You do not want to go much higher. You want the bottom of the seatpost to insert below the top tube.
External sleeve gusset/lug question
What is the best way of going about something like this:
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?
I want to do this type of thing, but have the external part extend up much further (i.e. seat mast)
Should I brass braze the two together at the lower edge and not worry about where the inner tube ends? Or should I tack it with brass and then fill it with silver after the tt & ss are attached? Or maybe something else?
I want to do this type of thing, but have the external part extend up much further (i.e. seat mast)
Should I brass braze the two together at the lower edge and not worry about where the inner tube ends? Or should I tack it with brass and then fill it with silver after the tt & ss are attached? Or maybe something else?
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Thoughts
If you want a mast, you can pretty easily do it the way you're describing, but you'll need a 28.6 seatpost stub (if you go that route), and it's going to be *really* heavy, because you'll be using 1 1/4"x.058" tubing for the mast/sleeve, which is WAY heavy. It will also probably be monstrously unforgiving when seated, since that massive mast isn't going to flex much/at all.
I would make sure the actual seat tube extends at least an inch above the toptube/seatstay cluster, and I'd braze it together first with silver (if you're fillet brazing) then lay your fillets on top of the sleeve as normal.
-Walt
If you want a mast, you can pretty easily do it the way you're describing, but you'll need a 28.6 seatpost stub (if you go that route), and it's going to be *really* heavy, because you'll be using 1 1/4"x.058" tubing for the mast/sleeve, which is WAY heavy. It will also probably be monstrously unforgiving when seated, since that massive mast isn't going to flex much/at all.
I would make sure the actual seat tube extends at least an inch above the toptube/seatstay cluster, and I'd braze it together first with silver (if you're fillet brazing) then lay your fillets on top of the sleeve as normal.
-Walt
My plan was to use a 25.4mm seattube with 1 1/8"x.058" tubing for the mast/sleeve, and probably for a sleeve on the st at the bb (for stiffness), with a 25.4mm stub of a seatpost. As best I can tell, it'll only add about 60-80 grams over the weight of a non-seatmasted frame. Subtract the weight of most of a seatpost, and it seems fine to me.Walt said:If you want a mast, you can pretty easily do it the way you're describing, but you'll need a 28.6 seatpost stub (if you go that route), and it's going to be *really* heavy, because you'll be using 1 1/4"x.058" tubing for the mast/sleeve, which is WAY heavy. It will also probably be monstrously unforgiving when seated, since that massive mast isn't going to flex much/at all.
I would make sure the actual seat tube extends at least an inch above the toptube/seatstay cluster, and I'd braze it together first with silver (if you're fillet brazing) then lay your fillets on top of the sleeve as normal.
-Walt
If I silver braze the seattube and the sleeve/mast together first, won't it all melt out before I get it up to temp for the brass brazing of the tt and ss?
well i guess i'll chime in as that is one of my bikes! it's a 1.25"OD x .058" x 3 & 7/8" long piece of 4130 mitered with a 1.5" holesaw. the ST goes all the way through. it's brazed 1st with 56% then brazed. no melting of the 56% if you get in & get out quick. Steve Garro, Coconino Cycles.
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Pretend I said what Hand/of/Midas just said. He left himself signed in at work, and I can't seem to figure out how to delete a post.
Seems like most recommend using silver to braze these sleeves. What would be the issue with using standard brass? Is it just that it's easier to do these lug-type add-ons with silver?
Thanks for the imput Steve. I've been thinking about this for a while, and this was the best example I could find.coconinocycles said:well i guess i'll chime in as that is one of my bikes! it's a 1.25"OD x .058" x 3 & 7/8" long piece of 4130 mitered with a 1.5" holesaw. the ST goes all the way through. it's brazed 1st with 56% then brazed. no melting of the 56% if you get in & get out quick. Steve Garro, Coconino Cycles.
I still don't understand how the silver doesn't all melt out durring the tt/st brazing. I guess I'll just trust you guys, though. Will this be a problem for me if I have yet to gain "pro status" in brazing/framebuilding?
Some basic assumptions
I'm assuming you're not going to run a front derailleur, since your 25.4 seat tube won't easily work with one anyway. I'd definitely use straightgauge for that seat tube, too - 25.4 butted is a pretty bad idea for a mountain bike toptube, let alone a seat tube.
