So I figured I would share what I am doing/have done for my 2nd frame for anyone interested - I have learned a decent amount from this forum and welcome any feedback or criticism you may have.
Geometry for the frame is shown below here:
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I chose a relatively short chainstay length because the CS of my first was too long for what I liked (I based the first frame off of my name brand FS which didn't work out so good in many aspects). But the 406mm number in the drawing is with the sliding dropouts all of the way forward, so really it can be set between 406 and ~420mm.
I would have preferred the seat tube angle be a little slacker, but by the time I realized that, I had already bent/mitered the tube and decided to just run it for now, take note of it, and adjust things as needed next time around.
The tubing in general is on the thicker end (mostly Nova or Vari-Wall 1-.7-1 or 1-.7-.9) with a straight gauge 0.035" ST + Topper and PMW Headtube/BB Shell (thicker option); all which seem to work good for my welding skill. Currently I weld with the pulser set to ~50PPS, 25-30% On Time, 25-30% background current and dab rod as if welding straight current... I don't know if pulsing at this high a frequency actually does anything for me, but in my mind it seems at least a little easier than straight current. I have been playing around with other settings more frequently suggested in these forums (such as 1-2PPS) on scrap/practice tubing and may try things that way the next time around to see how it works for me.
Because I would like to run 3" tires (actual width measures 2.85"), I decided to make a yoke for the chainstays. These are made from 5mm thick 4130 plate, cut to 36mm tall and bent with a milling vice between an Aluminum round and scrap tubing. In CAD I thought this looked reasonable, was achievable for me to make and, with the bridge/bends thought it would be stiff enough... But it was a nightmare for me to weld up and when I was done, I found that I could move the dropouts around laterally (and plastically) incredibly easily... I am hoping that with the addition of the Seat Stays and SS Bridge the rear end will stiffen this up enough for me to ride without permanent deformation to one side... I guess time will tell.
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The majority of the welds (minus the CS Yoke) turned out pretty decent for me, which I was pretty happy about, and the PMW headtube stayed thoroughly round through my heat input (which was nice, I had problems keeping the straight gauge, 1.25mm HT Stock round). The HT is 125mm long and I will be running a 160mm 27.5+/29 Fork on this. I opted for a 66 degree Head Angle for this bike with a fork sag of 40mm (25%)... I don't really know the best sag point to base this on, nor what Head Angle I really want with this type of bike. My first frame was a 67 Degree Head Angle which I kind of liked, but it was fully rigid and I was intimidated to go any slacker on my first frame. This time around I decided slacker would be nice, and somehow settled on what is shown above.
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At this point in time - the frame is all done with welding. The best method that I have to check alignment is in the 8020 jig that I made, which does show a little bit of HT Twist and mis-alignment of the ST as shown below. I have heard of additional welding passes some people will do to correct this, but I am not sure exactly how to accomplish that without potentially making it worse, and think I have decided to just ride it as it and try and control my heat/improve my welding sequence and mitering as much as I can on the next frame.
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At this point - I really just have smaller details left to finish. Several H20 Bosses to braze into the front triangle (for bottles + cable routing), zip tie cable mounts to braze to the rear triangle, and need to figure out how exactly I want to attack the routing into the ST for the internal dropper post cable (I bought a few a cheap internal cable route cover braze on things from Nova but am thinking I may just cut out a piece of stainless sheet and silver braze on for reinforcing and then drill...). I am not good at brazing and have yet to purchase an OA setup so I have been playing around with MAPP for these small items on scrap (and yes I know that several of you will hate me for saying that) - it seems to works OK I guess for silver and H20 bosses but then again I don't really have a good reference point. Anyway, I will do some more practice brazing and probably finish this frame out with the tools I have on hand currently.
Oh and I guess for reference, since I mentioned it several times, below is a pic of my first frame. I built this ~ a year ago and have been riding it anytime I ride with the kids or dog (pretty much always except when I go by myself/with friends to faster/more technical trails). It's not amazing by any means but has been really fun to ride and try and learn from.
