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

I never realized that by explaining how the friction wheel drive on another thread would cause such feelings of inadequacy in one poster that he felt compelled to pretend I had personally attacked him, which was never my intention.  But now that this has come to be a subject worthy of discussion, let's explore the comparison.   Most snowblowers of the two stage variety use the very simple, easy to understand friction wheel drive to propel them.  Here then is the system explained so we all can begin with a clean slate. 

  The snowblower engine drive shaft will have a pully on it to drive a Vee belt that is attached at the other end to a 'Drive Plate'.  So long as the engine is running, the plate is spinning thanks to that belt.   The wheels or tracks of the snowblower are connected to the drive system through a rubber faced friction wheel that rides at right angle to that 'Drive Plate', and the shaft the 'rubber faced friction wheel' rides on is one the rubber wheel can slide along from one side to the other.  That sliding motion then positions the rubber tire like friction wheel on the 'Drive Plate' depending on where you place it.  This is done with the cable running from the notched speed change lever on the operators console of the machine.  When you, the operator, squeezes the handle that engages the drive you are lifting that engine driven 'Drive Plate' into contact with the rubber faced 'Friction Wheel' and if the rubber is in good condition, and properly adjusted , it makes contact with the drive plate and the snowblower will begin to move.  How fast or whether you move forward or reverse is dependent upon that speed control that usually has something like 6 forward speed noitches, and two reverse.  That cable running to the friction wheel will allow it to ride across the drive plate at the center, for low speed, closer to the edge for high speeds, and even on the other side of the drive plate's center to make the friction wheel spin the opposite direction.  This puts the machine in reverse.  This then is what plays the role of a transmission on all 'Friction Wheel Drive' snowblowers.

The problem is that if the drive belt slips, the machine will not move.  If the rubber tire like friction wheel becomes hard and glazed, it will not properly grip the flat metal Drive plate, and you again, won't move.  In fact if the plate surface is slick from wear, or the friction wheel rubber is worn down, like when the tire on your car becomes bald it will again not properly contact the drive plate and transfer the engines power to those tracks or tires. Usually before this occurs you get a period of use when the machine requires the operator, You, to push it when it encounters greater resistance.  So it may move forward until it has to push itself into that heavy salt laden "end of the Driveway" pile, and then the friction wheels reduced 'Friction' ability causes it to spin no longer as the drive plate becomes polished from rubbing against the immobile rubber surface.  Here you have two options, first is you shove the 200 pound machine into the snow, or second, you stop, take it back into the garage where you better have the new friction wheel rubber and the tools and know how to replace the worn one that has rendered your snowblower useless.  This happens to such machines as a result of normal use, and depending upon how much wear that friction wheel suffers from the normal use of the machine.  Thus a snowblower moving light powder all the time will go much longer than the same machine used to throw, and push itself into wet heavy snow which wears the friction wheel more, and thus wears it out much faster.  If you happen to live in a climate where the snow is often wet and heavy, rather trhan light and fluffy powder, you should evalutae your ability to deal with this maintenance item.  Your owners manual will supply the repair procedure for this in most cases, as well as a parts diagram so you can order, and have on hand the necessary new rubber tire for that friction wheel.   The manufacturer supplys that information precisely because they recognize the fact that your snowblower will, at some point, require this work be done.  I personally understand all this from about ten years owning an Ariens Snowblower, followed by 15 years with an MTD built Sears Craftsman snowblower, both with the same friction wheel drive mechanism.    Where I live in southeastern New York State, wet heavy snow is the rule, light fluffy powder is the exception.  This resulted in having to change these friction wheel rubbers about every two years on average, so my next new snowblower choice eliminated the problem entirely, albeit at some considerable cost.

The alternative system employs an actual 'Transmission'.  My John Deere Lawn Tractor ( X-300R) has such a transmission, and it has been problem free for many years.  So I paid as much for a new Honda, hydrostatic Transmission Driven snowblower (HS 928 TAS) as I paid for that John Deere tractor.  The extra cost to me was worth it. 

Now I do not tell everyone to buy the same machine I did, or even to avoid the friction wheel drive system common to most other snowblowers.  I simply think that BEFORE you spend the money on that new snowblower you know what you are buying.  The manufacturers, store clerks, and even Consumer Reports magazine will NOT tell you, as I just did, the Reality of owning those simple less expensive drive systems.   By reading this you now understand : A)- How the thing works, B)- What To expect, and WHY, and C) - You now can buy based on an Informed Choice without discovering the hard way what will happen from normal use to your snowblower. 

Well, since the thread was resurrected I wonder if a couple of misunderstandings of the friction drive might be up for discussion. 

I too have had no problems with the friction drive on my 1982 Toro 724.  I inherited it from my brother when he moved to AUS.  It's spent its whole working life in West Michigan near Muskegon.  I'd say we get snow in all varieties and have had some real doozies in addition, of course, to many sparse years in between.   But it's the original rubber drive in there.  This clutch has been maintained well and inspected yearly and looks to me like it was easily intended to last the life of the machine.  My blower is in near-new condition and well past its likely intended lifespan. Clutch amazingly shows little signs of wear.   I've greased, oiled, inspected, replaced parts 95 percent of the time with off-shelf items from belt and bearing suppliers (not 2x to 3x more expensive OEM),  repainted and tig welded when needed.  It's still in such good shape that last fall I replaced the still fine but tiring 7hp Tecumseh with an 11hp OHV Techumseh for 150 dollars shipped to the door.

