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Discussion Starter · #1 ·
I started building a small snowmobile. The challenge was not to build anything from a Ski-Doo or parts of existing Ski-Doo. But building something completely new from raw materials and standard part that are affordable. The only essential piece that comes from a snowmobile the track, there are also skis (which I had already) but I could do without it. This enables reproducibility without depending on expensive used or new parts that may become unavailable.
I thought of several chassis configurations, I chose to build thin tubular steel, for low costs (of purchase and welding) and robustness. It takes aluminum 2.5 times thicker to have the same rigidity, it therefore not remains a large difference in weight with aluminum. I evaluated all calculated the weight of the materials and parts before starting to build. Each component is designed to make it strong enough depending on the intended use without unnecessary weight and without high costs.
I decided to go with a first draft with minimum mechanical. 208cc motor (35lbs for the engine in full), no transmission (reverse) A mechanical (engine, brake, CVT transmission, gear, brake) is secured on the frame with four bolts, and does not exceed the width of the tunnel. The feet can go on either side! No chain case, with the low power and speed, the chain does not need to be in an oil bath. The chain is inside the tunnel. There will be possibility of change of gear quickly depending on the use.
The rear suspension weighs less than half of an original suspension.
The track, suspension and sprockets can be dismantled more easily and quickly than any Ski-Doo. It will be the same for mechanics.
The front suspension is home made poles without dampers. I bought dampers from Yamaha Phazer 2, but they weigh more than my entire chassis! So I can not use.
The total length is the same as that of Elan, the track is a 120 '' x 15 '' with ribs of 1.25 ''.
The driving position very advanced, suspension, traction and driving is was much improve than that of a Elan, the weight will be much lower. I think a possible maximum speed of 50km / h.
This snowmobile is rather a Élan improved than a Tundra 300. Maybe my next building would be slightly larger, with a 420 engine that more close to a 300 Tundra.


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How is the motion on that rear suspension? Just looks very odd. The arm will push the rear of the track back, which will be extending the shock, right? No wait, it would compress it as the suspension squished, but it just looks like they are at the wrong angles.

I'm also concerned with the attack angle of the track. It will either trench a lot in deep snow or just submarine the nose.

Might want to consider putting anti-stab on the front of the rails. That is a lot of pressure on those tips.
 

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Discussion Starter · #6 ·
How is the motion on that rear suspension? Just looks very odd. The arm will push the rear of the track back, which will be extending the shock, right? No wait, it would compress it as the suspension squished, but it just looks like they are at the wrong angles.

I'm also concerned with the attack angle of the track. It will either trench a lot in deep snow or just submarine the nose.

Might want to consider putting anti-stab on the front of the rails. That is a lot of pressure on those tips.
The angle behind the picture with the raised rear may sound misleading but the attacle angle is only 25 degrees. this is down from the average of series snowmobile.
I do not think you well see the suspension movement! The angle of the arm is perfect to ensure the constancy of the track tension as a function of the crash. The angle of the damper is just right to ensure good strength and the right place.
 
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Discussion Starter · #7 ·
That is a very interesting design. Is the 208cc motor a 2-stroke or a 4-stroke? Keep us posted.

Dan
Hi Dan,

This is just a 4-stroke 7hp at 3600 rpm, which has a potential of + 12hp.
The small 2-stroke engine are not available, unless you buy an old Tundra 300 has strong fair price for the engine. (Or a chain saw, but they are small and noisy)
This complete engine (Honda clone) costs about the price of a Tundra 300 carburetor boots !

the idea was rather made something reproducible.
There will be no speed, but as always it will be strong enough if the gear ration is corect.
 
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The first Doo's came with a 7 HP Kohler and they would carry two grown men and tow a sled full of supplies. I'm sure yours will doo just fine. You probably won't set any land speed record though! :laugh_old:
 

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I like your project. My brother always wanted to build a tubular steel framed snowmobile. The 4-stroke Honda motor will be interesting. If beefed up to 12HP it will equal the non-high-altitude Elan but have 4-stroke torque less affected by altitude and it sounds like your weight will be in the ball park. Elans ranged in dry weight from 248 lbs to 280 lbs depending on the year. An Elan's track was 114x15 so yours will be longer but some of yours is lost in the suspension travel. It looks like there will not be much to hang up on when the track sinks. You say that the weight will be lower than an Elan. That will be great if you can accomplish that. An Elan ski stance ranged from 23" TO 25". It looks like your CG will be a little higher so I'm wondering what your ski stance is? Your chain setup will be more like a motorcycle so there will be some stretch with time and it will get stressed more with the track than with a tire so I hope that works out. It is great that you are keeping it simple and inexpensive. I'll bet that it will be lots of fun to explore on and should be great on side-hills.

In some ways I picture it as between a snow bike and snowmobile. A single ski in the front and it would have been a snow bike but with a lot more flotation.

