介绍: How to Create a Downhill Ski-Bike 2.0
My first attempt at creating a downhill ski-bike resulted in a fully functioning prototype and was overall, a success. It performed as I suspected it would. The ride blended attributes of skiing, snowboarding and biking to great effect. You can find a link to my first iteration here:How to Create a Downhill Ski-bike
Despite the first ski-bike's admiral performance, test riding it revealed there were opportunities for improvement so I developed several design specifications and characteristics that would improve the ski-bike's durability, performance and ease of use. This Instructable chronicles the design improvements and changes that I made to create my second downhill ski-bike. Each step focuses on a specific attribute that I improved.
To avoid creating confusion, from this point forward I will refer to the first ski-bike as Ski-bike 1.0 and the ski-bike created in this article as Ski-bike 2.0.
Step 1: Bike Frame
After a few of my friends rode Ski-bike 1.0, it was apparent that the size of the bicycle frame was too large for most riders. The extra large frame was heavier than the riders were used to and more difficult to maneuver. The shock on the bike frame was also designed for larger riders so smaller riders were not able to fully utilize all of the shock absorbing advantages.
For these reasons, I chose to use a small sized mountain bike frame for Ski-bike 2.0. This would allow smaller riders to be more comfortable with the points of contact, and larger riders to ride the bike with few, if any, trade-offs.
There were two features of the bike frame from Ski-bike 1.0 that I wanted to keep the same. The first was to utilize a suspension driven frame and the second was to have an aluminum frame for it's excellent strength to weight ratio.
For Ski-bike 1.0, I lowered the axle height from the typical 13 inches for a mountain bike to 11 inches in order to lower the center of gravity and improve handling. The modification was effective so I expanded on that strategy for Ski-bike 2.0 by designing the axle height to be 9 inches.
Building the mounting bracket was a five step process:
Weld the pieces together.
Drill holes in the angle iron to line up with the ski binding screw holes.
创建一个基本的枢纽和轴系统,我用圣andard 3/8 inch threaded rod as the axle and purchased plastic bushings (from the retailerIgus) to provide a low friction barrier between the axle and the outer steel sleeve. The internal diameter of the bushing was chosen to match the axle and the internal diameter of the outer steel sleeve was chosen to match the outer diameter of the bushing. This resulted in a free rotating axle with very little unwanted play. I also added lock nuts to the front and rear axles to control the longitudinal pressure exerted on the hub delivered by tightening the outer bolts over the dropouts.
Step 3: Ski Type
As I demonstrated with Ski-bike 1.0, a set of downhill skis cut down in size did work to build a functioning ski-bike, but there were some serious drawbacks. Since I shortened the ski length, I couldn't use the ski binding screw holes so I had to drill long wood screws up through the bottom of the ski to attach the mounting bracket. This method was not secure enough for extreme or long-term use. Another drawback was that the ski could break open or separate on the cut steel edge, ruining its performance, and becoming a safety risk.
The width of the skis was also a factor to consider. Despite being similar in width, I could immediately tell a difference in the performance of my chopped downhill skis on Ski-bike 1.0 and my slightly wider ski blades on Ski-bike 2.0. The extra width increases the amount of leaning needed to catch the ski's edge and carve through the snow. One is not necessarily better than the other; it comes down to the rider's preference.
Step 4: Fork Travel
叉旅行- The amount the suspension fork can compress. The larger the amount of suspension travel, the longer the fork is.
头管角度- The angle the center line of the head tube makes with the horizontal plane. A steeper head tube angle will steer a bike more quickly whereas a slacker head tube angle makes it easier for a bike to travel in a straight line. Head tube angles range from about 66 degrees (downhill mountain bikes) to 74 degrees (race orientated road bikes).
The amount of fork travel paired with the height of the front and rear axles (based on the mounting bracket dimensions) determines the head tube angle. This in turn affects the steering and handling of a ski-bike. Since every bike frame comes in several sizes and has a different geometry, I can't say that there is a single, optimal amount of fork travel for all ski-bikes. It comes down to personal preference of the rider and the terrain.
I really liked the footing setup I used for Ski-bike 1.0 because it provided the familiar feeling of using standard bicycle cranks and pedals and allowed me to change the position of my feet depending on the situation. There were a few drawbacks to this setup though. Without the resistance from the chain and rear wheel, the cranks spun freely, which as a cyclist, I wasn't used to. Another drawback was that the drive side crank arm still contained chain rings. During a crash, the teeth of the chain rings could potentially injure a rider.
Step 6: Ski Rotation Control
Unlike a bicycle wheel that's ready to contact the ground anywhere in its rotation, it's imperative to always keep the skis on a ski-bike with the bottom sides down. Ski-bike 1.0 had no system in place to keep the skis from over rotating in either direction. This potential problem was controlled by limiting Ski-bike 1.0's use to stable snow conditions and no large jumps.
One key attribute of these two systems is that they both can easily be disengaged when needed, such as during transportation.
Step 8: Conclusion
Here is a quick summary of each improvement made to build Ski-bike 2.0 and the resulting performance increase:
- Building mounting brackets out of steel = noticeable increase in rigidity and ability to fasten to ski via screw holes
- Using twin tipped ski blades = allowed sliding backwards and the use of the screw holes for secure fastening to mounting brackets
- Increasing fork travel reduced the head tube angle = more confident steering and control when pointed downhill
- Using short unicycle crank arms = increased ground clearance, no chain rings to worry about, and minimized feeling of no resistance
- Creating a bungee and torsion spring rotation control = prevented front and rear skis from nose diving while airborne
Ski-bike 2.0是一个重大的成功。它实现了y performance goal that I set and more importantly, it was an absolute thrill to ride. While I will ride Ski-bike 2.0 as is for a while, I can't help but contemplate ideas for Ski-bike 3.0. Be on the look out. But until then, check out the video highlights ofSki-bike 2.0 in action!
First Prize in the
Guerilla Design Contest
1 year ago on介绍
Reply 3 years ago
I don't think there's a real risk of hitting the bottom bracket. Even with the axles lowered, the suspension on most mountain bikes doesn't have enough travel for the bottom bracket to drop low enough to hit the ground. Another aspect is that I'm only using this on ski hills with snow-pack and there aren't any rocks or log hazards like you might find mountain biking. You should give it shot!
5 years ago
How long are the skis that you used? And what bike frame did you use?
How would you take this on a ski lift?
Seems like it would be a blast to ride.
5 years ago
Version 3.0 should offer brakes on the handlebar like a regular bike, not for stopping the bike, just slowing it down. But great job, had a lot of improvements from 1.0
6 years ago
Nice but I don't see the use for the pedals. Anyway got my vote hope you win!
Just wondering how much of a hassle ski areas give you to bring this on the slope. Around here I am guessing they wouldn't allow it.
I would strongly advise calling ahead and asking if the hill allows ski-bikes. I found a hill in my area that allows ski-bikes through theAmerican Ski-bike Association网站，并没有麻烦。即使是驾驶架运营商也认为滑雪自行车很酷！
5 years ago
Very nice design! To me however, it looks like a great way to break my neck.
Hmmmm I'm thinking for my skill level something along the lines of a 3 ski would work for me. Low to the ground like the old school big wheels. I think you did an excellent job!
5 years ago