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Topic: feet forward bikes  (Read 619 times)

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bobwalton
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« on: January 05, 2021, 01:46:39 pm »

Does anyone know where I can get some nice enclosed bodywork for this bike I made

https://youtu.be/ECzFlrXNry8
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« Reply #1 on: January 05, 2021, 01:51:25 pm »

.......Something like this maybe:-
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kver
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« Reply #2 on: January 05, 2021, 03:02:26 pm »


Does anyone know where I can get some nice enclosed bodywork for this bike I made

https://youtu.be/ECzFlrXNry8


That definitely wins some cool points!!!  why hide it behind bodywork???  Smile

What's the wheelbase?  how is it for slow speed handling?  I assume its actually very stable at speed with the longer wheelbase, lower CG, and negative rake.  It probably has much better bump compliance too... but I bet you'll get a tendency for the front wheel to want to tuck and fight when braking downhill into a turn...      
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« Reply #3 on: January 05, 2021, 04:14:20 pm »

I don't know if you've noticed, but on a normal bike, if you sit on it at stand still and turn the handlebars left and right, you might just see the head stock going slightly up and down. When its lowest, the steering is at full lock. So gravity pulls (flops) the steering to one side. On this bike, because the rake is reversed, gravity straightens the steering. So, especially at low speed, it helps keep the steering in the direction of travel. I think at low speed, it's the rider that does the balancing, so the steering gets a bit heavy. I don't know if its just me, but on a hairpin corner, on a normal bike I never go so fast I can get my knee down. But I can when I'm going faster. I think this is due to this wheel flop effect. You don't get that on my mini bike. In other words, yes, at low speed it turns excellently. I hoped you could see that on the video. It's much more stable than a bike that size should be because of the steering. You might think that low speed cornering isn't important, but if you are racing around a hairpin bend, the first guy around the tight corner is the first on the gas, and so will go faster all the way down the next straight.
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« Reply #4 on: January 05, 2021, 04:29:18 pm »

I forgot to say the front brake has anti-dive. There is a lever that stops the brake caliper going round with the wheel, which also pushes up slightly on the front of the bike when the brake is used. That cancels out the dive but lets the suspension work normally, so the front doesn't tuck under on the brakes. https://i.pinimg.com/originals/c4/96/be/c496be4a48ef0e8b5d35fb91788c01be.jpg
« Last Edit: January 05, 2021, 04:41:07 pm by bobwalton » Logged
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« Reply #5 on: January 05, 2021, 05:02:36 pm »

Good job. You an engineer?
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« Reply #6 on: January 05, 2021, 05:09:30 pm »

nobody's perfect  
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« Reply #7 on: January 05, 2021, 05:55:48 pm »

Nice thread  Thumbsup
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« Reply #8 on: January 07, 2021, 05:58:12 pm »


I forgot to say the front brake has anti-dive. There is a lever that stops the brake caliper going round with the wheel, which also pushes up slightly on the front of the bike when the brake is used. That cancels out the dive but lets the suspension work normally, so the front doesn't tuck under on the brakes. https://i.pinimg.com/originals/c4/96/be/c496be4a48ef0e8b5d35fb91788c01be.jpg


Awesome again ---  I was actually assuming the suspension would lengthen under braking as the wheel stops but the bike still pushes forwards (bad explanation I know) --  and that would counteract the weight shift forwards -- the suspension kinematics could be tuned to balance those forces out.   Similar to the high-pivot mountain bikes that are coming out now....  It's a good thing to keep the rider and engine (CoG) low on your design though --  I imagine a stoppie would not be so cool???    

Still way impressed with the of the box thinking ....    Thumbsup
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bobwalton
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« Reply #9 on: January 08, 2021, 03:52:59 pm »

I'm afraid stoppies are out on this thing. It's got linked brakes anyway with a roughly 50-50 spread. The steering I have used here allows you to ride at roughly the same height and the same sitting position as you do in a family car. I know this particular bike is tiny, but with the right resorces you could put this type of steering on a normal sized bike. Then you can put a bullet shaped fairing on it and the drag would be tiny. Even without a fairing, my bike should have 2/3 of the drag of a normal bike because, with the rider on board, it has 2/3 the area looking from the front. That's just because it is 2/3 the height. If you compare it with the nearest equivalent 'normal' bike, say a Honda 125 (mine is 140cc) a Honda might weigh 130kg, compared with my 80kg. So my garden shed effort has got 2/3 drag and 2/3 the weight of Honda's best effort. Scale it up to 'full size' put an electric motor in it if you want, and it will easily out-perform the competition. Remember, I just made this thing myself, and without access to trick materials or fancy technology. In terms of drag and weight, it's way better then anything comparable - even Honda's best effort. 

Oh yeah, you could make it look less ugly with a nice, sleak fairing too. So if anyone knows where I can get one, let me know.  Smile
« Last Edit: January 08, 2021, 03:58:24 pm by bobwalton » Logged
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« Reply #10 on: January 08, 2021, 04:23:57 pm »


I'm afraid stoppies are out on this thing. It's got linked brakes anyway with a roughly 50-50 spread. The steering I have used here allows you to ride at roughly the same height and the same sitting position as you do in a family car. I know this particular bike is tiny, but with the right resorces you could put this type of steering on a normal sized bike. Then you can put a bullet shaped fairing on it and the drag would be tiny. Even without a fairing, my bike should have 2/3 of the drag of a normal bike because, with the rider on board, it has 2/3 the area looking from the front. That's just because it is 2/3 the height. If you compare it with the nearest equivalent 'normal' bike, say a Honda 125 (mine is 140cc) a Honda might weigh 130kg, compared with my 80kg. So my garden shed effort has got 2/3 drag and 2/3 the weight of Honda's best effort. Scale it up to 'full size' put an electric motor in it if you want, and it will easily out-perform the competition. Remember, I just made this thing myself, and without access to trick materials or fancy technology. In terms of drag and weight, it's way better then anything comparable - even Honda's best effort. 

Oh yeah, you could make it look less ugly with a nice, sleak fairing too. So if anyone knows where I can get one, let me know.  Smile


With your obvious skills and ingenuity -- you could just make a fairing.   Fiberglass is easy to work with -- foam makes easy molds - just have to wrap with saran wrap if you use polyester or vinylester resins and styrofoam)... or carve wood molds and slather with mold release  --- and lay-up some gelcoat  -- some 300g chopped strand mat (csm) and then 3 layers or 6 oz cloth (or 2 layers of 9 oz)  another layer of csm and you're good.   After everything is dry and solid -- demold -- add reinforcing strips and tabs to connect to the frame on the inside as needed and sand and paint the outside...  

Resin is cheap --- glass cloth is a bit more expensive --  but fiberglass will be much easier to work with than the awesome metal work you've already done...  

Personally -- I like the engineering and would rather see it than have it behind a fairing...  Or maybe a partial fairing -- a long dress with a slit is a lot sexier than shorts that show eveything or a maxi-dress that covers everything...  
« Last Edit: January 08, 2021, 04:27:42 pm by kver » Logged
bobwalton
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« Reply #11 on: January 09, 2021, 03:42:40 pm »

I don't know how to create a nice elipsoid body shape in the first place, without asymmetry and lumps and bumps. It has the potential to look seriously bad. Crazy Btw, thanks generally for the comments on this forum. I sometimes get unhelpful comments from people that don't 'get' what I was trying to do.   Thumbsup
« Last Edit: January 10, 2021, 09:10:32 am by bobwalton » Logged
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