Andrew Pollack's Blog

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The Completed Snowthrower Rebuilding Project

By Andrew Pollack on 09/16/2008 at 10:52 AM EDT


I find it much easier to work on and repair a snow thrower on warm September evenings and weekends than on cold February mornings when I'm trying to get the car out. This year will be the 13th year of service for this MTD 8hp snow thrower. MTD products fill the lower cost market niche in equipment but my experience with their products has always been extremely positive. There are more expensive machines that are built to supposedly last longer -- and maybe they would. Would they last twice as long? They cost twice as much so that's the real question to ask.

Before

After



I've also found MTD products to be very well engineered. One of the ways they save money when they build them is to use very simple drive mechanisms. These are ingeniously built, however, and end up being much easier to keep working. The mower uses a "Constant Velocity" transmission based on pulleys and belts that change ratio based on speed in a smooth curve. This is extremely efficient, and some day we'll all have these in our cars. For now, they're not strong enough to handle most cars (the Subaru Justy used one, but that was more a go-cart than a car).

This snow thrower also uses a drive mechanism that is pure genius. The motor turns a belt that makes a large, flat plate spin around like a record. Above the plate is a rubber ringed wheel which contacts the spinning plate on its flat surface a right angle. When the plate turns, it turns the wheel much in the same way a pair of gears set at right angles would mesh. Unlike gears, however, the rubber wheel can make contact anywhere on the spinning plate -- not just at the edge. All the gearshift does is move the rubber coated disk further out to the edge of the plate where it will spin faster, or closer in toward the center where it spins slower. Reverse is accomplished by moving the plate even further -- across the mid point so that it contacts the plate spinning the other way. The rubber ringed disk is around an axle with a gear at its end. The wheel can move side to side, but always along this axle. When the wheel spins it turns the axle, which drives the gear that makes the wheels go. Its brilliantly simple and the only two wear parts in the system are the belt that turns the spinning plate, and the rubber ring around the drive disk. Both are easily replaced and readily available.

You can see blown up diagrams of the whole mechanism here: http://www.m-and-d.com/pdfs/MTD/E640F_E660F_E6C0F_E660G.pdf

This unit is, as I said, about to see its 13th service year. In some Maine winters, that can mean being used thirty or forty times, often handling six to eight inches of heavy snow. The scoop was bent and rusted. The scraper bar on the bottom had worn half away and had exposed the bolts which hold it to the scoop. Those bolts were half to fully worn away themselves. The bushings on the auger blades were worn, the blades rusty and long since scraped clear of paint.

As you can see from the pictures below, I tore the unit down and cleaned the old paint off. I used a wire brush to clean as much rust off as possible, and stripped the paint to bare metal. Parts for MTD products are very easily found. I downloaded a parts diagram showing a blow-up assembly plan with labeled part numbers and used that to order a new scraper blade, new bushings for the auger blades, a new bearing for the auger shaft, new belts, and new springs for the controls and idler pulleys. Every bolt, nut, and washer I removed was replaced with a new one from the local hardware store.

The scoop was heated with a propane torch where it was bent and a five pound hammer used to bang it back into shape. The crease at the leading edge was done by placing that edge of the scoop against a piece of angle iron and hammering against that as an edge. Anywhere rust could be found was prepped with rust-reformer (available at NAPA and other such places) then the unit was brushed and sanded again before paint. I used seven cans of Rustoleum "Farm Implement and Tool" paint in the color "International Red" over the course of several days. The few bolts that weren't replaced due to being part of the chassis itself were cleaned using the appropriate sized thread cutting die then treated to prevent rust.

For the screw gear at the front of the auger, MTD recommends 1.5oz of Alvania bearing grease. Though I couldn't find that particular grease (and didn't want to order it) NAPA was able to call their "Valvoline Help Desk" and quickly cross reference it to a high grade synthetic bearing grease they carry. The grease is fantastic stuff. Its red, which is a bit odd, but seems to be almost totally impervious to washout. In fact, I had a really hard time getting the stuff off my hands. Even the degreasing, abrasive, mechanics soap I used wouldn't touch it. I also used this grease to coat some of the hidden parts that tend to rub as levers are pulled and so forth, and any places where newly painted parts were joined by bolts to prevent the paint from bonding there.

