Jay-Em

ooohh..

That reminds me: Time to take the Kyosho WaveChopper out again. I fixed a real jet drive in it(Graupner mini-jet) Still trying to figure out the right motorwind. Currently it's a 17-double. Sortof works, runs a bit hot ,despite watercooling.

SkiDoo works admirably with the wheeled ski's and double touringcar dampers in the rear. Removed the torsion-bar from the front. It works great on tarmac, but gets rather unpredictable on rough ground.

Well ,lose some, gain some.

I really like the motorcycle. I've been looking at that Italian clone (AR5?? or something) but it's waay too expensive for me.

TechyJoe

Just adding some browser key tags so folks can locate this page better using Google etc.

rc snowmobile, rc skidoo, RC snowmobile, RC Skidoo, rc ski-doo, rc skidoo rev xp, radio control snowmobile, radio control skidoo, modified rc snowmobile, snowmobile hopup.

subcaptian

Hey guys, I'm starting a buildup of one of these XPs too. But for the motor I'm going with a castle creations sct system, which means I need a custom tranny. I already decided on a belt-style system, any suggestions on gears?
Thanks,
Subcaptian

TechyJoe

SubCaptian

I've been kicking the idea of building another Rev XP using a 540 brushless motor as well and using a belt drive. I actually have purchased some gears and belts to try it out but I haven't gotten to building yet. I'll shoot some pictures of my idea for this and post them. This may help inspire you with some of your own ideas.

subcaptian

Thanks for the support man, maybe we can collaborate on this effort. So far, I've been working on a suspension setup modeled on the FAST M-10 system, my only issue being dampeners. For the motor mount and suspension "slides" (Not really slides as the track rests on the wheels). I'll try and get pictures up of my blueprints and cardboard mock-ups. So far, everything looks good, I just need a belt system and short enough dampeners.

sokey70

I ended up drawing some skids or side plates but can't find anyone to cut them. If you can post your prints or plans I would like that. I also got a Polaris I'm trying to work on.

TechyJoe

Dura Trax has several smaller shocks. I used some of these to replace the stock friction shocks and they seem pretty durable. Team Associated has many different springs and shock parts as well.

I used the longer ones to replace the front shocks and I used the original stock springs.

Tower Hobbies.
http://www3.towerhobbies.com/cgi-bin...?&I=LXRAG4&P=7

http://www3.towerhobbies.com/cgi-bin...?&I=LXLLX1&P=7

subcaptian

Nope, those won't work. I took the front shocks off my RC18 to try on the rear suspension, and they're too long. It needs to be a touring car damper, or maybe one from those Losi 1/24th scale vehicles.

subcaptian

Oh, and sokey, I'll try and scan the blueprints soon. For cutting the metal, I just found out that my highschool's sister school completed its 2 axis CNC plasma cutter, and it makes a really fine line, perfect for screw holes and seamless cuts. Best of all, I may not even have to buy the aluminum, since their shop class has small aluminum scrap. We'll see how this turns out...

TechyJoe

Here are my napkin doodle designs or napkin prints.

The first picture depicts the motor, gears and pulley setup. The second picture depicts a side view of all the stuff on a motor mount. Best I can do for low tech.

TechyJoe

Ok, here is me and my big fingers holding the parts I purchased together on the chasis without a custom motor mount to hold it all in place.

Note:
I didn't have a brushless 540 motor available for demo so I used a 540 brushed motor from a Traxxas Slash (this demostrates the idea).

The parts fit "almost" perfectly but I think I'll still need to cut away some plastic to fit them correctly and add a pulley tensioner to tighten the belt.

I'm a little worried that the spur gear I selected won't hold up to the 540 but it does fit in the small space.

subcaptian

Well, these are my designs. The motor mount is actually on a cardboard sheet for fitment, but the suspension is still on paper. There are mock ups of it though if you want pictures.

subcaptian

By the way, Techy, looking at your motor you may want to move it farther forward. I hear these sleds get really light on the skis when accelerating, and a 540 has room to fit further up. Just making an observation.

TechyJoe

Subcaptain

Yes, agreed, that thought came to me as well after looking at your offset design - thanks.

Also note: Since the motor is totally enclosed in the hood shroud, things get really hot inside so cooling considerations are important. I added one of those clip-on motor fans to my 480 motor to try and keep things cooler as well as adding some venting. Pretty sure the 540 motor will really heat things up.

