RECYCLED
RECUMBENT!!!! 
Guide to Long Wheel Base home built bike!!!
RECYCLED
Guide to Long Wheel Base home built bike!!!
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New and old BIKES BY OTHERS!!!!
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Use
these notes in reference to the MACH 2 bike drawings. First,
the page system. The sheets on
the MACH 2
DRAWINGS page SUBSTITUTE into the
EZ Clone sequence. Use Sheet
#11, instead of Sheet #1. There
is no sheet #12, so use Sheet #2 from the original set.
And so on to make a new packet of sequenced drawings.
This presumes you printed them all out.
Each image here is intended to be printed as large as possible on 8 ½”
by 11” paper. Go here for PDF
downloadable versions of the sheets - DRAWINGS
DESIGN
GOALS.
The principle change of the Mach 2 bike is to flip the head tube
in the frame assembly. Depending
on the donor bike, this results in a more acute head tube angle for the
recumbent bike, which reduces the ‘tiller’ effect in steering.
This improves the handling at the top end.
But there are consequences. That
sharp a head tube angle requires you to add considerable rake to the front
forks. The added rake corrects
the ‘flop’ in the steering caused by making the head angle so sharp.
This added rake actually lowers the bike closer to the road, which
means we have to make the frame design narrower (reduce the overall height of
the bike frame) to keep the crank far enough off the ground.
No heel scraping allowed, even in the tight turns.
The new bike is better handling, by a dramatic little bit.
It feels better because you don’t have to swing the steering handlebars
out so far to accomplish a tight turn.
The Mach 2 looks distinctly different too – you can see the narrower
height of the frame, and the head tube is sharper in angle than the old seat
tube right behind it.
The differences between the two designs are subtle, and unlikely to
matter much to a beginning rider just learning to ride recumbent.
After 1000 miles, it will matter to you.
The differences in building the two designs are acute.
I am telling you – build the EZ Clone first, learn from it.
Build this bike later, with the lessons learned from the first bike.
The EZ Clone is very forgiving to first time layout and alignment
mistakes. The Mach 2 is a
harsher mistress. SHEET
11 -
This is a different cut than the work you did on sheet #1.
Instead of using all of the top tube from bike 1, we use just enough of
it (we will trim it more a little later) to be our downtube in the flipped
assembly. Cutting off
the rear triangle is the same as for the first bike. SHEET
12 – there is no Sheet #12, the cuts
are the same as on Sheet 2. SHEET
13A – Fork bending.
In general, about 4 1/2” of fork rake is needed on this bike.
The fork from a donor bike has (usually) 2” or 2 1/8” of rake.
A 3/4” conduit bender works
very nicely to bend fork blades. AGAIN, put the bender in a bench vice and move
the fork, not the bender. The pictures show the wrong
way to do this (on the floor). Use a salvaged piece of 1 1/8" bike
tubing as an extension on the head tube for leverage, and bend away! Notch
the fork leg into the bender right at the drop out and BEND a good 2” –
roughly. Take pains to keep
the fork blade centered, and the fork crown level.
Try to match your bend with the second fork blade.
You can measure the change by laying the fork on any flat table.
Check the evenness of your bends by the reverse test shown in the drawing
– both drop outs should touch at the same time – no rocking allowed.
Expect to adjust on one blade or the other.
Take some time with this – if you have a spare fork or two (from other
donor bikes), do a practice run first.
There are formulas for deciding exactly how much trail is right for a
given head tube angle. Unless
you are set up for some real precision measuring, this rough alignment will do
just fine. Check the pictures on Picture
Page 4 SHEET
13A2 – Fork bending.
I just added this sheet as a second test for checking your newly raked
fork. Draw the indicated
parallel lines – a center line with lines ½” away on either side, a pair of
key lines 100mm (3 15/16”) apart, with some parallel lines either side of
that. 100mm is the typical
spacing for a front wheel axle. After
you are happy with the rake and the table top test above, set your fork down on
this pattern. Put the curve
arc up – the fork is resting on the end of it’s stem and on the two drop
outs. Look down from directly
over the fork, visually align the top of the head tube on that center line,
place the two drop outs on the 100mm lines down the way.
NOW sight through the old brake mounting hole in the fork crown.
Is it on the center line? You
are lucky if so. Are the
dropouts the proper distance apart?
Time to adjust. You need this
finiky alignment, or your front end will want to stray right or left when you
ride. Centered and balanced.
