TechyJoe

harryfish

Yes, lots of people ask how to get these stock pinions off. The quick answer is that it is almost impossible. I always just replace the motor. You can purchase a new pinion for the new motor just get a motor with a 3mm shaft (I think I listed the pinion number above in the thread).

To answer your second question: my ski-doo only has about 2 hours of run time on it. The transmission gear box itself held up but the second gear from the pinion (the one which converts pitch from 48 to 32) stripped fairly quickly. I replaced both the pinion and this second gear with two metal gears. Each gear is the same size and I believe they are 14tooth 32 pitch. I also had to replace the gear axle and change it to 3mm rod.

This reduces the gear ratio by about 1/2. That is, the gear reduction was reduced from about 8:1 to about 4.3:1. This increases the speed of the sled but reduces the power and also causes the motor to heat up more.

I also attached the stock cooling bracket to my new motor and cut out a small hole in the front of the sled (where the radiator would be on a real sled) to allow cool air in to help cooling.

My motor is 4000kv and it would probably run better and cooler if I reduced it to about 2000kc to 3000kv with the new gears. But, the way it is now, it is very fast.

I will try to attach some pictures and the part numbers for the new gears.

I've also done some others mods recently which have not been included here yet. This includes revamping the stock front shocks to get more travel. I'll post more on this later.

Lorduss

[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXYCE5&P=7]pinion gear puller[/link]

pinion gear puller, should work for those motors, there are other brands to.

harryfish

Thanks Joe for the reply, just did the track tension mod and noticed a bunch of hair line cracks in the track. Have you notice any cracks on yours? Hopefully i can just glue them before they get worse. I'm having a hard time with the gearbox trying to find a stronger trans that will fit,
maybe a crawler trans? I think the best set up would be two pulleys and a belt like something out of a touring car.

Harry[8D]

TechyJoe

harryfish

I don't have any hair line cracks in my track. My guess would be that somene drove the snowmobile through ice melt / salt and this dried out and cracked your track.

Note: I purchased a second one of these sleds for spare parts just for this purpose.

I also thought about building a custom belt drive train but there is not a lot of room to gear it down but I may try this with the spare parts sled. Let me know how you make out with yours.

I have also attached pictures of my gear train and the part number for the pinion I used.

TechyJoe

Here is a picture of the new gear drive with metal pinions and a new 3mm gear shaft (cut piece of 3mm drill bit)


Pinion part number (From Tower Hobbies): TRAC3944

TechyJoe

Here is a picture of my modified front shocks.

I chose to keep these instead of replacing them with oil filled because oil filled shocks that fit the space seem to be weak. The stock ones seem very strong and work pretty well (I want to eventually jump this sled).

I took these shocks apart and re-adjusted them then I added some white grease to make the action smoother.

I was able to add almost 1/4 inch of travel to the shocks.

TechyJoe

Here is a video of the my Rev-XP in snow.

This video was taken before the new gear train mods listed above:

[youtube]http://www.youtube.com/watch?v=Owo6LHFgXCE[/youtube]

TechyJoe

Snowmobile season is approaching once again.

I added some new suspension upgrades to try and help keep the track to the snow by replacing the cheap rear suspension shock (tension wire) with some oil filled shocks.

I'm presently experimenting with two versions of this.

The pictures show the cheap tension wire and the replacement system with a mono-shock and a duel shock setup. I tend to believe the mono shock is not stiff enough so I will probably go with the duel shock system.

TechyJoe

I also added a cooling input port to the front of the sled and exit ports on rear of the motor cowl to try and keep it cooler inside the motor area.

TechyJoe

Jumping my Skidoo

Next year, I'll try a bigger ramp.

[youtube]http://www.youtube.com/watch?v=8Z3LZVoKhxk[/youtube]

TechyJoe

I changed the pinion gears from above.

The motor pinion used is the same Traxxas 32P 14T pinion listed above (3944).

