The process of putting skis on the Stampede has been a something I have been trying to figure our for a while. My big design point was it had to be simple bolt on mounting, anyone can build a new from end and I have always subscribed to the KISS principle (Keep It Simple Stupid). Design criteria were; the need for flex (don't want to tear up the servo), the ability to collapse during hard impact (don't want/like broken pieces and packed snow is hard). What I came up with was to simply pass a properly sized bolt through the stock front bearing carriers and lock it down by using a nut, then lock down the plastic ski support with another nut. I used my old stock bearing carriers instead of risking damage to my new RPM bearing carriers and bearings - your did keep the stock bearing carriers didn't you? This setup will in theory stay put unless you hit something hard.
Going back to my ABS plastic stash, I formed a couple of 7" Dubro style skis with side ribs and pop riveted on some homemade pivots. I used a couple of stainless-steel bolts and nuts to secure the mount to the pivots and used two safety-pins to provide the spring to keep the tips pointed up and avoid the skis digging in.
Snow-Pede - Pro Version (Part 2)
After a lot of testing, I came to the conclusion that my initial design had some short comings. The collapsing design did exactly what is was supposed to do, however it also seemed to collapse when it shouldn't have. The front stance needed to be a little wider on the skis so that the turning radius could be tightened down to something drivable.
Part I - Max Ski throw - about 20 degrees | Part II - Max Ski throw - about 45 degrees + about 15 degrees of chamber when turned. |
Although my ABS skis worked great, ABS plastic is not the best choice for points of stress or load bearing situations, and my bolt on mounts broke because of this. So we were back to re-engineering the front end for a durable solution. Another problem was flotation and propulsion. The front stock tires mounted on the rear with zip tires worked pretty well and was super cheap, but there is a reason why someone designed sand/snow paws, so I picked up a set of Proline SandPaws.
Snow Terrain Reality - Due to the reality of the size of most drifts and my dog's mission to create as may (what I have termed) "Sink holes of death" in any clear patch of snow, my dreams of high speed drift jumps and snow speed racing on an un-tainted snow covered golf course, just were not going to happen. As a result, expect that you are going to use your skis in 1"-2" of snow mainly in a road, frozen lake, or golf course, forget about the deep snow unless it has a really really hard crust on it. Also expect that you will only be able to traverse objects up to that same 2-3" range. I might as well have shot the Stampede into the ground when encountering deep "Sink hole of Death" created by my nutty dog out-running the Snow-Pede. He also thinks its his buddy that he should tackle...yeah, lots of fun for him. Bottom line - just as most RC snowmobiles, the perfect Snow-Pede conditions are 1/2"-2" of wetter snow or very hard flat crusty snow.
Ski Mounting – What seems to be almost bulletproof are some custom Polyethylene “Y” wishbones - Ski-Carriers that replace the bearing carriers and attach to the skis via Polyethylene half circles. By the way Polyethylene or HDPE (high density Polyethylene) is the same stuff as a white NSF plastic cutting board. I used an $8 3M .5x18x20 cutting board. Polyethylene is very strong stuff that can be cut and drilled just like wood. Polyethylene is also once of the toughest commercially available plastic products for load bearing situation, aside from Acetyl/Acetyl and some custom blended nylons. I basically duplicated the bearing carrier height, and attachment, the set-up allows you to just e-clip them in place of the stock bearing-carriers and all the stock camber links attach as usual. To make the connection to the servo, I used some steel 106mm or 116mm Maxx turnbuckles, a worm gear screwed into the ski-carrier topped off with a rod end. I used something different in the pictures, but I ended up using some Traxxas shouldered screws passing up into the ski-carrier steering rod end in the Maxx turnbuckle ball. If anyone is interested, I made about 10 extra the ski-carriers and half moon ski mounts, some fit better than others and need finishing/trimming and don't include any of the turnbuckles, screws, or other hardware. Although the spares are not plug and play ready, I'll be happy to send them out FedEx ground for $10.00. You will have to do some trimming and spend about $20 on the stock hardware and Dubro skis, but you should be able to screw Dubro Skis directly to the half moon ski mounts.
