How to Create a Downhill Ski-Bike 2.0

滑雪自行车是一个宏伟的对手，使用自行车固定在下坡滑雪板上的自行车的基本元素乘坐雪坡。

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.

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.

Ski-Bike 2.0的首要任务是设计和构建钢的安装支架，以实现最大的刚性和耐用性。

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:

1. 将角度熨斗和管钢切割成我的设计预定的长度。

2. Weld the pieces together.

3. 构建轮毂和轴组件。

4. Drill holes in the angle iron to line up with the ski binding screw holes.

5. 钻在支架前面的孔中的孔螺栓（稍后讨论）。

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.

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.

一个更好的选择是使用一套双胞胎尖端的滑雪刀片（又名滑雪板或雪滑板），允许向前滑动相同的控制。滑雪刀片类似于现代下坡滑雪板，但显着较短，往往超过90到100厘米。这个长度范围已成为滑雪自行车的非官方标准。对于滑雪自行车2.0，我获得了一组约94厘米的滑雪刀片。

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.

以下是两个技术自行车术语，有助于澄清以下部分。

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).

在其作为普通山地自行车的日子里，Ski-Bike 2.0框架有一个带有100毫米行程的叉子。将其转换为滑雪自行车2.0时，我将原始叉形取代为130毫米的旅行。130毫米叉的行进比100mm叉30毫米，因此更长。这种长度的增加升高了头管，减少了头管角，当指向下坡时，使给我更自信的转向和控制。

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.

对于滑雪自行车2.0，我想出了使用单轮脚踏车曲柄武器的想法。独轮车曲柄手臂工作得很好，因为它们仍然允许踏板改变位置，没有链环担心，并且有各种长度可用。我决定使用真正短的曲柄手臂来弥补具有零阻力的长曲柄臂的不安感。具有短曲柄臂导致踏板的旋转直径更小，最大限度地减少旋转曲柄的效果零电阻。较短的曲柄臂的另一个好处是相对于地面的间隙增加。

我选择使用山地骑自行车平台踏板用于滑雪自行车2.0，因为它们具有宽阔的脚踏板和大型铆钉，可以额外抓握。

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.

另一方面，滑雪自行车2.0旨在为任何东西做好准备。前雪橇由安装支架前部的蹦极保留系统控制。蹦极处于恒定的张力，同时滑雪在地上，总是试图向上拉滑雪的前端。蹦极穿过安装支架前部的孔眼螺栓，并使用坚固的不锈钢线撞入环路。蹦极的顶部撞入一个带有更多电线的环，环绕在“S”钩子上，然后将“S”钩子挂在自行车叉的桥梁上。我削减了蹦极的长度，以达到张力的正确平衡。一旦机载，太多的蹦极张力会迅速向车把上拉滑雪尖，张力太少可能让滑雪尖端潜入地面。

对于后肢滑雪，我要钻机类似于前滑雪的蹦极保留系统，但我遇到了一个扭转弹簧，似乎是正确的尺寸，具有足够的弹簧速率（即弹簧的强度）。弹簧的内径大于轴的锁紧螺母，使其在顶部滑动，并按压安装支架的下侧和自行车框架的辍学件的轴切口。

One key attribute of these two systems is that they both can easily be disengaged when needed, such as during transportation.

这一步骤完全是可选的，但非常有效地为项目提供专业和完整的外观。我有自行车框架和安装支架粉末涂层，涂层非常耐用，但需要零件在烤箱中烘烤以硬化涂料。由于滑雪板含有很多塑料，这可能在烘焙过程中可能融化，我无法粉末涂抹它们，所以我只是喷涂它们。

我为框架选择了一片黑暗的金属蓝色，以便在用白色的雪背景观看时突出它的形状。滑雪板和安装支架被涂成白色，融入白色的雪背景，造成骑自行车的幻觉只是漂浮在雪地上。

Ski-Bike 2.0的性能是滑雪自行车1.0领先的巨大步骤。我能够自信地滑雪，以合理的滑雪山快速作为典型的滑雪者或滑雪板。当我打开把手时，前面的滑雪挖了它的边缘进入雪中，让我雕刻扫一圈，每当我想要的时候停止。每次改进都很明显。

Here is a quick summary of each improvement made to build Ski-bike 2.0 and the resulting performance increase:

• 使用小型全悬架自行车架=较轻的重量，更易于处理
• Building mounting brackets out of steel = noticeable increase in rigidity and ability to fasten to ski via screw holes
• 通过安装支架尺寸降低轴高=较低的重心使转动和倾斜更容易，更自信
• 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!