Project chopper

Joined
Dec 29, 2016
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255
Location
Lanc's, England
For a long time now I have slowly started to build a chopper.
This is the inspiration for the bike.


My rear and bottom frame will be made from dual 5/8" x 1/16" tube and the fork and the rest of the fram is 1" tube.
I'm a bit worried that the frame and fork will be flimsy, but I'm going for it, you can always rebuild if it fails.
The tyre is fat frank 26" x 2.35" on 65mm wide rims.


The rear hub is a shimano with 8 internal gears and coaster brake. My first design was to use the coaster brake only and no front brake for a clean look.
But i've changed my design and decided to go electric with a hub motor in the front wheel so I will add a disc to the front and mayby the rear as well.
I wanted the dual tube at the bottom of the frame so a battery pack can be mounted parallel with the ground inside the frame.
The motor controller will be hidden inside the bracing plates behind the head tube and the motor will be controlled with a bottom bracket torque sensor.
 
Joined
Feb 7, 2008
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2,682
Location
Nottinghamshire England
Hi there

If you want to be legal on the road you will need two brakes operated by independent systems , although they can both be on the same wheel !

that guy is also famous for his forkless bikes ? Olli's bikes



and more..



regards Paul
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
.....have used those Fat Frank tyres over here and in the UK. They really have the 'look', but no other tyre I've owned has been so prone to punctures. Those choppers look like great fun to build and ride - good luck with it all...........
For £13 a tyre, I can live with a few punctures.
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
Hi there

If you want to be legal on the road you will need two brakes operated by independent systems , although they can both be on the same wheel !

A chopper road legal? whats the fun in that.

The picture above is the same bike as my inspiration. I didn't know he used fat frank tyres.
 

graucho

Super Moderator
Joined
Apr 21, 2009
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1,855
Location
Minnesota, Twin Cities
I love that style and look. You can always add a sleek looking cross member or gussets to the frame for extra support without compromising the look. Looks like a fun project, and ride.


For a long time now I have slowly started to build a chopper.
This is the inspiration for the bike.


My rear and bottom frame will be made from dual 5/8" x 1/16" tube and the fork and the rest of the fram is 1" tube.
I'm a bit worried that the frame and fork will be flimsy, but I'm going for it, you can always rebuild if it fails.
The tyre is fat frank 26" x 2.35" on 65mm wide rims.


The rear hub is a shimano with 8 internal gears and coaster brake. My first design was to use the coaster brake only and no front brake for a clean look.
But i've changed my design and decided to go electric with a hub motor in the front wheel so I will add a disc to the front and mayby the rear as well.
I wanted the dual tube at the bottom of the frame so a battery pack can be mounted parallel with the ground inside the frame.
The motor controller will be hidden inside the bracing plates behind the head tube and the motor will be controlled with a bottom bracket torque sensor.
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
The rear and lower frame is first on my list.
I will make 2 U-bent pieces to go around the rear wheel, so I need a jig to bend around.
I'm using a plumbing torch with map-x gas to heat sandfilled tubes so I can bend them.
The rear wheel is 135mm over the hub so after some calculation and cutting into some scrap 1" square i got this.


135mm but on the inside, ops. so after some more bending grinding and welding it look like this



Now it's 135mm on the outside.
I will use the same jig for most bends so I started with the 2 lower pieces from rear wheel to head tube.
Only needed a 59 deg bend.
The first bend wasn't to god, but the second was better.
I will later set up the frame in a jig and then I will decide if the first bend is OK or not.



Next the 2 U-pieces
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
After capping and filling a meter of 5/8 x 1/16" tube I started the rear U-bends.
My first thought was to bend half then turn around and bend the second half.
But Instead I did the hole bend in one go.



They are not perfect and there is a slight difference between start and end point.


But I think I can get away with it.
The next bend is the tubes between top and bottom rear frame.
I will not use heat this time only sand fill tube and brut force.
I will try around a old rim first, to find out how much the bend springs back.
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
Todays task was to bend 2 pieces of 5/8 tube in a nice arc to follow the tire arc from bottom frame to top frame,
I only need about 2 x 400mm of arced tube.
I sandfilled and caped the ends of a 1800mm lenght of tube and fastened a 26" rim to my workbench as a guide.
I cold bended the tube around the rim and was supriced how easy it was and how smooth the arc become.
Slightly to tight, but that was easily corrected.


I made 2 arces on the same lenght of tube, so I will cut it in 2 pieces, and if needed fill with sand again for a final adjustment.
 
Joined
Sep 12, 2012
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2,869
Location
Apple Valley, California, USA
After capping and filling a meter of 5/8 x 1/16" tube I started the rear U-bends.
My first thought was to bend half then turn around and bend the second half.
But Instead I did the hole bend in one go.



