Winter fun - Project “Freedom” 440cc 2 Stroke 1054 Snowmotractor

[Lee1977 6,658]

For speed remove the transmission (you will lose reverse).run a straight axle. Use a chain drive from the torque convertor to the rear axle. Don't know the gear up in your torque convertor set up, it's usually 3 to 1  to 1 to 1 wide open.

By being able to change sprockets you can get the gearing right for those large diameter rear tires.

I used these on minibikes and go karts. On the minibike with a K 91 Kohler I could get 45 MPH

They were adjustable from 3  to 8 HP engines.

[Pullstart 62,849]

I think I figured it out, based on a virtually direct drive transmission input pulley.  @8ntruck feel like double checking my aughts and gazintas?

Gear.   Start speed.   Top speed. 
1.             1.52.              12.47

2.             2.4.                19.65

3.             4.14.              33.86

R.            1.98.              16.17

 

I feel like I could do better.  

 

Edited January 13, 2023 by Pullstart

[Pullstart 62,849]

4 minutes ago, Pullstart said:

I feel like I could do better.  

If I run a 9.25” secondary shaft pulley for the transmission belt, I would achieve 50 mph plus or minus and have a reasonable 6.11 mph 3rd gear acceleration start speed, very similar to a stock tractor in 3rd gear.  Rock. On.  Time to look for a suitable 9,500 rpm rated 9.25” pulley with a 1” bore.

 

 

[Pullstart 62,849]

40 minutes ago, Lee1977 said:

Use a chain drive

This is likely simpler than I am thinking.  I did think of a chain drive live axle from a four wheeler of sorts, with suspension even.  For now, I want this next step to keep the wheel horse transmission. 
 

Any thoughts on a chain vs a belt being driven 9,500 rpm via a 9.25” pulley?  I will obviously have a safety guard in place on this one… keeping all my giblets to myself 

[Achto 27,570]

27 minutes ago, Pullstart said:

Any thoughts on a chain vs a belt being driven 9,500 rpm via a 9.25” pulley?

 

Motorcycles do this all the time with a chain.

 

I think that a #50 chain from the secondary shaft to the transmission input would be a wise choice and the route that I would take. Weld together hubs & sprockets would work for this application.

https://www.surpluscenter.com/Power-Transmission/Sprockets/Weld-On-Sprocket-Hubs/

 

One other thing that I would strongly consider is braking. Maybe replace the hub & band brake with a disc brake set up like @Wild Bill 633 is doing on his build.

 

 

Edited January 13, 2023 by Achto

[Wild Bill 633 845]

The circumference of a 9.25" diameter pulley is 9.25 in. * 3.1415 (PI) = 29.06 in.

9500 rev/min * 29.06 in./rev * ft/12 in. = 23,006 FPM

 

V-belt drives are used in the 2500-7000 FPM. A speed of 4000 FPM is generally ideal. Chain drives are typically used at lower speeds with higher torques. Most commercially available sheaves are cast iron, which need to be balanced above 5000 FPM, and limited to 6500 FPM. Steel pulleys are good up to 10,000 FPM.

 

On my build:

1) Engine/CVT driver 3750 RPM

2) CVT ratio 0.53:1 (overdrive)

3) 1" diameter jackshaft with CVT driven and 3.75" OD v-belt drive pulley 7075 RPM /6946 FPM

4) Jackshaft mounted in 1" Seal Master high speed pillow blocks (McMaster-Carr P/N 2722T34) max. speed 9000 RPM

5) 3.75" OD v-belt driven pulley 1:1 ratio

6) Transaxle input speed 7075 RPM

7) 8-speed transaxle 3rd hi ratio 24.6:1

8) Tire circumference 69.9"

9) Max. speed 19.0 MPH calculated with no losses.

 

Edited January 14, 2023 by Wild Bill 633

[8ntruck 6,999]

Without putting pencil to paper myself, your ooghts and gizintas look right. 

