Mach 3 Script

The Mach 3.

There is a new idea in the development of the Recycled Recumbent, we’ll call it the Mach 3.   It’s really born from the clamor in public – there is a fascination with the idea of the dual 26” wheel long wheelbase recumbent*.   Several manufacturers make a dual 26 bike – Rans makes the excellent Stratus XP and a few racing models in this configuration.   Lightfoot makes the well regarded Ranger, Cycle Genius made the Raven, and so on.    I’ve been asked several times if it were possible to design the Recycled Recumbent with dual 26” wheels.   I played with it about 4 years ago, at the time I didn’t think I could do it – you CAN put a larger wheel on the front of an Mach 1 or a Mach 2, but the resulting bike handles like a cow, it just isn’t acceptable.  

In January of 2012, some friends on www.bentrideronline.com encouraged me to revisit this idea*.   Through that extended discussion on the message board at BROL, I stumbled across a new way to make a bike that DOES allow for a dual 26” wheel  Recycled Recumbent.   More on how to do it in a moment.

I am asked, what is the difference?    How does a Mach 2 differ from a Mach 3 (aside from the obvious)?    Why would you want one bike over the other?    The first answer is personal asthetics – some folks just LIKE the look of the big front wheel more.    Maybe there is a mental ‘rightness’ about 2 wheels the same size – I can’t answer that for you.   But there is no denying a preference like that (if you have it).   It isn’t wrong – if the bike looks ‘right’ to you (any bike), it may ‘be’ right, in the sense that it’s the bike you like to see and be seen on, hence the bike you will ride.    The second answer for a dual 26” wheel bike – always quoted by proponents – you only need to take one size spare tube on the road.   True, 2 wheels the same size makes sense this way, at least until the second flat.  

There is as well a difference in the ride, and that is the key issue.    The Mach 3’s bigger front wheel does smooth out the bumps.    When you get this bike up to cruising speed (anything over 10 mph, depending on the engine) it feels great – a real road limo.   On rough surfaces, over bumps, there is no denying the larger wheel evens things out, makes a cushier ride.    The Mach 3 seems to accelerate easily, maintain speed well.   There are two trade offs for this cruising feel.    Compared to the Mach 2, low speed (AKA uphill speed) handling on the Mach 3 is a little compromised.   Nothing you can’t cope with and learn to handle, but it isn’t quite as nice.   There is a little fork flop.   Two, and this is more practical, the bike is a long sucker.   The change in geometry lengthens the front end for a given rider size, and the larger wheel in front – well, it’s usually at least 8’ of bike, end to end.   So parking, transport, etc. are just a skosh more challenging than for a Mach 2.

Third, for you builders, is ease of construction.    The selection for the front donor bike is more tricky than either the Mach 1 or the Mach 2, the potential pool of acceptable donor bikes is lower.   The Mach 3, like the Mach 2, is a more challenging construction than the Mach 1 – and it is just as unforgiving of your mistakes as is the Mach 2.   

This script for the Mach 3 leans heavily on your experience and my earlier descriptions and drawings of the Mach 1 and Mach 2 bikes.   I won't repeat here the lessons and techniques shared by all three bikes.  The only drawings exclusive to the Mach 3 are the four sheets labeled 23A, 23B, 27A, and 27B, intended to slip in sequence with the other drawings (EG, Sheets 1-8 work for the Mach 1, for a Mach 2, substitute, for example, Sheet 12 IN PLACE of Sheet 2.   For the Mach 3, substitute Sheet 22 in the sequence).    There’s a quiz later on all this substituting.  And all the drawing sheets are available for download here - Files.

HOW TO DO IT

The key to making a Mach 3 is the selection for the front donor frame.    Look for a Mountain Bike frame in your donor choice.   Here are two from my current collection, they look so ugly because they've already been in the oven to bake off the original paint.
Notice on these frames the steep angle of the head tube.   On  ‘normal’ road bike, you will see that the head tube is parallel to the seat tube.   Look for a donor bike where the head tube is like this – relatively steeper than the seat tube.    Straight forward,  aggressive MTB designs are often like this, I can’t predict for you which brands and models.    It won’t come with a dropped handlebar like a road bike, and it won’t come with a heavy shock fork (and certainly not with a pivoting shock mount frame!).     
 
When you cut this frame apart to configure in the method of a Mach 2 (with the flipped head tube, you get a very shallow head tube angle, and as well, you will find the resulting front end is ‘elongated’ , like you see on Sheet 23A.   (Mach 3 Drawings)   See the difference?  I’ve shown an overlay of the Mach 2 and the Mach 3 first assembly.   

