North Pole Motor 1/4

The base will be a frame and engine from a 2001 Yamaha YZF-R1. Many of the parts placed around it will be anything but standard. Still, I will try to keep the R1 look as much as possible.

Below is an overview of the most important changes and the reasons why.

The widest tyres which fit between the front legs and the swingarm of an R1 -even if they have a much larger diameter than the original ones, which make them roll a lot easier over obstacles and give them more carrying surface- turned out not to bring sufficient carrying capacity on sections of the polar ice with less compact snow. Especially the rear wheel sank in it and in most of those occasions it only found enough grip after the studs got to the polar ice surface.

• I’m searching for tyres which have a little bit bulging tread over the width.
• The rear tyre should be approximately 60 cm wide. For the front around 40 cm will be sufficient.
• The tyres are preferably developed for vehicles that ride in snow or mud.
• The more pliable the tyres are the better it is, because in combination with reducing the pressure, it brings you the best grip and especially more carrying capacity.
• In contrast with the wish to have pliable tyres stands the fact that the tyres will need to have several ply because the ice ridges can be razor-sharp. That became clear to me after I heard what happens with 4-wheel-drive cars that set out on the polar ice around Barrow. Regularly they blew a tyre to pieces, especially when their speed was high.
• The tyres must be suitable to use in temperatures around -40°C.
• The existing profile is of less importance, as there can be put on a suitable tread.

During the last two winter challenges I used BestGrip studs. I experienced that they improved the grip and the (road)holding enormously. They made such a difference that I am going to use them again, for sure. The fact that Bestgrip studs don’t wear quickly on asphalt is of less importance this time.

After I know which tyres there will be used, rims can be made. This could be existing rims which are suitable for the tyres, in which an R1 hub will be mounted. Or they could be milled out of one piece.
If there is a company out there willing to do this for me, please inform me!
The wheels will be stopped by standard R1 brake rotors, callipers and pads.

Having a much bigger and wider rear tyre, means that a standard chain drive won’t be usable anymore. In search for the best solution I balanced out the pros and cons from three different options. Electric, hydraulic and the regular drive with two extra sprockets on an axle in between. I opted for the latter.
Read why.
• Electric
When using this option, the bike’s crankshaft would power an aggregate, which delivers the necessary current for an electro engine that would be mounted on the rear wheel.

Pros:
+ By mounting an electro engine on the front wheel, too, you get 2-wheel drive. This increases the grip and pulling power.
+ The current can also be used to power the electric heated clothing and to charge the extra starting battery and batteries for cameras and suchlike.

Cons:
– Where to place the aggregate? In the space where the transmission is fitted?
– Aren’t we going to lose too much horsepower this way? To find out we need lots of time and even then, we are not sure if this is a real option!
– I expect that electronics are more sensitive to interference than when using the existing concept, in which the speed is regulated via the right-hand and a gearbox.
• Hydraulic
In this case the bike’s crankshaft -or the axle that holds the front sprocket- would drive a hydro pump. The produced oil flow would run via a pipe to a hydro pump, that would be mounted on the rear wheel.

Pro:
+ Building a 2-wheel drive is possible.

Cons:
– Where to place the pump?
– The time-consuming search to find out if the loss of horsepower is acceptable.
• Chain and sprockets with an axle in between.
When going for this option, the bike’s front sprocket brings the power over to the axle which will be placed in front of the rear wheel, using a short chain. Parallel to the power receiving sprocket, there will be a sprocket which passes the power on to the rear wheel. Depending on the width of the rear tyre -and by that the position of the rear sprocket- the distance between the two sprockets on the axle that sits in between could be as much as 15 to 20 cm.

Pros:
+ Little fuss, which makes it easier -and therefore quicker and cheaper- to build.
+ Little can go wrong, because there is not much that can fail or break.
+ By juggling with the size of the sprockets that sit on the axle in between, I can reduce the speed from the North Pole Bike like I desire, without having to use a huge and heavy rear sprocket.