However, I changed the middle idler gear to a Robinson Racing 32P 14T pinion. Part number: MS# 0140, Tower Hobbies part number: LXEW99

The Robinson gear fits in the tranmision case better than using two Traxxas pinions.

TechyJoe

Some other final changes:

1) I changed the motor to a Himax 2300kv brushless from the previous 4000kv for the new 4.5:1 gearing (RCDude.com).
2) I re-enforced the gear housing with fiber glass and added washers around the idle gear's axle and fiber glassed them in place.
3) The idle gear axle is now 1/8 round stock and I drilled a hole in the gear case so that the axle extrudes to the outside of the gear casing (see the picture) and I capped it with a wheel collar to hold it in place.
4) Changed the batteries to 7.4v, 2200mah, 25C.
5) Removed the stock headlamps and replaced with 2 super bright xenon bulbs wired in series.

Jay-Em

Just want to say "Thank You" to the OP.

TechyJoe

Cool, glad it helped.

I'd love to see some pictures and or video of yours if you can.

I'll suggest you re-enforce the gearbox area where the motor bolts to the plastic housing (inside and out) with some fiber glass. This area is weak and the torque of the motor may rip through it and then your grears will strip.

Jay-Em

A video will be problematic ,as I do not own a vid-cam.Speed is currently about the same as a stock grasshopper. Say about 11mph, no more. It accellerates pretty good, and even better on wet grass. It tracks nice and straight with the damper hop-ups and the Hi-Tec high-torque mini servo (metal gears!, saves me the hassle from having to cobble-up a servo-saver).

TechyJoe

Looks great!

Two questions:

1) What front shocks are those? They seem to fit nicely and look sturdy.

2) Where did you get the motorcross helmut for your rider? - Very cool.

Jay-Em

Front shocks are ancient. They are from a Vintage "Marui Galaxy" , and fit like a glove. (google Marui-Galaxy RC buggy parts. Sometimes parts, like complete Marui Galaxy shock-sets, soft springs, hard springs and soft and hard pistons) come-up on e-bay pretty cheap, cause they are not as collectible as Tamiya vintage.) I had those for, like, 15 years, bought them for a monster-truck project that never materialized. I filled them with 300WT oil. Seem to be the best balance between tipping-over prevention and road holding. Current springs are the stock Ski Doo ones, but they are a bit too firm, though they look great!
-cylinder dia: 8mm.
-length eylet to eyelet: variable between 6 cm and 7 cm, depending on chosen piston.
-piston: standard 3mm - one-piece

I am still experimenting with several springs. Be forwarned though, They are a filling-nightmare, and the copper knurled cap will leave one's fingers raw.

To be honest, every oil-filled shock with a length of about 6 cm-eyelet-center to eyelet center- and a diameter of about 1 cm, or less and a piston of 3mm (for strength) will fit.

Moto-cross helmet is a repaint from a 1/6th scale Graupner RC toy moto-cross figure. With some searching in the 2-for one-bin at Your local Toy's are Us, it is often possible to score an action-man figure for little. They often have all sorts of cool helmets and gear. Figures are the right scale too.

Jay-Em

Update:


I tried the 3600kv speed 400 6v.

Not a good option, unless one would like to go to an 11-tooth pinion (an educated guess). With a 16-tooth, a speed400/6v has a good top-end, but accellerates sluggish and battery and motor run very hot.
With a 400/6v on 7,2v and an 11-tooth, You'll prolly' get some nice extra accelleration, but loose out on the top-end.

I machined-out the idler gear to fit tiny ball-bearings that I had lying around. No idea what size.
It fit the axle with the help of one of those copper eye-lets that come with servo's. It helped some in the noise -and wear -department.

I also ceramic-greased the axles of the bogey-wheels and idlers. That helped tremendously in the squeeck-department. The track runs pretty smooth, and doesn't "flap" around so much.