When I finished, the unit started right up -- I hadn't touched the reliable Tecumseh 8hp motor other than to replace the spark plug. When I went to test it, I couldn't tell if the auger was even moving. I had to tie off the lever that operates the auger and walk around the front to make sure it was working. The movement of the auger was wonderfully smooth and silent.

Click for the full sized image



There are  - loading -  comments....

re: The Completed Snowthrower Rebuilding ProjectBy Timothy Briley on 09/16/2008 at 12:52 PM EDT
I've gotta me one of those!

Oh wait. I live in Florida.

Nevermind.

BTW, we met at Lotusphere. And I'm still reading every post on your blog. Keep
up the good work.
re: The Completed Snowthrower Rebuilding ProjectBy David Schaffer on 09/16/2008 at 02:46 PM EDT
How ambitious!

I think I have the same machine. Around October I check to see that the pins
aren't broken and that it will start and has oil. That's about it for
maintenance around here.
re: The Completed Snowthrower Rebuilding ProjectBy Lars Berntrop-Bos on 09/17/2008 at 03:25 AM EDT
Actually, there is a Dutch invention called the Van Doorne transmission, which
uses a belt with steel sliders on which IS strong enough. One day...
re: The Completed Snowthrower Rebuilding ProjectBy Graham Richards on 09/17/2008 at 02:18 PM EDT
Audi have had a CVT available for several years now. I've been driving an A4
with this since 2002, and absolutely love it.

http://www.audiworld.com/news/99/multitronic/content.shtml
re: The Completed Snowthrower Rebuilding ProjectBy Craig Wiseman on 09/20/2008 at 09:06 AM EDT
Throw? Snow?
What? Since I was born, I don't think I've seen 6-8 inches fall on my home. Not
per year... in total...

Neat article, though.
cpw...
re: The Completed Snowthrower Rebuilding ProjectBy Craig Wiseman on 09/20/2008 at 10:11 AM EDT
OTOH, I do have 5500w generator that's seen a boat load of use lately.

So, I guess we all have our crosses.
re: The Completed Snowthrower Rebuilding ProjectBy Scott on 09/23/2008 at 10:43 AM EDT
I agree 100% with your MTD performance, design simplicity and overall value
observations. I am a long time user of older Ariens two stage blowers and
have performed similar overalls twice on a 1972 Ariens 7-24. Recently my
brother in-law moved and gave me his old MTD 8-24. I remember using it once
was impressed how far it threw the snow (also noted my neighboru2019s MTD 8-28
has the same results) so I decide to rebuild this unit. Working on the MTD was
much easier than Ariens, especially the disk drive area. The MTD utilizes
dual PTOu2019s, which enables the blower fan speed to run more independently of
the wheel drive speed.
Long story short, my MTD axle and drive bushings were toast, but the drive disk
had plenty rubber. As you noted these parts are cheap to replace. However,
the housing was extremely rusted, banged up and worn away (skids and scraper
bar gone!). This is where one appreciates the Ariens units for the overall
material thickness is twice and the blower housing retains its shape. Also the
paint process/finish is superior on Ariens which does an excellent job of
preventing rust. I was just about to give the MTD housing the same treatment
as you did, but then found on Craigu2019s list a MTD 10-24 about 8 years old
with a blown motor for $150 in excellent condition. It was almost a
therapeutic process swapping the motors. This housing also needed skids and
scraper bar which cost $35 in total.
The problem I now have is still being emotional attached to the robust Ariens
7-24 housing! The chute design is old and will clog with heavy end of driveway
slush. It does not have dead man auger control option and it lacks a headlight
(engine missing generator output). In addition I have the reputation to keep
with all the neighbors as the frugal fool with old Ariens.
re: The Completed Snowthrower Rebuilding ProjectBy Bill White on 10/18/2008 at 03:49 PM EDT
This is a work of extreme genius -- the blog, I mean. I have precisely the
same MTD thrower, of exactly the same age. My wife is even from Maine! -- but
we're in Connecticut.

Your blog and large images have helped me immensely today, tearing down the
thrower and given me confidence that I can reassemble it (the important part).

I'm going to order belts, scape plate, skid shoes, etc. And I need a new
recoil starter rope - if the electric starter unit blows, no thrower - that can
be a safety issue in winter, if we're stuck in the driveway - wife is a nurse.

So thanks for this, and I'll keep you posted!

-- Bill


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