cbr125r improve efficiency + top speed

[Spaghetti Man]

Greetings from Australia,

Currently I am getting about
94mpg city driving at<34mph
82mpg highway at 70mph.

Top speed on level ground with a tuck position is 70mph (110km). The silly speedometer says 125km per hour at this speed.

Taking a look at the super efficient recumbent motorcycles I am wondering if any gains can be squeezed out of the inefficient design of the cbr125r.

[Grant-53]

Yes, the two things high efficiency motorcycles have in common are lower numerical gear ratios and aerodynamic body work especially behind the rider. There are several threads here and see the Craig Vetter, designer and inventor of the Windjammer fairing,Triumph Hurricane Motorcycle Streamliners and fuel economy motorcycles site for ideas.

[Spaghetti Man]

Thank you for your reply.

I did some reading regarding the vetter rifle. I would like to know what I would need tools+supplies in order to make such a fairing. If I know what I need I'll be able to set up a budget.

Any recommendations for making such a fairing would be helpful as the details are allusive.

[sendler]

The CBR125R is probably the best starting point for a fuel efficiency competition vehicle but don't make any mod more trouble than it is worth. Otherwise you will get started and never finish a huge project like that. Find a comfortable head forward riding position by laying on a big, stuffed, tank bag. Once you find a nice, high position, add a taller windshield that comes up just below your eyes. And then make a plank style luggage system or a simple truncated tail trunk which will be more aero and give you large and locking storage. Then you may be able to go up 1 tooth on the front sprocket.
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I can get 90 mpgUS at 50 mph very easily without much tricky riding on my CBR250R. I got 105 mpgUS at the Vetter challenge and 136 mpgUS using EOC at 45 mph at the Green Grand Prix.
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[Grant-53]

Agreed. The biggest gains are from the tail section. A big issue is putting a foot down and the Rifle fairing doesn't allow that without cutting a hole. See Vetter's Chapter 83 on the latest developments. A bulkhead and skin structure is much easier than a fiberglass body. The shape is the thing.

[Spaghetti Man]

I went down to a local insulation business and

polyurethane costs $40.54 for 75mm x 1200mm x 600mm.
Polystyrene costs $19.80 per 100mm x 1200mm x 600mm.

Polyurethane was recommended because although the upfront costs are higher and the material is not very nice to work with the polyurethane is not destroyed by poly resins. Exoxy resins being more expensive.

I also went down to the local fiberglass supplier and although I got some advice I did not get a unit price per square meter that I wanted. I have found an ebay store that offers products at reasonable prices.

Considering that 10,000km of petrol costs about $300 the budget will not be very high. With such a low budget it is going to be difficult to figure this out.

The biggest problems to solve will me.

1) Designing an optimal fairing.
2) Transferring that design to a fiberglass mold material.
3) Once surface area is calculated and supplies ordered making the fiberglass fairing should not be impossible.
4) Sanding and painting without it costing $1000.

[sendler]

Ben has made a couple fairings, Check out his threads so you know what you are getting in to.
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http://ecomodder.com/forum/380452-post120.html
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[bschloop]

Thanks for the plug.
If you plan on removing the foam when you are finished laying up your glass you can just st use polystyrene, and wrap it in a layer of tin foil to protect and release your plug. If you want to use a foam sandwich lamination, I would recommend splurging on the epoxy, and using extruded polystyrene unless you can get the polyurethane that's used in surfboards. You could also laminate the outside with polyester resin over a foil wrapped plug, then add in foam ribs afterward using epoxy. Hope this helps.

BTW, I am planning on making my next fairing set available for purchase as soon as I've finished with developement. As it's designed around the CBR250 it should fit your 125 fine.

[Grant-53]

If the fiberglass method is too expensive or time consuming for just one unit, consider a space frame and skin construction.

[Spaghetti Man]

I ran my bike into a telegraph pole, just got out of hospital with broken leg. I now have an even better reason to make new fairings as the old ones got a bit stratched up. Will need to heal up before I go ahead with the plan.