QUESTION:TechyJoe, how did You get the idler-wheels off to open-up the track "box" ? I tried brute force and some leverage, but it only succeeded to crack the track-"box" for a bit. Cyano-Acryilic to the rescue
I figured that, with some luck, there are flanged-bearings that will fit the bogey axles. I am somewhat sceptic about the wear-resistance of those holes in the plastic. Plus I want to install two oil dampers like You have. Under heavy load, the track hasn't got a whole lot of throw left, and slams in top of the tunnel when riding on really rough surfaces.

TechyJoe

Jay-Em

You are correct about the pinion gear reduction. If you use a 12t, 48p gear as your pinion, your motor should run cooler and you should get decent low and top end.
I purchased a set of axtra long 12t, 48p pinions for a heli (mini Titan E32 3D heli) from TowerHobbies (not used since I changed the pinion and idler to the 14t, 32p gears)

I changed my 4000kv brushless out to a 2300kv motor after I burnt the 4000kv one out from changing the pinion and idler gearing.

The 2300kv brushless gives pretty good low end power and top end speed (at least when in snow) with the new gearing.

As for removing the wheels in order to open the "track box", that was a little tricky. They are just pressed onto the axles but getting leverage on them is hard. I wedged a large flat head screw driver between the wheels and the track box and twisted the head to pry the wheel off. You need to be very careful when doing this and take your time because you can easily crack the plastic or crack the inner white spacer wheels.

It's getting late here so I will try and provide a picture of what I did tomorrow.

Also, I purchased a spare skidoo because I ripped my first gear box apart using the new motor and broke some other things along the way. This is a good thing to have because now I have "extra" parts.

I think I am going to add another axle/idler wheel set just above the final rear axle to try and tighten up some of the track slop. I have found that when cornering sharply, the track tends to slip off the rear axle wheels. I'll take a snapshot of what I am thinking here as well.

TechyJoe

1) Large flat head screw driver prying off the wheels
2) Prying off the wheels
3) Screw driver and wheel assembly
4) Picture of longer 12t, 48p gear for the stock gear system
5) Prototype of extra axle and wheels to adjust track slop and for holding the track in place. It would be neat to place this on a damper (shock/spring) which could adjust tension as the track moved up and down.

Jay-Em

Heh, funny You mention it. I am about to order a second ski-doo at Amazon.
Edit: I just did order a new one...Sadly the new ones do not come with a driver-figure like Yours. Where did You get Your Skidoo-with-driver?

Suddenly thought of something: wouldn't it be possible to slot-out the rear wheel axle-holes, like the slot that holds the suspension axle?. You could fix a spring-loaded tensioning slider -think model tanks- on the rearmost wheel, instead of just drilling a new hole 6mm back...
I think I am gonna try that.
For now I'll use a bit of bike inner-tube to glue around the idlers. It tensions the track for a bit untill it stretches again.... I am still pondering a true rear-track. I've seen some home-made alu beauties for the New Bright Arctic Cat

I put a 12-tooth on the 400 6 v. It is as balanced as it gets I guess. I got 15 minutes from a 1200mah, mainly on flat tarmac though, but with a LOT of accellerating and braking. Technically the 400 is at it's best efficiency when using 4 Ah. (= 18 minutes theoretically) It has a nice top-end now. Still nowhere near to brushless. It does 11.8 mph (GPS!) with the 6v+12tooth pinion, and 9,8 mph on the 7,2v with the 16 tooth pinion(buuut..it runs for more than 20 minutes..choices, choices). I'll have to fix me some 9,6v packs to get 15mph out of those little 400's

Track slippage is becoming a bit of a problem, so I think I'll implement Your "paddle" solution for the drive-wheel.

Sadly I rolled it a bit too much due to too stiff spring-tension, and my handle-bars are starting to rip. I'll have to make some from aluminium stock, or brass.
I lessened the tension of the front springs, though fearing it would sink too much, it actually worked very well. Soft front-springs fix the roll-over problem. It does look a bit squirrily on the rough, but the dampers seem to do their job. I have far less rollovers.

TechyJoe

I purchased my Skidoo with rider from Ebay. It cost me a little more than the one without the driver but it looks better. I haven't seen one with the dude on it in quite some time.

