The Autobroom!

It looked good on paper

Introduction

I needed to clean my roof. 24hrs later, I had something that worked as designed and my roof still needed cleaningSome blatant foreshadowing.

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My house is surrounded by trees, which is a good thing, but those trees drop a lot of pine needles, seed pods, and more on my roof. Also, a quarter of my roof is north-facing & shaded, which in the PNW means moss.

The messy roof, and rake-on-a-pole.
The messy roof, and rake-on-a-pole.

So, not only do I have to clean the gutters every month, I have to attach a lawn rake to a long poleIt’s an old pool-cleaning pole, I removed the net and the rake handle now fits perfectly in the end.

and clean my roof a few times a year by “raking” my roof from the ground.

My house is a single-story ranch, which is what makes this possible, as the roof is too steepEven the pros don’t like it. I use a climbing harness and rope to secure myself when I do have to get on the roof.

to walk on.

Inspiration

As I prepared for yet another (not) fun afternoon of raking my roof, I thought about how I could clean the roof more efficiently. And obviously, power tools must be part of the solution.

The roof is covered in asphalt shingles, which is basically tar paper & gravel. You can’t clean it too aggressively because you don’t want to strip all the gravel off, nor tear the shingle.

Leaf blowers can remove loose stuff like needles, but what about moss? Moss requires just the right touch to scrape it off the shingles – leaf blowers would either not work, or also take the shingles off.

Instead, what about a push-broom? They are available with stiff bristles, and are wide to cover a lot of area quickly. And if you had two push-broom heads rotating on a horizontal axleLike the big front-brush on a street-sweeper.

it would be like an infinite broom…an autobroom!

Construction

I immediately had a plan in my head. After a trip to Home Depot and Harbor Freight, and raiding my spare parts bin, I had all the parts I needed.

Modifying the drill

The first step was to remove the drill handle from the body, so I could attach the drill to the brush but control it from the ground.

Taking the drill apart.
Taking the drill apart.

I had some leftover speaker wire the house, it’s 16/2This is always confusing. 16/2 usually means 2-conductor wire and ground. But this is 2-conductor wire (black & red) without ground. What should it be called?

AWG copper wire and plenty big enough to handle the electrical load for the remote handle.

Drill with remote handle.
Drill with remote handle.

Attaching the brushes

The push-broom brushes needed a little modification to be attached to the axle - they had a bump where the broom handle inserts. After trimming that away, it was quick to drill some bolt holes and attach them.

Removing the bump.
Removing the bump.
Bolting it all together.
Bolting it all together.
It looks like something from the car wash.
It looks like something from the car wash.

Building the frame

Next up, raiding the scrap-wood pile. There’s nothing too fancy here, it’s all 2x4 lumber, plywood, and random hardware. It’s much easier to “measure” by laying things together and marking them than trying to calculate offsets, etc.

Fitting the axle.
Fitting the axle.

The pulley was made by pinning a square piece of plywood on a table-saw jig and rotating it against the blade until all the corners were cut offBecause circles are just squares without corners.

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Pulley ready to attach.
Pulley ready to attach.

How do you attach a round-ish object to a flat board? With lots of zip-ties! You can also see the second, smaller pulley mounted on the drillRaise your hand if you’re concerned about the lever force that will be applied to the small, unsupported pulley on the end of the drill.

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The pulley ratio was not calculated – I just knew it needed to be slowed down. I wasn’t worried because the remote handle has a variable speed trigger for controlling the brush speed.

It’s ugly but it works.
It’s ugly but it works.

The link belt is a wonderful invention. Not only does it allow you to break the belt to thread it through holes, you can easily re-size it for the application at hand.

The drill is mounted to a hinged board, the threaded rod adjusts the board angle to apply tension to the link belt.

Tensioned link belt.
Tensioned link belt.

Caster wheels are added to the frame so it can be pushed around on the roof - two straight casters in the back, and one swivel caster in the front to help with steering.

The front swivel caster is mounted on a hinged board so the height of the brush can be adjusted, the small plywood board on the side locksIt’s just screwed into place, nothing fancy. To adjust the brush height, it’s un-screwed, angle adjusted, and then re-screwed in new holes, because you can’t re-screw too close to the old hole.

the hinge position.

Now with wheels.
Now with wheels.

Reinforcing the drill

After some testing, the drill mounted with zip-ties was entirely insufficientWho’s surprised that zip-ties were not the right solution?

to support the required belt tension. The pulley on the drill also needed additional support.

The drill mount was rebuilt with a pulley support and a solid u-bolt to mount the drill.

Much better than zip-ties.
Much better than zip-ties.

Attaching the handle

The handle was made by re-using the original broom handles to build a triangle frame, then attached to a 10’ copper pipe.

Mounting brackets were quickly fabricated from the scrap pile and attached.

Triangles are strong.
Triangles are strong.
More scrap from the bin.
More scrap from the bin.

Final Result

With everything finally assembled the remote handle was re-connected and the brushes powered on.

The final form.
The final form.

I gave it try on the driveway where I had a thick carpet of pine needles, and it worked wonderfully!

A clean swath through the needles.
A clean swath through the needles.

The next day I tried to clean the roof with it…and failed. There were two fatal flaws:

  1. It was too heavyThat was literally the first thing my father said to me when I described the project: “It’s will be too heavy to use on the roof.”

    for a person to attempt to maneuver on the roof via a long pole held overhead from the ground.
  2. Due to the roof angle, not enough weightWhich is ironic, given #1.

    was transferred to the brush. Instead of brushing the shingles effectively, it just bounced around in a terrifying manner.

And so the autobroom was disassembled and the spare parts bin is now a little bit richer.

Instead, a roof & gutter cleaning companyLet the professionals do their job, they know what they’re doing.

comes out every month. It’s a little pricey, but worth it for the hours of time I save by not doing it myself.