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Passive LWB homebuild drawings
Too many responsibilities and full time college, have prevent the
creation of a home site for my projects. However, perhaps other future builders can use the following links (drawings) to get them started. http://www.boomspeed.com/papasbent/Steel26_Sherpa.jpg http://www.boomspeed.com/papasbent/S..._Sherpa002.jpg http://www.boomspeed.com/papasbent/S..._Sherpa003.jpg http://www.boomspeed.com/papasbent/S..._Sherpa004.jpg http://www.boomspeed.com/papasbent/S..._Sherpa006.jpg http://www.boomspeed.com/papasbent/S..._Sherpa010.jpg I had to trash-can several files on the server to upload these, so no photos for a while. ************** snip ************ The technique is simple and straightforward. Please do not get saw crazy as most of the donor's frame will be used as a jig. First, you’ll need to locate a donor frame with specific top tube and down tube angles to achieve the desired head tube angle for the bent. The frames of choice are 13”-14” (BB to seat height) MTB frames. Many manufactures such as, Rocky Mountain, Trek 7000, C’Dale, and several others I’ve seen are beginning to show up in yard sales and second hand stores. Just look for the low “step-over” top tube. I used a couple of Canadian made Rocky Mountain Sherpa’s. These are double butted chromoly frames, so be careful welding/brazing as the tubes are .030 wall or less midway between ends. The top tube/head tube angle needs to be near 92 degrees and the down tube/head tube angle should be 65 to 66 degrees (assuming 59-60 degrees is the desired head tube angle for the finished product). Yes, the head tube will ultimately be inverted. Strip the donor frame and make ONE 1.5” diameter mitered (hole saw) cut in the TOP TUBE of the donor bike approx. 6.5” behind the head tube. From a second parts frame, cut out the BB shell leaving 5 or 6” of seat tube still attached. Grind-off any down-tube and chain stay stubs remaining on the BB shell. Now measure and miter the end of a parts bike seat tube/BB to the desired length (check the drawings) and tack weld it into position on the main donor bike. If you C-clamped and tack welded the BB shell into position, you can go ahead and weld it 360 degrees (to the forward 6” tube ONLY). Now trim-off an inch or so of the rear of the remaining donor's top tube (just behind the new BB shell you welded in). The second main donor frame cut will be via hack saw to the seat tube a few inches above the bike’s ORIGINAL BB shell. This cut will be slightly larger than the diameter of the chosen bent’s bottom tube. Miter ONE end of a 35”+ long tube and thread it between the original chain stays, through the 1.6” freshly cut seat tube, and butt its mitered end to the back side of the newly installed bottom bracket shell. Now C-clamp the 35 incher at the donor’s seat tube and again at the new BB shell and weld in place. Now you can cut away the original donor’s remaining seat tube and BB shell. All you need to do is to lengthen the 20” or so down tube (the bent’s top tube) and weld on the rear vertical end tube. The rear chain stays are fabricated from a rakeless (straight) mtb fork with brazed-on drop-outs. -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
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#2
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Passive LWB homebuild drawings
Thanks, those are interesting drawings.