This brings up the topic of weight, we don't want the sled to be too heavy or it will just sink and the power of the 540 will just help to dig holes in the snow.

I've also been considering cutting off ever-other track tread lug to help keep the sled ontop of the snow.

subcaptian

Why would cutting off tread lugs help? And, about cooling, I took out part of the front black piece, right where the normal cooling vent is. I also put 6 holes on each side in the cowling in front of the rider. (Mine doesn't have one, though... ) And, to top it off, the SCT system comes with a great motor fan.

TechyJoe

Well to answer your question, I don't have a real snowmobile but from reading some things, my understanding is that when real sleds are in deep snow, you typically want a longer track and one with less lugs because it "digs" less, which makes sense to help keep the sled ontop of the snow better.

The track on this model is very narrow which is bad - you want a wider track to disperse more weight to stay on top of the snow but since widening the track is not an option, less lugs may be the next best thing. The New Bright Ski-Do is much better suited for this since it has a much wider track.

I have a spare track so I'm going to experiment with this as soon as we get some darn snow.

TechyJoe

Subcaptain

have you seen Jazzka's suspension design? I started a wood/cardboard model of a suspension about a month ago which is a highbred between his and your design - but never completed it. Jazzka's suspension seems to work well. So, I have taken a snapshot of it and added my placement of the oil filled shock.

Here is a link to his youtube video. You should check it out.
http://www.youtube.com/watch?v=O2b_a...eature=related

subcaptian

Well, on that note, do you think it would be better to try and emulate his or continue with the m10 style setup?

sokey70

Thanks for the pics, any chance you have them drawn in CAD?

Techyjoe - I am thinking the same style of setup with the shockplacement. What are you thinking of using for swingarms between the skids?

What are your thoughts on a track/skid system like this one?
http://www.rcuniverse.com/forum/m_8206222/tm.htm

Seems pretty basic yet functional.

TechyJoe

Subcaptain
From my experiments and because of the small size of the suspension, I think your going to want to add the pivot bars I circled in yellow regardless of how you mount the shocks. This is because the pivot will give you more up and down travel of the suspension.

Sokey70
Good suspension mods. Just keep in mind like a stated above, our model is 1/8 scale - very small. I think that model may be larger, more like the 1/5 scale New Bright Skidoo.

Oh, and for swing arms, I was planning on using some thin aluminum bar stock purchased from Home Depot and then cut it to size/shape using a Dremel.

subcaptian

Hey, Sokey has a point. That Polaris is in the same scale and manufacturing type as the Ski-Doo XP. Which means, the suspension is already mapped out, we just have to build it. Plus, it looks pretty realistic. Good find man. Now, I just need to get a Traxxas Stampede aluminum arm and an RS4 arm. Simple!

TechyJoe

I looked up the Polaris fusion 900 on the web. It's a 1/6th scale - 24" inch sled. I have the Skidoo MXZ version of this. It's much larger. There is also a picture of one of these Polaris's on the site the Sokey70 provided next to a tape measure if you go to page 2 and scroll down a bit.

subcaptian

Well, if we know it's in 1:6th scale, couldn't I just size down the Stampede and RS4 arms? Oh boy, more CNC plasma cutting.

sokey70

If we look at this picture I think we can make the same basic skid layout and mono shock design without getting overcomplicated. I was fortunate to score a Rev XP as well as the larger Polaris. I ended up purchasing the bulkhead and swing arms that are mentioned in that thread for the from suspension. As for the rear, I couldn't find the RS4 arms but I have access to 1/4" thick lexan and was thinking I would just measure out what I need, cut it, and drill a hole for the arms to pivot on. Let me know what you guys think. The only think really holding me back now is getting the CAD and aluminum skids cut by someone.

I've even thought about a dual shock design like so and making the swing arms out of small metal rod. I haven't fabbed much so this is all just flowing from my head, not sure if it's good. Thoughts? Now that I'm thinking about it a dual shock may be just too much for the smaller sled, especially getting front shock that short with good functionality. Here I am rambling. Post your thoughts.

subcaptian

I'm getting the aluminum skids and motor mount cut today. Sokey, the suspension you posted is the M10 model, the one mine is a copy of.