 

Might want to back check yourself by working the problem backwards.  Start with the tire rpm needed for 50 mph and work through the high gear ratio to transmission input shaft, transmission input to jackshaft ratio and the 1.167 converter ratio to see if you come up with an 8000 rpm crank speed.

[Pullstart 62,849]

5 hours ago, Achto said:

Motorcycles do this all the time with a chain.

 

1 hour ago, Wild Bill 633 said:

The circumference of a 9.25" diameter pulley is 9.25 in. * 3.1415 (PI) = 29.06 in.

9500 rev/min * 29.06 in./rev * ft/12 in. = 23,006 FPM

 

V-belt drives are used in the 2500-7000 FPM. A speed of 4000 FPM is generally ideal. Chain drives are typically used at lower speeds with higher torques. Most commercially available sheaves are cast iron, which need to be balanced above 5000 FPM, and limited to 6500 FPM. Steel pulleys are good up to 10,000 FPM.

 

Dan rethinking this, motorcycle engines might spin that fast, but through a transmission they likely never run that fast at the chain.  Snowmobiles have a final drive chain, after the secondary clutch.  They surely don’t drive a 9” sprocket 

[Wild Bill 633 845]

@Pullstart

Added a column to my spreadsheet for speed calculations for your Snowmotractor and the results are as follows.

1) Engine, 7750 RPM

2) CVT ratio, 6" driven/7" driver = 0.86:1 overdrive

3) Jackshaft, 9042 RPM, pillow blocks max. 9000 RPM "limiting factor"

4) Jackshaft v-belt drive pulley, 3.75" OD, 8876 FPM, >6500 FPM, S/A Browning BK36X1 "except machined out of steel"

5) Transaxle input v-belt driven pulley, 3.75" OD, 9042 RPM, >6500 FPM, S/A Browning 1B34SH "except made out of steel" and Dodge QD SH 5/8 bushing P/N 120347 for 5/8" shaft. See pictures.

6) Transaxle 3rd gear ratio 24.6:1

7) 30" tire, 32.8 MPH

 

PM sent.

 

Edited January 14, 2023 by Wild Bill 633

[Achto 27,570]

3 hours ago, Pullstart said:

Dan rethinking this, motorcycle engines might spin that fast, but through a transmission they likely never run that fast at the chain.  Snowmobiles have a final drive chain, after the secondary clutch.  They surely don’t drive a 9” sprocket 

 

Crotch rocket engine can reach 15,000 rpms. This may not happen in high gear which would be 1 to 1 drive at the tranny sprocket but this would still exceed the rpms of a snowmobile engine in even one gear down from high gear. If you are running a 9" sprocket on the secondary shaft, what size sprocket would you plan on running on the tranny? 

[WHX?? 48,815]

Let's not give him any ideas on speed Dan... just sayin  

[Pullstart 62,849]

1 hour ago, Achto said:

If you are running a 9" sprocket on the secondary shaft, what size sprocket would you plan on running on the tranny? 

6-1/4” was the plan for 50 mph. 
 

1 hour ago, Wild Bill 633 said:

PM sent.

 

Thanks Bill, I’ll be in contact soon!  Gotta go to the big city and pick up the in laws from their Caribbean islands trip!

[Achto 27,570]

8 minutes ago, Pullstart said:

6-1/4” was the plan for 50 mph. 

 

21 tooth on the secondary shaft and a 14 tooth on the tranny would equal out about the same. 

[Wild Bill 633 845]

@Pullstart

Engine CVT drive speed 8000 RPM

CVT ratio 0.86:1

CVT driven speed 9333 RPM

 

Tires 30" dia. 94.25" circumference

at 50 MPH, axle speed 560 RPM

9333 RPM / 560 RPM = 16.66:1 speed reduction

 

Suggestion: make the driveline similar to the snowmobile.