Is it possible you would also have them in .dwg format? -- Lewis. http://tinyurl.com/r3r6 .......................... ******************************* "PaPa" wrote in message ... Too many responsibilities and full time college, have prevent the creation of a home site for my projects. However, perhaps other future builders can use the following links (drawings) to get them started. http://www.boomspeed.com/papasbent/Steel26_Sherpa.jpg http://www.boomspeed.com/papasbent/S..._Sherpa002.jpg http://www.boomspeed.com/papasbent/S..._Sherpa003.jpg http://www.boomspeed.com/papasbent/S..._Sherpa004.jpg http://www.boomspeed.com/papasbent/S..._Sherpa006.jpg http://www.boomspeed.com/papasbent/S..._Sherpa010.jpg I had to trash-can several files on the server to upload these, so no photos for a while. ************** snip ************ The technique is simple and straightforward. Please do not get saw crazy as most of the donor's frame will be used as a jig. First, you'll need to locate a donor frame with specific top tube and down tube angles to achieve the desired head tube angle for the bent. The frames of choice are 13"-14" (BB to seat height) MTB frames. Many manufactures such as, Rocky Mountain, Trek 7000, C'Dale, and several others I've seen are beginning to show up in yard sales and second hand stores. Just look for the low "step-over" top tube. I used a couple of Canadian made Rocky Mountain Sherpa's. These are double butted chromoly frames, so be careful welding/brazing as the tubes are .030 wall or less midway between ends. The top tube/head tube angle needs to be near 92 degrees and the down tube/head tube angle should be 65 to 66 degrees (assuming 59-60 degrees is the desired head tube angle for the finished product). Yes, the head tube will ultimately be inverted. Strip the donor frame and make ONE 1.5" diameter mitered (hole saw) cut in the TOP TUBE of the donor bike approx. 6.5" behind the head tube. From a second parts frame, cut out the BB shell leaving 5 or 6" of seat tube still attached. Grind-off any down-tube and chain stay stubs remaining on the BB shell. Now measure and miter the end of a parts bike seat tube/BB to the desired length (check the drawings) and tack weld it into position on the main donor bike. If you C-clamped and tack welded the BB shell into position, you can go ahead and weld it 360 degrees (to the forward 6" tube ONLY). Now trim-off an inch or so of the rear of the remaining donor's top tube (just behind the new BB shell you welded in). The second main donor frame cut will be via hack saw to the seat tube a few inches above the bike's ORIGINAL BB shell. This cut will be slightly larger than the diameter of the chosen bent's bottom tube. Miter ONE end of a 35"+ long tube and thread it between the original chain stays, through the 1.6" freshly cut seat tube, and butt its mitered end to the back side of the newly installed bottom bracket shell. Now C-clamp the 35 incher at the donor's seat tube and again at the new BB shell and weld in place. Now you can cut away the original donor's remaining seat tube and BB shell. All you need to do is to lengthen the 20" or so down tube (the bent's top tube) and weld on the rear vertical end tube. The rear chain stays are fabricated from a rakeless (straight) mtb fork with brazed-on drop-outs. -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
#3
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Passive LWB homebuild drawings
PaPa wrote in message ...
Too many responsibilities and full time college, have prevent the creation of a home site for my projects. However, perhaps other future builders can use the following links (drawings) to get them started. http://www.boomspeed.com/papasbent/Steel26_Sherpa.jpg http://www.boomspeed.com/papasbent/S..._Sherpa002.jpg http://www.boomspeed.com/papasbent/S..._Sherpa003.jpg http://www.boomspeed.com/papasbent/S..._Sherpa004.jpg http://www.boomspeed.com/papasbent/S..._Sherpa006.jpg http://www.boomspeed.com/papasbent/S..._Sherpa010.jpg I had to trash-can several files on the server to upload these, so no photos for a while. ************** snip ************ The technique is simple and straightforward. Please do not get saw crazy as most of the donor's frame will be used as a jig. First, you?ll need to locate a donor frame with specific top tube and down tube angles to achieve the desired head tube angle for the bent. The frames of choice are 13?-14? (BB to seat height) MTB frames. Many manufactures such as, Rocky Mountain, Trek 7000, C?Dale, and several others I?ve seen are beginning to show up in yard sales and second hand stores. Just look for the low ?step-over? top tube. I used a couple of Canadian made Rocky Mountain Sherpa?s. These are double butted chromoly frames, so be careful welding/brazing as the tubes are .030 wall or less midway between ends. The top tube/head tube angle needs to be near 92 degrees and the down tube/head tube angle should be 65 to 66 degrees (assuming 59-60 degrees is the desired head tube angle for the finished product). Yes, the head tube will ultimately be inverted. Strip the donor frame and make ONE 1.5? diameter mitered (hole saw) cut in the TOP TUBE of the donor bike approx. 