The Skis – The Dubro Snowbird Skis work great and are an easy solution. The 9inchers are probably the best choice (measure first), however the 8” ABS skis I made work great but are a little wider than the Dubro models. Now that I corrected the mounting, I can turn a very tight 1-1.5 ft circle. The skis do a great job of steering the vehicle (with the new mounts) and keeping on top of the snow, even the really light stuff. If the propulsion and floatation part was worked out these would be great.
The Tires - The Proline SandPaws are outstanding quality. The fit and finish of the tires was first rate. I was a little disappointed that the tires had a smaller diameter and were quite a bit narrower than the stock tires. In trying to achieve more flotation, these tires were a little counter productive, but it did provide the traction for forward motion in up to 2" or so of snow. I would recommend using front rims on the rear. This will give you a little wider more stable stance. I also moved the shock mount up two holes on each arm to add a little more clearance.
The Look - I was more anxious to get out an test the set-up so I haven't completed the finish work and dying of the ski-carriers. Once dyed in black, I think the Ski-carriers will look very cool and will last a very long time.
Supplemental Floatation - After some testing in 4" snow, I devised a contoured 8"x8" ski that bolted to the under rear side of the transmission support. Yeah, it was a good idea that kind of worked, but the tires really had a hard time moving the vehicle forward in that depth of snow. The set-up did easily float the entire truck in 12" of fresh snow powder, but wouldn't move. Don't bother on this idea. The only thing that will work in deeper snow is a track system with huge paddles. I
OK, the Skis look Trick, but so they work?
Omaha was blanketed with over 30 inches of snow in Feb 2004 when I developed and tested this project. The snow has been deep and ranged from light and fluffy to wet to frozen to crusty. So say the least I did a lot of testing.
The new "Pro version" ski's I engineered with a wider stance do work much better turn the truck great. The whole set-up also looks really cool zipping around in the snow. Bottom line is that although this is a really fun project, the Stampede is far to heavy to "float" on top of soft fluffy snow even with dual tires at the rear. When this happens, you will become very frustrated very quickly. Even sand/snow paw tires will drill straight down on the soft stuff. That relegates you to only running on harder packed or crusty surfaces or in snow less than 2"-3" deep and at this point skis have a very narrowly focused terrain use and is also tough or impossible to back up. The in-efficiency of basically running the motor wide open to keep the truck moving in even 1"-2" snow will make shorter 10 minute or less runs common, even with good quality 3000mh batteries. On harder snow surfaces, studded, zip-tied (which work the best that I've found), or chained tires provide the grip the front wheels need to turn the truck. Yes, the skis work and do a great job with keeping the front end up, and tracking in the right direction, but again this is a moot point until a track system can be engineered to support the weight of the truck.
From my experience, I'm glad I did this project. I now have skis if I need them and a solution to a narrowly focused terrain problem. I think I have perfected the snow Ski part of the equation but the bottom line is you will become frustrated at attempting to use a ski based machine in conditions other than 1/2"-2" of wetter snow or very hard flat crusty snow.
My recommendation is you will have probably have a lot more fun running in the street with front tires and rear sand paws jumping all the snow drifts and snow banks...and being able to back up.
Tires are fine up to about 2-3” of hard crusty, wet or powdered snow. I have found that snow/sand paddles work best, even on the packed snow. The contact area of even dual tires or Maxx tires on the back just did not provide the floatation and forward motion that is required to keep the tires from just sinking in during acceleration on deeper or powdery snow. Soft powdery show has a surface tension of about 1oz./square inch. There is a reason they have specialize vehicles call snowmobiles that will outperform any other vehicle on snow. As a result a track system is required for snow deeper than 2-3 inches. The good news is that it can be done, and a couple of people already have, however you can expect to spend between $200-$400 for all the parts to make it work right at full speed. Although I have found all the appropriate materials, and have developed a solution in my CAD program with all commercially available materials, which will simply bolt on to the Stampede and E-Maxx, I think I would rather spend the money on something else. After all we only have decent snow about a month out of every year.
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