*Open source purpose built snowmachine design thread*

[NEWDUCK]

485# - 10 gallons of fuel @ 6.2 lbs/gal.= 423# dry
Is this without bodywork?

With just a belly pan and no hood. I dont run the plastic that goes around the tank. I lost quite a bit of weight ditching the stock seat and getting rid of that heavy skid.

The tube frame is steve samps first one they made. They were going to throw it in the garbage so I snagged it for some mock up work.

 

[roo]

With just a belly pan and no hood. I dont run the plastic that goes around the tank. I lost quite a bit of weight ditching the stock seat and getting rid of that heavy skid.

The tube frame is steve samps first one they made. They were going to throw it in the garbage so I snagged it for some mock up work.

In the snowhawk world thats pretty slim numbers. I need to get a bigger scale to hang mine from. Scared to see real weight!

I really want to see low numbers in my future build. I will use carbon fiber where i can. I think the 375# range is pretty realistic, and still have it be fling into the trees tough like it is now.
Nice work!

 

[Sheetmetalfab]

In the snowhawk world thats pretty slim numbers. I need to get a bigger scale to hang mine from. Scared to see real weight!

I really want to see low numbers in my future build. I will use carbon fiber where i can. I think the 375# range is pretty realistic, and still have it be fling into the trees tough like it is now.
Nice work!

Mine is tree fling ready.

https://www.snowest.com/forum/showthread.php?t=376728&page=2

 

[roo]

Originally posted by KAARLONEN

Like this? Simple A-arm front suspension with hollow carbon sliders.
Also my motor of choice. Centered mass and enough power

Wouldn't this front suspension design require linkage in the A arm?
Without linkage I dont see how you could match the straight path of the fork with the arc path of an A arm.
If you do use linkage how do you maintain the rigidity needed to support the lower part of the forks?
Very cool design if you can make it work. Definatly be some major weight savings.

 

[flatspeed]

Wouldn't this front suspension design require linkage in the A arm?
Without linkage I dont see how you could match the straight path of the fork with the arc path of an A arm.
If you do use linkage how do you maintain the rigidity needed to support the lower part of the forks?
Very cool design if you can make it work. Definatly be some major weight savings.

Speaking of A-Arms, I've been thinking about how they are more suited to a single ski machine than forks, as forks are designed for a wheel, and are unnecessary for a ski

A-arm Pros:
-lighter than forks (maybe?)
-potential for more travel
-more shock options including coils
-less static friction
-stronger, stiffer
-able to easily change single components if necessary (ie. revalved shock, bent a-arm etc)
-won't require an adapter spindle from fork to ski
-more options for moving rider c of g around

Cons:
-Doesn't look as cool (less like a bike)
-requires linkages, which take away from the direct steering feedback (plus slop in ball joints over time)
-arguably more complex
-stronger/stiffer may be a bad thing if it transmits impact force back to the frame, but the attach bolts could be designed as a fail point maybe, or the A-arms themselves?

 

[LoudHandle]

Wouldn't this front suspension design require linkage in the A arm?
Without linkage I dont see how you could match the straight path of the fork with the arc path of an A arm.
If you do use linkage how do you maintain the rigidity needed to support the lower part of the forks?
Very cool design if you can make it work. Definatly be some major weight savings.

To make the faux forks work with the lower A-arm link. It would need to pivot both directions at the triple clamp (think of a "U" joint).

Depending on material choices the faux forks may prove to be a real challenge to make them last a reasonable amount of time. Interesting concept for sure! Defiantly some out of the box conceptulization.

P.S. To date I've been unable to find any turning angles for any of the snow bikes. Closest I've seen is some rake and trail specs.

 

[roo]

To make the faux forks work with the lower A-arm link. It would need to pivot both directions at the triple clamp (think of a "U" joint).

Depending on material choices the faux forks may prove to be a real challenge to make them last a reasonable amount of time. Interesting concept for sure! Defiantly some out of the box conceptulization.

P.S. To date I've been unable to find any turning angles for any of the snow bikes. Closest I've seen is some rake and trail specs.

I moved a couple parts hawks yesterday to get access to start tearing them down. I can now get to my cr and ktm. Will get some angle measurements for you sometime this weekend.

