Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Can someone please explain how exactly the disc-o-matic works so I don't take mine apart to try to figure it out for myself?

Note: I know how to USE it, but am not quite sure how exactly it functions.

Hell, I understand DSGs, Auto trannys, SMGs, manuals, and CVTs more than I understand this.

Bump...Anyone?

Your transmission is a little more complex but the principle is the same as the one above.
At the top of the picture is a big pulley, driven by a V-Belt. There's a shaft back to the aluminum disc.

There's a friction disc (with a rubber coating) mounted so that by engaging and disengaging the clutch (you can see the lever sticking out) the friction disc  is moved into and out of contact with the drive disc.. When the transmission is engaged the rubber covered friction disc engages the drive disc. Power is transferred out the end of the splined pinion shaft to the drive mechanism that drives the axle and wheels.

The shifter on the handlebars moves this disc back and forth (mechanism not shown). At the outside (all the way to the right, as shown)  the diameter of the friction disc and drive disc are about the same and the pinion shaft spins pretty fast. That's 5th, or 4th, or zillionth, or top gear of however many forward speeds the marketing department decided.

If the friction disc is moved towards the center of the disc, the relative diameter of the driving disc is reduced. This yields a reduction in the rate of the pinion shaft, and the axle turns more slowly. That's first "gear"
The number of detents in the shift quadrant determines how many speeds you have.

This machine has a simple chain and gear reduction unit to drive a single axle that both wheels are pinned to. Other models differ in that they allow the two wheels to turn independently (like your LE). Some (DLE) have a differential, some unlock the wheels, and some can lock or unlock each drive wheel independently (like some Toros).

Most new blowers have "deadman" controls that require you to hold down a handle to engage the belt. Many larger units have more than one belt - one for the wheels, and one for the auger and impeller.

Now, if I gave you the diameter of the friction disk and the minimum and maximum distance from center that the friction disk can engage the drive disc, you could calculate the minimum and maximum theoretical gear ratios.

This place doesn't allow you to edit posts, so if this doesn't make sense somehow, there will have to be an addendum.....

The only thing to add is that if you move the friction wheel past the centre of the the disk you are now in reverse. It would be nice if there were faster reverse settings

So basically its a CVT(though not as complex as a toroidal or belt driven)  with slots for the shifter lever to click into...

Interesting. Does that rubber thingie ever have to be replaced?

So if i understand?  If  you go fowared faster you go slower in reverse?

Nope. It is equal both ways. However physically on the controls it doesnt allow you to pull it back far enough to go that "top speed" in reverse. With the speed mine goes I wouldnt want to back up that fast, especally with a device capable of crushing my face on one side(if it managed to drive all the way over me).

Garandman,  Thank you for the excellent description Disco-O-Matic.

Im sure if you wanted a faster reverse you could just cut out a new notch. ?

fatboy wrote:
If you look at the picture you'll see that the friction disc is located to the right  on the pinion. So  even if the assembly is shifted all the way to the left, the friction disc is still near the center of the hub. So it can't go too fast, even if you removed the shift gate altogether. There are some other mechanical detents and safeties built in that  I ignored, along with reverse - those are in Disc-O-Matic 102....

Yall have given me a great idea, though. I have a spare tractor unit. I'm going to call up a friend of mine at the Museum of Science in Boston and see if they'd like a display.

Wow, a reason to actually go to that goddamn museum(I have been over 1k times in my life).

Great description.  I always wondered how the tranny works in a blower. 

Yes, the rubber wheel does sometimes have to be replaced if it starts breaking apart. Here's a picture.

This was replaced by my friend Jim, who has a heated shop...I was going to do it, but it is too cold out for me...this is a summertime job....Jim did it for me yesterday....it is a friends snowblower.

Frank D.

faithfulFrank wrote:
That's ugly!

I sometimes wish that reverse was controlled by a mechanism that is separate from and independant of the speed control. That way you could have just as many forward as reverse speeds. Either that or a shift lever that moves further. There are a lot of times where I want to move the machine backwards and "R2" is just too slow If its a safety issue then you could make it so that to go faster than "R2" you have to make a concious effort of some sort. I.E. Move lever to right, push forward and then continue moving it right.

hi everyone,

can somebody explain this disc-o-matic system ?

do you need to stop the snowblower's moment in order to switch gears ?

thanks for any info.

Zippo.  Hi, there.  Yes, you do have to stop to change gears.  Same for reverse.  Only the Honda hydrostatic trannys allow you to shift as you keep moving.  But then, they don't have power steering.  Weird.

Update:  I wasn't so clear when I posted my first comment.  I was thinking of saving unneccesry wear on the rubber portion of the one disc.  You can shift while moving, but I'd prefer avoiding that possible extra wear.  It's certainly not a mechanical problem to change forward gears, or the reverse gears, but never go from forward to reverse, or vice versa, unless you stop beforehand.

coasteray wrote:
Actually you can shift on the fly. Just not from forward to reverse or vice versa or you could rupture the friction disk.

PK

in simple terms there are 2 disks one with a rubber outer surface and perpendicular to each other that contact and the farther out one moves the faster you go

coasteray wrote:
I wasn't so clear when I posted my first comment.  I was thinking of saving unneccessry wear on the rubber portion of the one disc.  You can shift while moving, but I'd prefer avoiding that possible extra wear.  It's certainly not a mechanical problem to change forward gears, or the reverse gears, but never go from forward to reverse, or vice versa, unless you stop beforehand.