Dan
 

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The first Doo's came with a 7 HP Kohler and they would carry two grown men and tow a sled full of supplies. I'm sure yours will doo just fine. You probably won't set any land speed record though! :laugh_old:
My father had one of those,a '63 I think.Would do 18 to 20 MPH.Light as a feather,easy to get unstuck.Somebody really liked it,enough to steel it.I still have the owners manual and tool kit.
 

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We had a pair. One was a 63 the other was a 64. 63 had a 7 HP, 64 had a 8 HP. In real cold weather we would drain the oil at night bring it in the house to keep it warm. Then pour it back in, in the morning. Otherwise it started very hard, if at all. That may be a trick B550 has to use with his! I'm very anxious to see his video of the first trip out. Hopefully he has some deep snow to give it the real test!
 

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b550, I have followed along with some of your other projects; your engineering and fabrication skills are amazing. I suspect you have been planning and mentally building this sled for some time. This sled looks to be what the original snowmobiles were designed for: a vehicle designed to carry the rider over virgin snow.

As usual, I'll be following along and looking forward to seeing the Small-Doo on the snow.
 

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We had a pair. One was a 63 the other was a 64. 63 had a 7 HP, 64 had a 8 HP. In real cold weather we would drain the oil at night bring it in the house to keep it warm. Then pour it back in, in the morning. Otherwise it started very hard, if at all. That may be a trick B550 has to use with his! I'm very anxious to see his video of the first trip out. Hopefully he has some deep snow to give it the real test!
Some of these new 4-strokes designed for work seem to start much better than expected when it is cold. The Honda motor on my power washer fired up every time I have needed it to thaw out a pipe. I put a new Briggs and Stratton motor on my wood splitter that also seems to start well. It has been running about 10 degrees F in the morning (not cold by some standards) but I'll have to give the 6HP B&S single a try in the morning. And, the new synthetic 0-40 weight oils should help as Juspi mentioned. It will be very interesting to see how well it starts for B550. The fact that it is a single should help.

Dan
 

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Still many details to be manufactured, only for the direction there are more than 50 small pieces to be cut, weld, assemble.

I stayed within my calculations to estimate the weight, even a little better.
around the weight of a driver. Hope remained at 200lbs with the thin dressing and small components missing.

It's a bit of a mixture of past and modern.
Past: small mechanical simplicity easy to repair.
Modern: Driving position advanced, good behavior, comfort, lighter structural construction and stronger than a bent sheet metal tunnel.

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Discussion Starter · #17 ·
I like your project. My brother always wanted to build a tubular steel framed snowmobile. The 4-stroke Honda motor will be interesting. If beefed up to 12HP it will equal the non-high-altitude Elan but have 4-stroke torque less affected by altitude and it sounds like your weight will be in the ball park. Elans ranged in dry weight from 248 lbs to 280 lbs depending on the year. An Elan's track was 114x15 so yours will be longer but some of yours is lost in the suspension travel. It looks like there will not be much to hang up on when the track sinks. You say that the weight will be lower than an Elan. That will be great if you can accomplish that. An Elan ski stance ranged from 23" TO 25". It looks like your CG will be a little higher so I'm wondering what your ski stance is? Your chain setup will be more like a motorcycle so there will be some stretch with time and it will get stressed more with the track than with a tire so I hope that works out. It is great that you are keeping it simple and inexpensive. I'll bet that it will be lots of fun to explore on and should be great on side-hills.

In some ways I picture it as between a snow bike and snowmobile. A single ski in the front and it would have been a snow bike but with a lot more flotation.

Dan
The skis stance was 28''

The engine is it lower than an Elan, but the seat is upper, just a bit lower than a Tundra 300rf.

Thanks!
 

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Some of these new 4-strokes designed for work seem to start much better than expected when it is cold. The Honda motor on my power washer fired up every time I have needed it to thaw out a pipe. I put a new Briggs and Stratton motor on my wood splitter that also seems to start well. It has been running about 10 degrees F in the morning (not cold by some standards) but I'll have to give the 6HP B&S single a try in the morning. And, the new synthetic 0-40 weight oils should help as Juspi mentioned. It will be very interesting to see how well it starts for B550. The fact that it is a single should help.

Dan
I have 5 of the newer B&S,CARB compliant 1 lunges.They'er all easy starters but they all want LOTS of choke and throttle to start.Even on a restart after warm up they'll be happy with some choke to start.
 

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Many many small parts to be manufactured.

I did a control plate of trottle that does not pass by the governor. I motifier the clutch for a 4000RPM shifting rather than 3500 RPM

I glued the vinyl 2 times on the boards, I did not like the carbon fiber vinyl imitation once installed. I changed to orange and chrome. I would save 2.5 lbs with carbon fiber instead of aluminum, but it would have cost me $ 600 instead of $ 60 for aluminum.

The engine and transmission easily exit through the front panel.

The frame seems very rigid.


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Looking good - very functional. It looks like you are not that far away from your first ride on it. I'll be very interested to hear your first ride impressions. I like the front-end covering. You have taken on a very big project.

Dan
 
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