottom of the head tube longer. She played around with a variety of designs and liked the look she came up with. I did too. So yes the whole area of the head tube sleeve was brazed with silver. She used fillet pro silver on the main triangle joints without any sleeves in the top or down tube, just on the head and seat tube.

my next frame is going to use the same tube sizes. I see Framebuilder supply sells tubes for horizontal top tubes. Not super happy with the styling. Pacenti used to have some lugs like that, but I guess they aren't being cast by anyone right now.

Just in case you didn't know (or for anybody else reading this thread), 0.058" wall tubing that can be bought at Wicks Aircraft or Aircraft Spruce are the sleeves you need to get for bilam construction. Ideally you can trim that thickness down on a lathe to 40 thousandths or less.

It is possible to silver the sleeves and bronze fillet braze the tubes together. Sometimes you might want to touch up the shorelines afterwards. Another option is using Fillet Pro silver from Cycle Design

Do you get any problems with the silver and brass interacting and do you still get an internal fillet?

I will do some test pieces when the time comes.

Regarding the chromoly sleeve tube, does anyone know a UK supplier that stocks the right sizes? Both places I have tried so far, list the sizes but do not stock them and are not prepared to order in small quantities.

Thanks
mike

Brian Chapman has quite a few photos of this technique on his Flickr site - and a movie even: https://flic.kr/p/2g9hnvd

William.

Silver on brass goes well. Good wet out and no issues with the brass changing. But doing brass mover silver can be more challenging with the higher temp brass needs and some flow out of silver possible. But where the silver and brass intermingle is no problem.

I would consider trying to make a lug and matching what's available for the other joints. Andy

I am going to do the whole lot bilam - except the bottom bracket. I cannot see the point of making full lugs, it just adds weight and work - I like the bilaminate look anyway :-)

Brian Chapman does silver into brass. IIRC, the frame Herbie Helm had at NAHBS in Richmond had the tubes into the bilaminate with silver then filleted together with brass. Doug can confirm.

Regarding tube sizing for bilam, what sizes would you use for a HT? For example, if a build would normally use a 36mm HT, would I use 1 5/8" .058 wall tubing for the sleeve? 36mm is 1.417 inches and the ID of 1 5/8" is 1.509.

Thanks.

Brandon

Too heavy (.97 vs .55 lb/ft) and too big a gap for me, other options c/be

1-1/2 od .035 wall thickness 1.430 ID

Or cut the pattern out of the head tube and put a liner inside the head tube around the cutout

Yes I thought the gap was a little too big as well. Heat control would have to be spot on for that .035 I would think.

Thanks for the info!

I have moved on a bit with this frame - at last, and have a question regarding the seat tube sleeve. Below is a mock up of the final layout, the seat tube will be cut off at the top of the sleeve.

I do not have any way of practicing brazing on the sleeve so I have to get it right first time. The sleeve is quite long (115mm top to point) I am worried about getting full penetration. So I am thinking as follows:

1 Drill as big a hole as possible in the sleeve under the top tube junction - maybe 20mm
2 Feed brass into this hole and work downwards until braze is seen at the bottom. Working down to minimise heat on the thin 0.6mm seat tube
3 Invert and do the top section


Does this sound practical? Would it be better to use brass or silver? - I will be filleting the top tube with brass
Am I worrying unnecessarily - might it be easier than I think?
Would it be better to shorten the top end of the sleeve to just beyond the tube junction and then use a seat-tube collar/clamp at the top and leave the bit in between 0.6mm?
Any other suggestions?

Thanks

Mike


https://cimg7.ibsrv.net/gimg/bikefor...336833d0e3.jpg

What you show is how I do most of my non-lugged frames.

I have tried drilling a TT vent hole and pucker hole in the sleeve before brazing it to the ST. I could then use those holes to add filler when brazing the sleeve onto the ST - to get full penetration with long sleeves . It required drilling the holes twice though.

I remember reading somewhere that some guys don't go for full penetration on the sleeve. Just soaking the filler in an inch or so was enough in their experience. Since I turn my sleeves down to around .040" I prefer to have full penetration. If I was leaving the walls at the full .058" (1.48mm!), I might feel differently.

I use 56% silver inside the sleeve. Silver keeps heat down minimizing distortion which makes reaming easier and it's easier to flow all the way through and to clean up the flux. Generally, I try to use silver for this whole joint except the binder boss. Just a lot of good stuff comes from using silver here.

Before I braze on the sleeve, I 'groove' it longitudinally with a course round file. You don't have to go crazy but a few hard strokes around the inside of the sleeve will create little channels to help the filler to wick down between the sleeve and ST. I would trim the excess from the top to save silver and make it easier to flow the filler through the sleeve. You could also shorten the part that extends below the TT for the same reasons. I have done a few that extend a couple inches below the TT and when I look at them now, they look a little out of proportion. The flip side is that a bit of extra length in the sleeve adds some mass so the TT fillet is a bit easier . Using brass on the TT fillet might make sense depending on how you attach the seatstays.

I like a point at the top of the seattube and contour both the ST and sleeve together as the final step before cutting the ST slot. If using a clamp, place the clamp on the outside of the sleeve, not on the .6mm walled seattube above the shoreline of the sleeve. I haven't really looked at what clamps sizes are available though so, that would be my first step. You don't want to cut the sleeve walls down then find there aren't any clamps that fit!

Thanks Duane

Not sure what you mean by 'pucker hole'? I guess it is the hole at the bottom of the seat tube slot?

Also I cannot figure why you would need to drill the TT vent hole twice?

I will drill and cut the seat tube slot in the sleeve before brazing (keeping the end closed) and then add the boss when everything else is done.

Yes, the hole at the bottom of the slot. The first drilling is a hole in the sleeve before brazing. I used the hole in the sleeve to add filler and then had to complete the hole in the actual tube with a 2nd drilling. Same thing for the pucker hole. This approach didn't seem to have any benefits and so I only tried it once with a longer sleeve.

There are many ways to skin this cat!

I practiced quite a bit to be able to get full penetration on those sleeves, finally realizing it is mostly a matter of having a really big tip on my torch and using a lot of heat. I use bronze. I am convinced full penetration is not necessary. An inch is probably too much too. OTOH, I'm pretty happy I figured out how to do it.

You could drill through the sleeve in various places to use as feed ports. After you are confident the sleeve has enough silver underneath then turn the frame, hole up, and put a blob of some thicker silver to mound over the hole (to be filed flat later.)

I’m going to second what Duane suggested and that is to shorten the sleeve. The bottom can come up a bit and so can the top come down. I think it would look better too. I’m sure you already know this but to others viewing the subject thread later, don’t cut the seat tube off to the sleeve until the very last thing after all brazing in that area is finished. That way if any more silver needs to be added to the shoreline or to smooth it out again, it is easy enough with the seat tube still sticking out beyond the sleeve.

I would use my rosebud tip to braze the sleeve to the seat tube. By holding the big flame back away from the joint a more even soaking heat can be applied without frying one area. If you don’t have a rosebud now you want to get one because they are great for taking things apart. One caution is that with a thick sleeve and a thin tube it is easy to bulge the seat tube out at the shoreline if it gets red. One can discover rookie brazing at the seat tube lug by sticking a finger inside and seeing if it bulges out anywhere. This doesn’t matter at the top because that gets cut off but it will at the bottom where your seat tube wall thickness is thin because it is not double butted up there.