If you've got, say, 250mm of post/mast sticking out (and the sleeve extends, say 75mm below that), the 28.6x.058x325mm weighs 280g. The head/stub is going to weigh at least 60 or 70, so you're already at 350g - which is a damn porky seatpost. Heck, a $10 Kalloy is lighter than that by a significant amount. And it still needs a collar and such, just like a conventional setup.
If you want to do it because you think it's just plain cool, do it. Otherwise, don't bother. It doesn't get you anything you don't already have with a regular seatpost, and it's quite a bit heavier and less adjustable.
BTW, you should be able to lay the fillet without getting the *entire* sleeve so hot that the silver melts out (if you can't, you should be making practice joints, not bikes). It will melt directly under the fillet, of course, but it doesn't have anywhere to go and will just re-solidify afterwards.
-Walt
I'm assuming you're not going to run a front derailleur, since your 25.4 seat tube won't easily work with one anyway. I'd definitely use straightgauge for that seat tube, too - 25.4 butted is a pretty bad idea for a mountain bike toptube, let alone a seat tube.
If you've got, say, 250mm of post/mast sticking out (and the sleeve extends, say 75mm below that), the 28.6x.058x325mm weighs 280g. The head/stub is going to weigh at least 60 or 70, so you're already at 350g - which is a damn porky seatpost. Heck, a $10 Kalloy is lighter than that by a significant amount. And it still needs a collar and such, just like a conventional setup.
If you want to do it because you think it's just plain cool, do it. Otherwise, don't bother. It doesn't get you anything you don't already have with a regular seatpost, and it's quite a bit heavier and less adjustable.
BTW, you should be able to lay the fillet without getting the *entire* sleeve so hot that the silver melts out (if you can't, you should be making practice joints, not bikes). It will melt directly under the fillet, of course, but it doesn't have anywhere to go and will just re-solidify afterwards.
-Walt
Hand/of/Midas said:My plan was to use a 25.4mm seattube with 1 1/8"x.058" tubing for the mast/sleeve, and probably for a sleeve on the st at the bb (for stiffness), with a 25.4mm stub of a seatpost. As best I can tell, it'll only add about 60-80 grams over the weight of a non-seatmasted frame. Subtract the weight of most of a seatpost, and it seems fine to me.
If I silver braze the seattube and the sleeve/mast together first, won't it all melt out before I get it up to temp for the brass brazing of the tt and ss?
this is the truth. 100%. Steve Garro, Coconino Cycles.Walt said:BTW, you should be able to lay the fillet without getting the *entire* sleeve so hot that the silver melts out (if you can't, you should be making practice joints, not bikes).
-Walt
Ok, so what this is going on is actually going to be a CX/touring type bike (I know I'm on the wrong forum). It's going to have a horizontal tt, so the mast portion will only need to be about 5" above the tt, so it won't be as heavy as if it were going on a mountain bike and it won't have as much leverage.Walt said:I'm assuming you're not going to run a front derailleur, since your 25.4 seat tube won't easily work with one anyway. I'd definitely use straightgauge for that seat tube, too - 25.4 butted is a pretty bad idea for a mountain bike toptube, let alone a seat tube.
If you've got, say, 250mm of post/mast sticking out (and the sleeve extends, say 75mm below that), the 28.6x.058x325mm weighs 280g. The head/stub is going to weigh at least 60 or 70, so you're already at 350g - which is a damn porky seatpost. Heck, a $10 Kalloy is lighter than that by a significant amount. And it still needs a collar and such, just like a conventional setup.
If you want to do it because you think it's just plain cool, do it. Otherwise, don't bother. It doesn't get you anything you don't already have with a regular seatpost, and it's quite a bit heavier and less adjustable.
BTW, you should be able to lay the fillet without getting the *entire* sleeve so hot that the silver melts out (if you can't, you should be making practice joints, not bikes). It will melt directly under the fillet, of course, but it doesn't have anywhere to go and will just re-solidify afterwards.
-Walt
Oh, and I mostly want to do this mast because my friend (who the bike is for) thinks it looks cool.
I planned on using a braze-on front derailleur mount so I didn't have to worry about the clamp diameter.