It’s hard to do, and just as important as the rear wheel alignment.
I make adjustments here by clamping the fork blade in my vice just below
the crown. Then I (with an
extension tube over the stem) and push and pull the fork into alignment for this
test. Get happy with it.
Then, go BACK to the table top test and make sure the rake is even again.
And check this again too! SHEET
13B – Layout.
Here you get to decide how long to make the final downtube dimension.
Use the real parts. Take your
time with this - use that fork you just bent, with the 20” wheel in it.
Use the Frame #1’s parts – Put the fork into the headset, put the
wheel into the drop outs on the fork. Take the piece with the
bottom bracket and position this over the assembled parts on the table.
Have a donor crank in hand, Handle this along with that bottom bracket
piece - test your layout now. There
is a picture of this on Picture
Page 1. Here is the question –
how short can you make that finished downtube without the crank interfering with
either the front tire or the fork? Is
there still enough room on the uptube (the one we will cut off later to fit
under the top tube) to hang a front derailleur?
I have been making my finished down tubes about 8” now where the
drawing shows 9”. Make
it as narrow as you can while maintaining clearances – your crank height will
thank you later. SHEET
13C – Shows the same assembly drawing
as we saw on the original Sheet #3. Except
that the head tube in this arrangement is flipped upside down.
What was the donor bike’s top tube is now the new bike’s down tube,
sleeving into the stub of the bottom bracket.
What was the donor bike’s down tube is now the new bike's top tube. OK?
Trim the NEW downtube to sleeve into the stub at the bottom bracket at
the ordained height from the layout in 13B.
Trim and fishmouth the up tube from the bottom bracket to snug up under
the new top tube. Braze/weld
joints as in the earlier bike. There
is a picture of this too in the sequence
Second assembly is just like the EZ Clone, except that our ‘splice’
joint is here on the top tube, instead of on the down tube.
Set the length of the bike to your preference.
Make sure everything is in plane and braze/weld away!
Mark Stonich suggested to me that, on a splice joint like this, one
should braze one end of it into the outer tube first.
Then clean that up, insert onto the second tube (and do the alignment),
and braze that in place second. Mark
is wise. SHEET
14 – The principal difference between
this and Sheet #4 is that you bend the rear triangle a bit farther – a new
dimension here. Otherwise, the
offset for the top stays, and the layout and alignment of the rear triangle to
the bike frame, is exactly the same as on Sheet #4.
The Clones are a forgiving geometry, but the more time and effort you put
into this alignment, the better your bike will be.
See alignment notes and methods in EZ Clone notes section! SHEET
15 – The final assembly with ¾” EMT
bottom rails is the same as on Sheet #5 – this sheet shows slightly different
proportions needed for the finished
Mach 2 bike frame. A narrower frame
means a higher bottom bracket. At
the rear, one is tempted to eliminate the 5 degree bend and just 'do' the frame
straight back to the dropouts. NFG.
Leave that angle in the frame - it's about chain clearance to the rear
cluster. Trust me on this. SHEET
#16 doesn’t exist.
Use Sheet #6 – it just explains the bell formed joint, which is the
same here as in the EZ Clone. SHEET
#17 – The finished bike.
Use Sheets 8, 9, and 10 from the original EZ Clone set to complete the
bike. Heck, use the parts from
the earlier bike! Always,
I suggest a complete assembly and test of the bike before your finish and paint
it. You may want to adjust
that fork, depending on how it handles.
Fork flop is that feeling you notice when a bike seems to ‘fall’ off
center. It seems to actually
lower itself into a turn (actually, it really does lower into the turn).
This is caused by too much trail from that sharp head angle.
Add rake in ¼” or ½” increments.
Test it, see how it feels. Hold
off putting a bridge on your fork until you are happy with this. If
your ride is too wobbly and feels unstable, you may have over-raked your fork.
Start a new one, find a new donor bike if necessary (just for the right
fork, not for starting over). Bend
to 4” of rake, and try that.
I like to try a fork on a bike until I reach a point of satisfactory
handling. THEN I bother to
strip it down and add the brake bridge. There
is a formula and a modest program for predicting geometry of preferred rake and
trail - if you know the head tube angle and the trail, you can calculate the
rake, etc. I hope to add the
reference to this site with the author's permission.
Eventually. But I find
the guidelines mentioned above, plus the careful testing on the road for your
bike, is the best teacher. |
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Send mail to
adcarson@juno.com with
questions or comments about this web site.
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