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Author Topic: Iceliner-Speed Weekend inSweden  (Read 6450 times)

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Offline Polyhead

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Re: Iceliner-Speed Weekend inSweden
« Reply #15 on: March 17, 2016, 06:41:34 AM »

I'm Bjorn from Sweden. I have participated in the Speed Weekend on ice here in Sweden a couple of times. My last attempt was last weekend with my 125 cc Iceliner.
The goal is to join the 200 kph (124 MPH) on ice club with a 125  cc bike.

I have serious problem with bike stability. The bike tends to follow any track on the ice. I have tested with several fork angles and also trails. It would be nice with some input from experienced LSR bike builders.

Some facts about my bike:
- Engine and rear end from a 1991 Yamaha YZ125 MX bike.
- Front end from a mini MX bike
- Approx 18” welded steel tube frame extender between front and rear end. Bolted to rear end. 
- Rear wheel 19"
- Front wheel 14"
- Wheel base 1900 mm (75")
- Weight with driver approx. 190 kg (420 lbs)
- Weight distribution front/rear 48/52
- Variable fork angle 25-38 degrees
- Variable trail approx. 75-125 mm. (3-5") Works best (less bad) at approx. 100 mm trail.
- Seat height approx. 625 mm (25")
- Rear suspension, tested with both original MX damping and also with stiff (iron bar)
- The frame has some sideways flex. When I shake the bike from side to side holding in the handle bars I can feel some flex but not that much.

The bike is more or less undrivable. It is very unstable and extremely track sensitive regardless of speed.
Are the chassis parameters totally wrong?

Any input and ideas are very welcome.

Regards Bjorn

(Please note than english is not my native language and my use of word might be incorrect)

Little front wheel and big rear wheel = wobbly goblin.  That's why most cruiser are set up exactly the opposite, with a larger diameter front wheel and a smaller diameter rear wheel.  This has to do with the differening arcs the wheels travel in when in a turn.
Ben 'Polyhead' Smith

Offline Polyhead

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Re: Iceliner-Speed Weekend inSweden
« Reply #16 on: March 17, 2016, 06:43:10 AM »
Hmmm...I for one, would be gripping those bars very tightly............ :cheers:

And you'll be inducing head wobble when you do.
Ben 'Polyhead' Smith

Offline kawabjorn

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  • Location: Sweden
Re: Iceliner-Speed Weekend inSweden
« Reply #17 on: February 28, 2017, 02:43:03 PM »

Speed weekend on ice 2017 is done.
This year I changed to snowmobile front end, lower "rolling resistance" with skis compared to a front nail tire. Also better stability with 3 points of support compared to two on a motorcycle.

Unfortuneatly I only was able to make one run due to engine problems. The speed was low, just about 100 kph on my own GPS but the chassis performed well and the stability was OK.

Next year I´ll try to build some fairing for lower air resistance.

BR Björn

Offline Koncretekid

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Re: Iceliner-Speed Weekend inSweden
« Reply #18 on: March 01, 2017, 10:28:36 AM »
100 kph recliner - - looks like fun and at the end of the day you can take a nap!
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!