6.5? behind the head tube. From a second parts frame, cut out the BB shell leaving 5 or 6? of seat tube still attached. Grind-off any down-tube and chain stay stubs remaining on the BB shell. Now measure and miter the end of a parts bike seat tube/BB to the desired length (check the drawings) and tack weld it into position on the main donor bike. If you C-clamped and tack welded the BB shell into position, you can go ahead and weld it 360 degrees (to the forward 6? tube ONLY). Now trim-off an inch or so of the rear of the remaining donor's top tube (just behind the new BB shell you welded in). The second main donor frame cut will be via hack saw to the seat tube a few inches above the bike?s ORIGINAL BB shell. This cut will be slightly larger than the diameter of the chosen bent?s bottom tube. Miter ONE end of a 35?+ long tube and thread it between the original chain stays, through the 1.6? freshly cut seat tube, and butt its mitered end to the back side of the newly installed bottom bracket shell. Now C-clamp the 35 incher at the donor?s seat tube and again at the new BB shell and weld in place. Now you can cut away the original donor?s remaining seat tube and BB shell. All you need to do is to lengthen the 20? or so down tube (the bent?s top tube) and weld on the rear vertical end tube. The rear chain stays are fabricated from a rakeless (straight) mtb fork with brazed-on drop-outs. Looks real neat but, isn't the front derailluer post at too vertical of an angle to get decent shifting? |
#4
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Passive LWB homebuild drawings
Originally posted by Lewis Campbell Thanks, those are interesting
drawings. Is it possible you would also have them in .dwg format? -- Lewis. http://tinyurl.com/r3r6http://tinyurl.com/r3r6 ......................... ******************************* Lewis, All are DXF, because I work with three different CAD programs. What'cu thinkin'? -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
#5
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Passive LWB homebuild drawings
Robert Box wrote:
PaPa wrote in message ... Looks real neat but, isn't the front derailluer post at too vertical of an angle to get decent shifting? Robert, Not for the derailleur i use. Even so, you can install the vertical derailleur tube shown at any reasonable angle you wish during construction. -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
#6
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Passive LWB homebuild drawings
To all, The drawings were posted with the expectation that individual
changes would likely be made. Since server space is extremely limited, I uploaded what I felt were the most important. If anyone needs an accurate, but very user friendly CAD program to make mods, then snap a copy of this 3.8mb gem: http://dcad.com/ Not only will it do DXF, but it'll also import and export BMP images. -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
#7
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Passive LWB homebuild drawings
Well, I have an IntelliCAD program ( www.cadopia.com ) and I was wondering
if I might be able to talk you out of a set of those drawings that I could play with. Kind regards. -- Lewis. http://tinyurl.com/r3r6 .......................... ******************************* "PaPa" wrote in message ... Originally posted by Lewis Campbell Thanks, those are interesting drawings. Is it possible you would also have them in .dwg format? -- Lewis. http://tinyurl.com/r3r6http://tinyurl.com/r3r6 ......................... ******************************* Lewis, All are DXF, because I work with three different CAD programs. What'cu thinkin'? -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
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Passive LWB homebuild drawings
Just a brief addition, then gotta run.
Some have expressed concerns about the stubby derailleur tube. I simply brazed-on a derailleur mount. Or, if the builder is lucky enough to find a donor frame with a longer head tube (the Sherpa headtube shown is 3.5"). Care should exercised as this will effective lower the BB shell, and/or elevate and change the top tube angle. 2. Use a braze-on derailleur mount. The dimensions shown are suitable for shorter riders such as myself. If your x-seam is much over 39", then lengthen the bottom and top tubes accordingly (2 to 3 inches wouldn't hurt). -- -------------------------- Posted via cyclingforums.com http://www.cyclingforums.com |
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