The clutch's  robustness and power to the wheels have always defied intuition for me.  A simple rubber wheel held against a smooth steel disc driving a heavy machine into the snow?  There must be more to this.  So I stared at it one evening when I was in there greasing all the shaft bushings.  Sorry if this is actually common knowledge but I saw no reference to the real mechanics of this described in the thread.

The spring, unlike as described here and generally understood, does not hold the rubber to the disc.  In fact it pulls in the other direction!  Hmm.  If the spring is too tight (not likely is using an OEM) it will only serve to make engaging the drive at the handle grip more difficult, but will have zero effect on the pressure/engagement of the rubber against the disc.  The spring in question only serves to DISengage the drive, not hold the rubber to the disc.  So what is holding the rubber to the disc?  Not just the handlebar grip since that would make it very difficult to hold such strong engagement by the hand alone and would be tiresome.  The answer is a pretty elegant camming action and obvious if you look closely.

My Toro rotates the rubber drive wheel against the disc.  Some other designs bring the steel drive disc against the rubber wheel.  Both work on a similar principle of jambing the faces together with a camming action. 

There must be better engineering terms to describe this.  Sorry I'm not an engineer.  The rubber clad wheel is cammed about its axis.  I'm not saying, of course, that the rubber clad wheel rotates eccentrically.... only secondarily about its axis. When that assembly is rotated toward the steel drive disc the rubber engages the disc at a point just above the centerline shortest distance between the disc face and the rubber clad wheels' eccentric axis. At this point what you are doing at the handlegrip is pulling against the clutch drive spring. The clutch drive spring is keeping the rubber wheel away from the disc, not against it.  Once you've overcome the spring resistance with the handlegrip to bring the rubber to touch the spinning drive disc it grabs the rubber wheel, and using the rubber wheels' resistance (since it's mechanically static and linked to the wheels)  it drives the clutching faces a few degrees beyond the shortest distance between them determined by the rubber wheels' axis. This  jambs the rubber wheel against the steel disc with pressure far greater than could be accomplished with a spring alone.  Once in this position the only way to unjamb the rubber drive from disc is to release the handlebar grip and allow the strong clutch spring to pull the rubber back and out of its jamb against the disc. 

Anyone noticed that when this spring breaks or goes waaay too weak it does not result in a no-drive or weak drive situation?  If the spring breaks the clutch will remain engaged in the gear it was in and you can't stop the beast.   There is no longer any spring to pull the rubber wheel away from the drive disc.  Another indication that this jambing/camming action is at work is that reverse is significantly less powerful than the forward settings.  The jambing design is, in reverse, working opposite of its intended design.  In reverse the only pressure applied to clutching faces is what you provide with the handlegrip since the disc is now rotating up against the rubber instead of downward and no jambing takes place.  The handlegrip linkage itself is levered at a point only a degree or so before it would jamb (and then render the clutch return spring useless in pulling it back) so it provides sufficient ease on the hand when holding it in reverse for a short while.


If the spring has nothing to do with the pressure of the rubber clad wheel against the drive disc I wonder what else might be at play when some notice that the drive is slipping.  It's easy to see how grease might be a culprit if it's not applied carefully.  Once slippage is induced over a period of time glazing would occur.  Nothing to do but sand it smooth and try again with a clean setup.  I don't believe that the steel face can become "too smooth",  The smoother the better as long as it remains dry and oil free.  Smooth = less wear on the rubber.  In a well 'jambed' state a rough surface should provide no better friction.  Rubber formulation and local climate are probably the worst factors. living near a corrosive salty ocean or running the blower on heavily salted surfaces would affect the life of all components, metal or rubber.  A poorly forumulated OEM rubber would crack and break down much faster than a superior one.

What might be interesting (just a little) is the relative efficiency of the friction vs hydrostatic. No doubt the hydrostatic is higher, and (i think) usually incorporates some form of differential to the drive wheels which must be a very nice addition for ease of use.  All totalled I would personally opt for the friction drive again if given the choice between two identical models (just for sake of comparison.... i doubt that choice exists between two otherwise alike blowers).   The friction drive has proven itself to me, and I'm confident enough of my mechanical skills to fix it cheaply if it fails for whatever reason (unlike hydrostatic which would likely be an expensive fix or total replacement),

Sorry about all that if it's confusing, or worse, foolishly overstating the obvious for most here.   An engineer might have explained that in one paragraph.  

My 2 cents. I happen to be in the market for a 2 stage snow blower and doing my online research. Glad I came across this forum. I am making comparisons with Ariens, Cub Cadet and Toro where I noticed the various names they called their drive systems. Ariens calls theirs Disc-O-Matic and the others simply said self-propelled. The engineer that I am got me curious so I googled the terms. I realized then that this is the same old technology used in some lawn tractors. It may be reliable but it IS antiquated. I am quite surprised that manufacturers have not retooled and just made hydrostatic a standard instead of asking a premium price for them. When I bought my JD lawn tractor years ago, my main criteria was to get a hydro drive to replace my gear driven Simplicity. Needless to say I never looked back. The fact the mfrs don't go in to too much detail about the disc drives tells me they are holding back very important information for a consumer to know. I was leaning towards an Ariens at first as I do have a 5hp paddle push type Ariens blower and have been happy with it. They do make a hydro blower but appears to be more than double the price of a disc drive. It looks like I need to do some in depth shopping to see what I can get out there that suits my budget without compromising.