 

[roo]

P.S. To date I've been unable to find any turning angles for any of the snow bikes. Closest I've seen is some rake and trail specs.[/QUOTE]

2002 ktm 520 mxc 36 deg. Each way
2000 cr 250 46 deg. Each way (i would say these numbers are +/-
1-2 deg., little harder to measure a bike than my hawk)
Maybe someone else could chime in about some newer bikes?

 

[Kealo]

Mine is tree fling ready.

https://www.snowest.com/forum/showthread.php?t=376728&page=2

How do you find your suspension? Looks like a sled uncoupled skid? I want to build a bike kit with all the sled parts i have and been wondering how sled suspension would performs vrs what bike kits are like.


Sent from my iPhone using Tapatalk

 

[Kaarlonen]

Wouldn't this front suspension design require linkage in the A arm?
Without linkage I dont see how you could match the straight path of the fork with the arc path of an A arm.
If you do use linkage how do you maintain the rigidity needed to support the lower part of the forks?
Very cool design if you can make it work. Definatly be some major weight savings.

Additional linkages or linear path is not needed.
My goal was to merge A-arm and fork suspension into one hybrid system, make it (maybe?)better and stroger and still make it look like a bike (hence the fork shape).
A-arm is there to take most of the impact forces and make the virtual steering "tube" legth or fork turn axis much longer compared to traditional fysical tube in motoframes. That longer distance between support points makes bending moment forces much smaller. With that you don't need beefy steering tube and bearing and upper frame = lighter structure and lower CoG.

Fork (as said before is not necessary to be shaped as a fork) is attached to the frame and A-arm with ball joints so the fork can move with the A-arm in arc path. A-arm is -10 deg in neutral position so ski pivot point direction during suspension travel is up and backwards in gently sloping arc. That fork tube/slider acts just like linear moving upper A-arm with infinite radius but you can steer the ski through the system without any additional joints between handlebar and ski and that is a good thing.
During suspension travel the steering angle becomes less steep which calms down steering feedback during big bumbs and hard landings. Front shock has rising rate instead of linear rate in normal forks.

 

[roo]

Additional linkages or linear path is not needed.
My goal was to merge A-arm and fork suspension into one hybrid system, make it (maybe?)better and stroger and still make it look like a bike (hence the fork shape).
A-arm is there to take most of the impact forces and make the virtual steering "tube" legth or fork turn axis much longer compared to traditional fysical tube in motoframes. That longer distance between support points makes bending moment forces much smaller. With that you don't need beefy steering tube and bearing and upper frame = lighter structure and lower CoG.

Fork (as said before is not necessary to be shaped as a fork) is attached to the frame and A-arm with ball joints so the fork can move with the A-arm in arc path. A-arm is -10 deg in neutral position so ski pivot point direction during suspension travel is up and backwards in gently sloping arc. That fork tube/slider acts just like linear moving upper A-arm with infinite radius but you can steer the ski through the system without any additional joints between handlebar and ski and that is a good thing.
During suspension travel the steering angle becomes less steep which calms down steering feedback during big bumbs and hard landings. Front shock has rising rate instead of linear rate in normal forks.

Now i am getting it!
Way easier to let someone explain a concept than just stair at a drawing and try to figure out how i would make it work.
I think the traditional fork set up will have to be sacrificed for real weight savings. Would love to see someone prove a better design.
Thanks

 

[LoudHandle]

For Kaarlonen's Front suspension design, I was thinking maybe even Mountain bike forks (gutted except the sliding bushings and some oil to keep them from wearing out too fast) but only found One (Risse Big Foot) that has 12" / 300mm of travel (and new they are pushing $2000). Kind of a shame to spend that much to gut them for just the coated tubes / bushings / and seals.

 

[Kaarlonen]

For Kaarlonen's Front suspension design, I was thinking maybe even Mountain bike forks (gutted except the sliding bushings and some oil to keep them from wearing out too fast) but only found One (Risse Big Foot) that has 12" / 300mm of travel (and new they are pushing $2000). Kind of a shame to spend that much to gut them for just the coated tubes / bushings / and seals.

Marzocchi super monster T had 300mm travel but it was more like a mx fork than mtb fork. It was stiff but heavy.
I think best solution would be to use one piece carbon/kevlar lower tubes with integrated spindle. Inside pair of plain simple off the shelf hydraulic cylinder slider bushings. Upper tubes 304ss welded to single crown.
Easy to make and needs little maintenance. I think there is no need for coated tubes and bushings or seals since there is no need to seal anything. Just put on some grease every now and then.