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-AP
Geometry for the frame is shown below here:
I chose a relatively short chainstay length because the CS of my first was too long for what I liked (I based the first frame off of my name brand FS which didn't work out so good in many aspects). But the 406mm number in the drawing is with the sliding dropouts all of the way forward, so really it can be set between 406 and ~420mm.
I would have preferred the seat tube angle be a little slacker, but by the time I realized that, I had already bent/mitered the tube and decided to just run it for now, take note of it, and adjust things as needed next time around.
The tubing in general is on the thicker end (mostly Nova or Vari-Wall 1-.7-1 or 1-.7-.9) with a straight gauge 0.035" ST + Topper and PMW Headtube/BB Shell (thicker option); all which seem to work good for my welding skill. Currently I weld with the pulser set to ~50PPS, 25-30% On Time, 25-30% background current and dab rod as if welding straight current... I don't know if pulsing at this high a frequency actually does anything for me, but in my mind it seems at least a little easier than straight current. I have been playing around with other settings more frequently suggested in these forums (such as 1-2PPS) on scrap/practice tubing and may try things that way the next time around to see how it works for me.
Because I would like to run 3" tires (actual width measures 2.85"), I decided to make a yoke for the chainstays. These are made from 5mm thick 4130 plate, cut to 36mm tall and bent with a milling vice between an Aluminum round and scrap tubing. In CAD I thought this looked reasonable, was achievable for me to make and, with the bridge/bends thought it would be stiff enough... But it was a nightmare for me to weld up and when I was done, I found that I could move the dropouts around laterally (and plastically) incredibly easily... I am hoping that with the addition of the Seat Stays and SS Bridge the rear end will stiffen this up enough for me to ride without permanent deformation to one side... I guess time will tell.
The majority of the welds (minus the CS Yoke) turned out pretty decent for me, which I was pretty happy about, and the PMW headtube stayed thoroughly round through my heat input (which was nice, I had problems keeping the straight gauge, 1.25mm HT Stock round). The HT is 125mm long and I will be running a 160mm 27.5+/29 Fork on this. I opted for a 66 degree Head Angle for this bike with a fork sag of 40mm (25%)... I don't really know the best sag point to base this on, nor what Head Angle I really want with this type of bike. My first frame was a 67 Degree Head Angle which I kind of liked, but it was fully rigid and I was intimidated to go any slacker on my first frame. This time around I decided slacker would be nice, and somehow settled on what is shown above.
At this point in time - the frame is all done with welding. The best method that I have to check alignment is in the 8020 jig that I made, which does show a little bit of HT Twist and mis-alignment of the ST as shown below. I have heard of additional welding passes some people will do to correct this, but I am not sure exactly how to accomplish that without potentially making it worse, and think I have decided to just ride it as it and try and control my heat/improve my welding sequence and mitering as much as I can on the next frame.
At this point - I really just have smaller details left to finish. Several H20 Bosses to braze into the front triangle (for bottles + cable routing), zip tie cable mounts to braze to the rear triangle, and need to figure out how exactly I want to attack the routing into the ST for the internal dropper post cable (I bought a few a cheap internal cable route cover braze on things from Nova but am thinking I may just cut out a piece of stainless sheet and silver braze on for reinforcing and then drill...). I am not good at brazing and have yet to purchase an OA setup so I have been playing around with MAPP for these small items on scrap (and yes I know that several of you will hate me for saying that) - it seems to works OK I guess for silver and H20 bosses but then again I don't really have a good reference point. Anyway, I will do some more practice brazing and probably finish this frame out with the tools I have on hand currently.
Oh and I guess for reference, since I mentioned it several times, below is a pic of my first frame. I built this ~ a year ago and have been riding it anytime I ride with the kids or dog (pretty much always except when I go by myself/with friends to faster/more technical trails). It's not amazing by any means but has been really fun to ride and try and learn from.
-AP
