Snowmobile conversion

[west0618]

Snowmobile Conversion Spring 2016

Parts used not counting the snowmobile itself and my transmitter...

Four 2.5mm x 6mm bolts (two to hold drive motor) $1.60
30 amp ESC
HK-30A brushless Car ESC w/reverse $15.75
18T brushless motor-HobbyWing EZRUN
07E-HobbyWing-18-T-2030-Motor $18.99
Receiver
Fly Sky FS-GR-3F $7.90

Servo Corona 939MG $5.97

Battery 800mAh 2cell Lipo 7.59

E-Z Connectors .99
2mm Swivel Ball Link 1.99
Push Rod 1.10
TOTAL $61.88

Started this the first of March

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As is, this is a nice unit…if you want only to run about on smooth carpet or thickly frozen over snow...and not too fast. But it is SO bad anywhere else that I finally gave up and started taking it apart to see if it would accept an upgrade to a brushless motor and decent metal gear servo for steering as my two 1/6th scale quad ATVs and my 1/6th scale Mini Cooper did. So far, when I open these “toys” up I find it is as if they were designed for just such an upgrade.
I first wanted to see if the drive system could be converted as I figured the steering should be the easy part.

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Lots of room under here…

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STOCK GEARBOX AND MOTOR --- WAY OVER COMPLICATED CRAP STEERING
With the gearbox pulled from the unit I found that the same motors that went into the ATVs should work well here. And amazingly enough I found that the motor shaft was perfect to accept the press fit pinion gear. I had to elongate the motor mounting holes about .020” on the inner side of each hole then it fit like a charm.

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Crap Brushed Motor compared to NEW MOTOR
I’m still learning from Derek the fine art of calibrating ESCs and, with his help, we got the electronics shown in the picture to all work as it should.

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Next I returned the gearbox with the new motor into its cavity and reconnected the rear drive belt assembly and secured all the screws for the rear suspension.
I then pulled out the so called steering mechanism and gutted it of all the internal gears except for the main one which I hope to attach the servo to through a ball joint.

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STOCK STEERING MINUS THE MOTOR --- GUTTED STEERING ASSEMBLY

As the plastic they used for this assembly is very hard…and brittle, I used extra care to mill out where the original crap brushed motor was and enlarged the hole for the old motor shaft so the it would JUST accept the Corona DS-939MG servo. I was even able to use the original plastic rear motor cap to secure the servo properly in place.

Hopefully you can see well enough that I used an E-Z Connector on the servo control arm and a 2mm Swivel Ball Link to attach to the only original gear in the gearbox. Simple…effective…and accurate.

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I struggled for a moment on this next part. Over-thinking it, I expect. The linkage that connects to each ski slips over the white Nylon boss on the front of this assembly and floats on it to a degree so it would self-center with another assembly I have long since removed.

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Then it hit me. This piece is beefy enough that I can drill and tap two 6/32 holes on opposite sides and put set screws in them giving the control arm another adjustment point.

With the control arm drilled, tapped and installed, it was simple enough to get this assembly remounted and the front linkage reconnected.
Hardly competition grade steering linkage but that is not the intent. Just some 1/6th scale fun. I do wish it had adjustment on each side for alignment but until I see it run in snow…that can wait. After all…this is still a “toy” for the most part except that it can now go through anything.

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Now to set the Dual Rates on the travel right and left so it does not bind at either extreme then to try it out. A little masking tape to hold the electronics in place and out of harm’s way…and we are off.
The trial runs down the carpeted hallway were great. Now to mount the electronics to a final location and trim/tie back any excess wiring.
Fabrication of a plate…anything…to hold the receiver and low-voltage alarm (I do like these alarms) is simple enough and there is PLENTY of room under this body. I just cut a piece of some material Derek gave me, drilled to holes in it to fasten to existing mounts and secured the receiver to the top with Velcro and the lox-voltage alarm to the bottom with a two sided tape. I did end up turning this plate over so the receiver was on the bottom and the LV Alarm was on top thinking the servo wires may set too high. The ESC is the perfect size to fit into the front of the old battery compartment with a piece of Velcro on the bottom. I was able to use the original ON/OFF switch and wire it into the ESC. As I do not plan to get any great distance when running, for now, the antenna will simple lay in the front under the cowling.

