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.



--
--------------------------
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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

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?

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

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

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

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

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