 

[Pullstart 62,849]

47 minutes ago, Wild Bill 633 said:

@Pullstart

Engine CVT drive speed 8000 RPM

CVT ratio 0.86:1

CVT driven speed 9333 RPM

 

Tires 30" dia. 94.25" circumference

at 50 MPH, axle speed 560 RPM

9333 RPM / 560 RPM = 16.66:1 speed reduction

 

Suggestion: make the driveline similar to the snowmobile.

 

I came up with a 16.66:1 number earlier as well.  If I run my secondary to a third-ary, I think I can make it work. Question on ratios… if 8 do the math, I can likely answer my own question.  If I ran a 3.75 to a 7, that would be 2:1. After that, am I looking for 8.33:1?

[Pullstart 62,849]

Here I am, thinking about gear reductions and whatnots, and this picture popped in my head.  This is one of the FL airports, when we were on our way home from some adventure…

3250 rpm electric motor, spinning the fan about 40 rpm

[SylvanLakeWH 25,555]

I thought that was a Florida mosquito st first...

 

[Pullstart 62,849]

I’m trying, thinking, brainstorming.  @Wild Bill 633‘S hot rod picture of the brake rotor made me wonder about running that as a transmission input.

 

I believe this is the gear setup from the brake shaft back.  @stevasaurus or @ebinmaine you out there?  You guys have been in there a time or two.

 

 

It so, the first shaft to the second is 14:44 and the second shaft to the differential is 11:43.

 

Could this help me?  I have no idea right now.  

 

[Pullstart 62,849]

I believe this video confirms my thoughts on gear shaft configuration.  Now to see if it can help me at all.

 

 

[Pullstart 62,849]

This gets me 12.29:1 I’ll have the secondary shaft running to the left side of the Snowmotractor, spinning the correct way to drive the brake drum.  I could gut the transmission for less rotating mass if I want to.  I could make small pulley adjustments to get my 16.6:1 for a 50 mph top speed.

[Pullstart 62,849]

With a 3.75” secondary shaft pulley and 2.75” transmission brake shaft pulley, I’m thinking we found 50 mph!

 

 

Edited January 14, 2023 by Pullstart

[SylvanLakeWH 25,555]

50 mph

 

 

Queue the ...

 

Boy... when's you gonna learn ...???

 

[wallfish 16,995]

1 hour ago, Pullstart said:

With a 3.75” secondary shaft pulley and 2.75” transmission brake shaft pulley,

I'm think'n the 8 speed trans brake shaft spins forward, not back like the input shaft does.

It's been about 10 years since playing with using the brake shaft to spin one but I remember using an old snowblower (62 round type) shaft that has gears in a box to reverse the direction. My memory does suck now so I could be wrong. Can't remember what I had for dinner either! LoL

Also, with 3 sets of gears like you showed in the video, the last gear will be spinning the same direction as the first gear does with the center gear going the opposite direction of the other two

 

Edited January 15, 2023 by wallfish

[Pullstart 62,849]

5 minutes ago, wallfish said:

I'm think'n the 8 speed trans brake shaft spins forward, not back like the input shaft does.

It's been about 10 years since playing with using the brake shaft to spin one but I remember using an old snowblower (62 round type) shaft that has gears in a box to reverse the direction. My memory does suck now so I could be wrong. Can't remember what I had for dinner either! LoL

Also, with 3 sets of gears like you showed in the video, the last gear will be spinning the same direction as the first gear does with the center gear going the opposite direction of the other two

I fought with myself trying to figure this out.  I thought how you did, then I proved myself wrong, but proved yourself right!  Dang.  I was so close!

 

what to do what to do.  Snow blowers’ chains run the drive pulley shaft on a sprocket and run the back side of the chain to the auger.  Thoughts on that here?  Somewhere?

[Pullstart 62,849]

9 minutes ago, wallfish said:

opposite

maybe I should spin the engine around again to run like a sled!