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This thing originally ran (poorly) on 8 AA batteries measuring 1 ¼” square by 4 7/8” long. Even with the ESC in the old battery tray, there is ample room for an 800mAh lipo. I could easily put two of these in there if I wanted to.

As my converted 1/6th scale quad ATVs run 20-30 minutes hard on a 350mAh 2cell battery so I figure I should not need much more than that for a decent run…especially in the middle of winter. So 800mAh seems a good starting place. And there is room for two of these if I wish as I do have two.
The ESC I chose does not have a connection for the head and tail lights so I intend to use the spare connection for a fan to power them so they will be ON when the snowmobile is on.

[DOG]

That's a neat looking snowmobile. Need to make a video when you can.

[Stambo]

Looks like fun, looking forward to the video.

[Graham Lawrie]

Excellent thread and build yet again:)

[cml001]

Hell yeah!

[Derek]

Nice one, Dad!

Its pretty clear that Dad is much better at documenting his builds\conversions better than I am lol

[cml001]

Lol

[west0618]

Thanks for the kind words as I feel most of you are fliers and here I am again on the ground. I have to be careful with this thing now indoors so I do not melt the carpet. Details and documentation come easy for me as my world, before retirement, was measured in millionths of an inch and I had to teach those around me as well. It drives Derek nuts when I make something for him and he expects me to measure with a ruler and I get out my micrometers. Close is rarely good enough. Then he gives me grief when I miss it by half a thousandths. LOL This conversion was WAY overdue and with the lack of snow this season it seemed like a good time to attempt it. That being said, we will all have a fair wait for the first good outside run…in any snow. Thanks for reading.

[DOG]

It doesn't matter if it's in the Air, water or ground, as long as you are having fun in the RC World, that's what counts. My self I like the thread, build and videos. I always learn something new from this site. Thanks!

[Derek]

Although we probably won't be getting much snow in the near future (not complaining, lol), Dad may be able to take the new snowmobile to our club flying field. The short grass runway is very short and I imagine the snowmobile would do quite well. We'll see about getting to the flying field soon and we'll give it a go.

[Marius]

Nice build, Derek's Dad! I have that exact same chassis, although my model is a tad larger

[Lee]

Great job man!
Could you not have scrapped the steering gearbox completely, and just had a servo as a direct drive, in the centre?

[Derek]

Great job man!
Could you not have scrapped the steering gearbox completely, and just had a servo as a direct drive, in the centre?

Actually, he did scrap the gear box and he's using a Corona 939 servo for the steering. A couple of the above pics show the servo in place.

[Lee]

Great job man!
Could you not have scrapped the steering gearbox completely, and just had a servo as a direct drive, in the centre?

Actually, he did scrap the gear box and he's using a Corona 939 servo for the steering. A couple of the above pics show the servo in place.

I see the servo Derek, off to the side, linked to the big cog then to the steering arms.
What I mean is to remove the whole plastic casing, and only have the servo by its self in the middle, directly connected to the two arms.
Should free up space for other goodies

[Derek]

Great job man!
Could you not have scrapped the steering gearbox completely, and just had a servo as a direct drive, in the centre?

Actually, he did scrap the gear box and he's using a Corona 939 servo for the steering. A couple of the above pics show the servo in place.

I see the servo Derek, off to the side, linked to the big cog then to the steering arms.
What I mean is to remove the whole plastic casing, and only have the servo by its self in the middle, directly connected to the two arms.
Should free up space for other goodies

ohhhhh, my bad, Lee! I see what you are saying!