Being that it is a CX/touring bike for a "light" (160-ish lb.) rider, do you still think it's a bad idea to use a butted 25.4 seattube?
What you're saying about the silver having no where to go totally makes sense to me. My next question is, though, what do I do at the bb (or on a dt at the ht) when the silver DOES have somewhere to go?
What?
I thought this was going to be a fillet bike. Why is there going to be silver at the DT/HT or BB shell?
I would not use a 25.4 tube on anything but a road bike for a really tiny person. Bigger than tiny person, or used on dirt, or loaded for touring, no way. In this case you've got all three.
At this point I have to ask (and I'm not trying to be a jerk) have you ever built a frame? If not, you're being a bit ambitious, IMO.
-W
I thought this was going to be a fillet bike. Why is there going to be silver at the DT/HT or BB shell?
I would not use a 25.4 tube on anything but a road bike for a really tiny person. Bigger than tiny person, or used on dirt, or loaded for touring, no way. In this case you've got all three.
At this point I have to ask (and I'm not trying to be a jerk) have you ever built a frame? If not, you're being a bit ambitious, IMO.
-W
A-Town212 said:Ok, so what this is going on is actually going to be a CX/touring type bike (I know I'm on the wrong forum). It's going to have a horizontal tt, so the mast portion will only need to be about 5" above the tt, so it won't be as heavy as if it were going on a mountain bike and it won't have as much leverage.
Oh, and I mostly want to do this mast because my friend (who the bike is for) thinks it looks cool.
I planned on using a braze-on front derailleur mount so I didn't have to worry about the clamp diameter.
Being that it is a CX/touring bike for a "light" (160-ish lb.) rider, do you still think it's a bad idea to use a butted 25.4 seattube?
What you're saying about the silver having no where to go totally makes sense to me. My next question is, though, what do I do at the bb (or on a dt at the ht) when the silver DOES have somewhere to go?
Sorry, I should have been more specific. Yes, it will be a fillet bike. I was refering to doing a sleeve gusset on the dt at the ht.Walt said:I thought this was going to be a fillet bike. Why is there going to be silver at the DT/HT or BB shell?
I would not use a 25.4 tube on anything but a road bike for a really tiny person. Bigger than tiny person, or used on dirt, or loaded for touring, no way. In this case you've got all three.
At this point I have to ask (and I'm not trying to be a jerk) have you ever built a frame? If not, you're being a bit ambitious, IMO.
-W
Yes, I have build A bike before. I attended UBI in Ashland, OR last month. Ambitious is kind of my style. Don't worry, though, I have plenty of tubing for practice before anyone rides anything I make.
Why?
Why do you want a sleeve on the downtube? Just use an appropriate tube, join it well, and it won't break. Touring bikes don't usually need gussets.
This is my last piece of advice: build your friend a nice conventional fillet brazed steel touring bike. He'll love it. Do weird stuff later after you've figured out the normal stuff.
-Walt
Why do you want a sleeve on the downtube? Just use an appropriate tube, join it well, and it won't break. Touring bikes don't usually need gussets.
This is my last piece of advice: build your friend a nice conventional fillet brazed steel touring bike. He'll love it. Do weird stuff later after you've figured out the normal stuff.
-Walt
A-Town212 said:Sorry, I should have been more specific. Yes, it will be a fillet bike. I was refering to doing a sleeve gusset on the dt at the ht.
Yes, I have build A bike before. I attended UBI in Ashland, OR last month. Ambitious is kind of my style. Don't worry, though, I have plenty of tubing for practice before anyone rides anything I make.
Silver flows into the tight spaces better than brass/bronze, and at a lower temp.jocko said:Seems like most recommend using silver to braze these sleeves. What would be the issue with using standard brass? Is it just that it's easier to do these lug-type add-ons with silver?
Yup. And this is my future bike in discussion,BTW.A-Town212 said:Pretend I said what Hand/of/Midas just said. He left himself signed in at work, and I can't seem to figure out how to delete a post.
I accept the weight penalty of the seat mast, this is steel, not carbon anyway. 5lb and i'm happy. I'm really light on bike abuse too.
If my bike turns out HALF as nice as the one he built for himself i'll be more then stoked.
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