As for the track tension system with the paddle solution, be careful. The paddles work great for eliminating all slippage but tensioning the track from the back axle causes the track to bind around the top of the drive paddle wheel.

I moved my rear axle back to the stock position to remove the binding but this put slop back into the track causing it to slip off some in turns at speed.

I little trial and error has shown me that tensioning the track where a placed the extra axle works the best.

Also note that your skidoo rolling may be caused by you letting off of the throttle to hard causing the skidoo to naturally break. I was doing the same thing. Try reducing your speed more slowly and not allowing so much breaking action. I'm using a brushless and have programmed my ESC for lighter breaking and I also let off of the throttle very slowly now. I also added "tip" over bar to the rear to catch it before it rolls.

Note: You can fix the handlebars with a small piece of wire. The rubber is soft so the wire can be pushed in to both ends of the ripped area and then glued in place.

Jay-Em

Nah... It only rolls because I tested on tarmac, and the front wheels have pretty good grip. It only rolls if I steer too quickly when accellerating. When there is snow next winter, and the Ski-Doo still is among the living , I think the sliding ski's will be good enough to prevent rollovers.

I fixed the handlebars like You said, with a piece of 3mm threaded rod<meta charset="utf-8">. Works like a charm. The rubbery stuff the bars are made off, react great to cyano-acrylic glue. It's sturdier than it ever was.

I also succeeded in fitting two 1:10 touring-car shocks with 2-hole pistons, 450WT oil, and medium springs in the track-box. They are connected to the spring actuating-bar and a couple of long screws on the lower part of the box, all of it without prying the wheels off. They were a bit fiddly to get in, but it works. I can now easily adjust spring hardness with those standard horse-shoe shaped spacers Tamiya touring cars use. It jumps nicely without bouncing after landing. I jumped off ever higher curbs to test it.

After some reading on snowmobile sites, I decided I will fit anti-roll bars to keep the sled planted in flat corners. It seems a standard problem of snowmobiles to wanting to roll while cornering...bit like my ATV (I got an Access/Apache) and without a driver capable of counter-hanging it just rolls into the outer-ski and falls over. Anti-roll bars should fix that at the cost of some rough track handling.

By the by, funny how our little "toy' ski-doos have the same handling problems as their big brothers ,and, basically the same solutions apply...

I'll post some pics when the anti-roll bar is in.

Thnx again for the tips and tricks.
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Jay-Em

Well. Anti sway-bar works!. It is ,sadly, only push, and not pull due to space restrictions. I'm still thinking about a way to get a "pull" sway bar, because that's a bit more effective. The current swaybar center, however, doesn't fit around the cowl. Maybe cut it in half and make it wider in the middle.... *pondering* I could go the whole way and copy the tube-mounted sway from a real Ski-Doo.......Hmm....

This is how I did it with the help of a TA-05 swaybar set for Tamiya touringcars. They come in 3 hardnesses. Yellow is soft. I think I'll use blue (hard) on the street, and yellow in the rough and on snow. It seems a good balance between anti-sway, and suppleness to absorb bumpy ground.. It is still a ptototype test. I had to cut off 1cm from the ends, to prevent it from interfering with my suspension arms, though.

I also added some pics of the frp motor "heat shield" and the ball-bearing equipped idler-gear.


Hmmm...pics are a bit of a problem it seems..network's slow...

TechyJoe

Neat idea.

I don't know much about sway bars. Keep me posted if you implement any new features such as the track tension system.

No snow left and it has been gone since February so I've put my sled away until next year. It's time to break out my other summer time toys.

[youtube]http://www.youtube.com/watch?v=YrFUPtW0ClU[/youtube]

[youtube]http://www.youtube.com/watch?v=g13NLBdlYOM[/youtube]

[youtube]http://www.youtube.com/watch?v=qtTYKMt1SWM[/youtube]

[youtube]http://www.youtube.com/watch?v=vTeCra1PeWQ[/youtube]