This elongated feature for the front end geometry will allow for clearance between the crankset and the larger front wheel.   As you lay this front end out for final cuts, you of course want to check that clearance.   Just as for the Mach 2, lay out the rough cut pieces of the front donor frame, use a fork, use a crank, and check clearances.    IS there room on the up-tube for the front derailleur over the chainrings?  IS there clearance between the pedals and the wheel?    Keeping the front geometry as small as possible is no longer as critical as it is with the Mach 2, but still, keep the frame as narrow as is reasonable.  

 
 
CAUTION – this occurs with select donor frames.   Notice on Sheet 23A, NEED LINK  in the overlay of the Mach 2 and Mach 3 front ends, how different the ‘down tube’ angle is?   This is the tubing that runs from the bottom bracket up under the top tube.    Not every Mach 3 frame, but many of them, will result in this extreme, vertical (almost) downtube.   This is a mechanical problem later, because it alters the angle of the typical clamp-on front derailleur as it works with the crankset.   If you have this in your front assembly, I advise adding a short, mitred and fishmouthed tubing section to mimic the original downtube and angle of the typical road bike frame.   The third picture on Sheet 23A   (Mach 3 Drawings) shows the addition of this small tubing (use 1 1/8” tubing) section.
 

Sizing a frame from this front end is not the same as for the Mach 1 and the Mach 2.   The front assembly is longer – the head tube is farther in front of the bottom bracket, so my ‘normal’ sizing advice no longer applies.   The new reference for how long to make a frame still measures along the top tube, but that measurement is taken from a point perpendicular to the center of the bottom bracket to the rear end of the frame.   Sheet 23B includes my rough chart on finished frame lengths with this new measurement.  (Mach 3 Drawings)

OK, you’ve made the front assembly, you’ve picked and added donor section for completing the top tube, and finished the second assembly.     You can proceed with a rear triangle much the same way as the other two bikes do this.   I suggest looking at larger cross section rear triangles from the MTB’s you used on the front frames – we want this to be a sturdy bike.

You can proceed as well in the same fashion as the earlier models to add the bottom rails to the bike.   You may as well consider a diagonal brace in this frame, a stiff ride is a better ride.

Mach 3 Drawings

Sheet 27A is a comparison drawing, showing first the Mach 1 Frame, then the Mach 2, then the Mach 3 frame.   They are very close cousins, and, of course, all recycled bikes made from other bike frames.   Your frame will certainly vary from the drawing.   No matter what, every bike is different.

 

Two sample frames.   They aren't always as radical as the first one, sometimes, depending on the donor bike, the Mach 3 frames can look almost 'normal'.   And not even need the added downtube.  
 
FRONT FORK – This too is a more carefully selected fork than you might otherwise choose for a Mach 2.   I prefer Unicrown forks for the Mach 3. 
 
On the left is a pretty typical brazed crown fork.  On the right is a unicrown fork, where the curved fork blades are welded directly to the stem. 
The unicrown forks are a little heavier, the weld is arguably sturdier than a brazed-crown fork.    But this fork selection can be a little tricky too – most of the donor bikes with plain unicrown forks use very heavy tubing sections for the fork blades – these are hard to bend.   
Look at these two pictures of Unicrown forks – the one  on the right is pretty typical, the other a little bit ‘higher end’, the fork blades are smaller sections, finely tapered.    If you can find one that looks this nice (burnt paint aside), treasure it.   If not, try to bend the heavier fork – but be prepared to fail.    Sometimes these forks bend in the wrong spot – right up near the crown, rather than down where you intend the raked bend on the fork blade near the dropouts.   I find I do have to cut the brake canti's off to bend the forks properly.
Proceed to rake this fork to about 3.5” – not quite as much rake as a Mach 2 normally gets.   Take the time of course to align this fork carefully – this is always a tricky business.   The same layout grid as for the Mach 2 works for this fork.   This is the way I do it here -
 
 
 
You don’t need an added fork bridge in this Mach 3 fork – there’s one job you don’t have to do!     When I make a Mach 3, though, I prefer to add brake studs to the frame and fork, I like to have great brakes on this bike.   

Sheet 27B is a sketch of the finished Mach 3 bike.  (Mach 3 Drawings)  That’s just my kind of fun.   

That’s the summary of how to do it.   Detailing the frame, painting, assembling a bike are much the same as for the other bikes.   The seat is the same, of course.    This bike will work with the standard handlebar, but it cries out for the more refined feel of the Rans Chopper Bar (modified) that I sell (there are alternatives, as always).   

If you are after the stretch limo, or the look of that great, long bike, this may be your ride!   

*Credit Lisa, a contributor on BROL’s message board, who asked me last January (2012) if I could build something like the Lightfoot Ranger.   That question snowballed into what you see here.
 
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