They are not perfect and there is a slight difference between start and end point.


But I think I can get away with it.
The next bend is the tubes between top and bottom rear frame.
I will not use heat this time only sand fill tube and brut force.
I will try around a old rim first, to find out how much the bend springs back.
Nice job

Want to know more.....

Did you use clean sand, or yard/dirt sand ?
How did you attach the end caps ? (weld on? )
How much heat do you think it required?

Just warm/hot ?
Really Hot...Red glow ?
 
Last edited:
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
Hi Ed

From the beginning I bought some kiln dried sand, which is the best to use.
Last year i dried some ordinary building sand in the oven to bend some pvc plumbing pipes and this time
I used some of that to, a bit coarser than the kiln dried sand but works as good.
The important is that the sand has to be dry otherwise the tube can explode when heated.
I weld a piece 1.6 mm sheet over the the ends, trying to leave a small gap in one side as a pressure relive valve and of coarse the sand is packed as hard as I can.
For heating source I using a Rothenberg plumbers soldering torch with mapp gas.
I let the tube get as red as possible before a slowly bend and move the heat forward.
The U bend took about 15min to complete, so you are using a lot of gas.
This time a tried a cheaper alternative to mapp gas called map-x but it changed the flame and the performance of the burner to
the worse so never again.
Up to 25mm tube works ok this way, I have a project in my head where I need to bend some 40mm tube, I did it with difficulty
on the python, but next time I will borrow my sons soldering torch and use 2 burners simultaneous.
I will later on in this project try to braze some fittings on using the solder torch and silicon bronze filler rods.
I have tried it before with mixed results.
 
Joined
Sep 12, 2012
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2,869
Location
Apple Valley, California, USA
Thanks for the great explanation.

Especially about the 'must be dry' part, and keeping a 'pressure relief'.

I first learned of the sand filled tubes from my father, back in the 60's.
He worked for a tube bending company, in the San Francisco area.
They made many of the tubes that are used on some roller coaster rides.

I tried using the sand filled method while building my PVC car. I guess I didn't have the right sand, or method, as I didn't have good results.
I learned how to bend the PVC with just a jig and heat gun. All the exhaust pipes on my StreetRunner build, were hand bent in that manner.

I would think the 'cold bend' method for metal, would work as well for smaller diameter tubing. Interested to know how it worked for you.
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
To make it hard for myself, I will add a electric hub to the bike.
I bought a front wheel hub motor, bb torque sensor, brake handles and thumb throttle.





I know I'm missing speed sensor and PAS sensor, but I will order again this week buying the battery pack and all other bits I need.
The PAS sensors BMS battery sells have 12 , 10, 8 or 5 signals. I can't find any reference in the manual. So which shall I choose? Link to the manuals https://bmsbattery.com/index.php?controller=attachment&id_attachment=4 and
https://bmsbattery.com/index.php?controller=attachment&id_attachment=5
The cable supplied with the hub to connnect to the controller was to short, so I also need to order a longer one.
I got the BB torch sensor because it gives a 5v signal when you back peddling, so that could be used to disconnect the motor
when you use the coaster brake and I think this kit also has regenaritive braking which might be a good combo to the coaster brake.



The information I have about the products are very limited, only how to program the controller and the only reference to back pedling I found so far is a "reverse power sensor signal"? Do the motor automatic disconnect when you back pedlar? Or do I need to cut the cable, find the reverse signal cable, so it will switch a external relay or go direct to one of the brake input connectors?
I need some help.
 
Joined
Dec 29, 2016
Messages
255
Location
Lanc's, England
I forgot to mention that I will proberly not use the thumb throttle, my thought is to only control the bike by the pedals.
My goal is to have the minimum input possible to control the motor. So is there any sencors I don't need, let me know.
 
Joined
Dec 29, 2016
Messages
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Location
Lanc's, England
Over the last 3 month the progress has been very slow.
A few of the brackets and most of the bits for the fork has been made .
But today I was able to make my first mock-up.



The bent piece of tube around the wheel will be cut to fit between the 2 arched tubes.
The length of the bike surprised me, I knew the drawing said over 2.8m, but didn't realise how long 2.8m was.
I'm still working on a way to fitt a seat.
My latest design is to shorten the top tube, which is 25mm, and splice it with a short piece of 22mm tube nearest the rear wheel,
I can then mount a standard seat bracket on the 22 mm part of the tube.
 
Joined
Sep 12, 2012
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2,869
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Apple Valley, California, USA
I'm a fan of choppers. It does look quite long.

Not to worry about the length of time.
After all, the Inferno was started Mar 2013, and it's not finished yet.

I'll be watching your progress.
 
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