Project chopper

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Dec 29, 2016
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Welded the fork together today and brought the bike out to see if it's strait.



Seems ok, but it's very flimsy, because most welds are only tacks.

 
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Dec 29, 2016
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Most of the welds got more tacks on today and a temporary seat and handle bars was added, so for the first time I put weight on the frame.
The frame seems rigid enough, but there is some flex in the fork.
When I sit on the seat the top of the fork drops about 10-20mm, it would give a comfortable bounce when you ride, but what would happen if you hit a pothole?
I knew that my material choice was on the weaker side, that was one reason I decided to design the under fork hold down from the head tube.



How much flex is allowed in the fork?
The remedy is to cut the fork in half and insert a 0.5m or so of 22mm tube and weld it all up again, but then you add more weight. Hmmm...
The bike as the pics but with temp. handle bar and seat weighs just under 20kg, so finished with battery, between 30-35kg? I'm pleased with that.
 
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Are you certain it's the forks that flex or is it the main chassis or a bit of both? It's hard to see the lower fork mount but it looks fairly flimsy with scope to give.
 
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here is probably some flex in both, but mostly in the fork, if you bounce the front wheel you can notice a bend which springs back immediately.
The fork tubes are 25 x 1.6mm tubes which I thought from the beginning could be a problem.
I bent a sheet of 5mm steel into the lower fork holder and that is strong enough and also reaches lower down the forks than a normal brazing.



The flex in the fork starts under the lower support.
I have a 2m length of 22mm tube, I need about 1m for the handlebars and risers, so about 1 m is over.
One way to strengthen the fork is to cut the 22mm tube into about 15cm lengths and push them down the tube and leave 5cm or so between each piece, to keep the weight down and spread the support, the pieces will be welded from the outside through drill holes, just a thought.
I think I will continue with the build and face the problem later. But I do rather like the bounce.
 
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Given that info it does sound like you need some support down there. I'd expect a permanent curve to set in before long without it. It seems like a good place to make a composite. ie reinforce with ally or carbon tube rather than steel and glue it in. You'd get some of the give of the steel with some of the rigidity of ally or carbon, not unlike adding rebar to concrete to get a product superior to either on it's own.
 
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Because of the length you keep that flex. You can ad a second one next to it, that helps and you don't need to do it over the complete length.
Inside works also, but one next to it ad a small distance, works better.
 
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Great build , get it on the road ! you may be ok , mine looked very similar and rode fine for years :-



I liked the bounce brought a smile t my face watching it , It was so much that over time the weight of the cable nipple on the front brake cable fatigued and snapped the cable at the clamp however forks were ok.



Maybe it is the other end you need to worry about :whistle:

Paul
 
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Thanks popshot, emil and stormbird.
Went to bed with a brain storm and this morning my solution is to add a "downtube" from the seating area to the bottom bracket,
It will stabilise the frame and also simplify the fixing of the bottom brackets tube. Then to finish the build and if a problem with the bounce, replace the fork legs with new tube, with a 2 or 2.6mm wall.
 
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I'd imagine there's plenty of spring in any forks that length anyway.
True enough. A stylish girder front fork would fix the problem.

 
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Dec 29, 2016
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Lanc's, England
there's a chain , so I assume it has been ridden ?
Yep, Saturday evening.
For the first 20m I was a danger to parked cars, then I got the hang of it.
The chain needs to be shorten with a couple of links and thanks Paul, because of your comments about Danny's chain links, I did a in-depth research (you-tube) in the matter, and pressed the 2 chains together and only used one split chain link. I'm tempted to press the last link together as well, the chain runs free of the frame and
can easily be removed in one piece.
Next, fit the gear changer, and another short test ride.
 
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Pegasus
They are an interesting ride , the steering is stable with normal centring for about 1" either side of ' dead ahead ' then the flop takes over with a vengeance and it will ' tank slap ' with the best of them.

One hint try and remain upright in the turns stops the front wheel trying to dig in on the corners , worst I think if you have a small front wheel mine was 20" ?

Lots and lots of people rode mine , no one came a cropper and all get the hang of it fairly quickly.

My party piece was to ride off one handed vigorously waving with the other , don't try it in public till you have practiced it :giggle:



Paul

ps this was going in my second chopper .....



I still have it ;)
 
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Dec 29, 2016
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My progress is slow but steady.
A project I wanted finished in spring 2019, is far from finished.
Here is a update:


I mounted two bends to the bottom bracket to finish of the frame. It slow progress because all the cables will be routed through the frame.
The black cable taped to the frame will go through a hole behind the torque sensor and up to the controller



mounted below the head tube and the e-bike display is mounted above the controller, the buttons for the display is hidden in the gusset. When it's finished, all the cables from the controller will also be hidden in the gusset.



So the rear frame is now finished, just need to tidy up a lot of welds.
The bike is wobbly on take of, I presume that's the trait of a chopper, but ones you get going its fine.
My next move is to wire up the motor to see if it's makes the ride worse or better.
My first E-bike so if anybody know what minimum cables (sensors) are needed for my setup, let me know.
 
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Looking good. It's so important on a chopper to keep the lines looking simple. Hiding away as much cabling as possible is a great idea that will add considerably to the look.

Motors generally use interuptor switches on the brakes to kill the motor. You can do without but then will have to suffer the run on. The motor will run for a good half second after you stop pedalling or close a throttle. You shouldn't have a throttle anyway if you want to be road legal. No throttle will look cleaner too on the aesthetics front. If it were mine I'd skip the switched brake levers and just have PAS to keep matters as simple as possible with the least number of wires. PAS sensors generally mount under the BB locking ring and employ a plasic disc with magnets in that slips on the BB spindle before the crank bolts on.
 
Joined
Dec 29, 2016
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Lanc's, England
I bought a bottom bracket with built in torque sensor, so that would eliminate any extra sensors.
The motor is controlled by the torque sensor only and will not run before I pedal, so I presume that the motor disengage as soon as I stop pedal.
It also gives a signal if I pedal in reverse but I don't know the function of that yet. The gear hub in the rear wheel has a built in coaster brake, so maybe
if my system have regenerated braking and combined with the coaster brake that gives me enough stopping power.
I have a disc up front but wonder how safe it would be to use it? The early Hells Angels rode with rear brake only, so why not.
But first I will start on the electric, I presume a 4mm cables is large enough to go from the battery to the controller?
 
Joined
Dec 29, 2016
Messages
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Lanc's, England
Got the electric sorted. Didn't work at first. All cable as they should be, but nothing. There was one, two cable, connection not in the manufacturers
schematic. My suspicion was that it was for a on/off switch, so I put some mig wire across it, and it worked.



I do like the torque sensor, it makes you want to get up in speed, the motor disconnect when you back peddle.
And I get slowly get used to the wobble, managed to do a 180, about 5m turn circle, with my feet still on the peddle. It's much easier than learning to ride my python, but I still need a few more days practice. The wobble happens when I try to change gear, have to let go by one hand and reach down for the gear controller.



It's set a bit to low. I tried to get the rubber of but was frighten to brake the controller, any one knows how?,
so I can make and add a stick shifter.
 
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