NotTaR of small Gasoline Engines and Rotary Lawn Mowers : Another reason not to mow rocks!        
 Copyright © 1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying. I may be contacted via the Sci.Electronics.Repair FAQ (www.repairfaq.org) Email Links Page.

     << Crankshaft-friendly blade.. |  Index  | Rod disasters - or why th.. >>

Another reason not to mow rocks!

(From: Forbes Family (fbsfam@clear.net.nz).)

I have recently purchased a new rotary lawn mower and appear to have started wrecking it in the first two weeks of use! Problem is, my property has lawns that run alongside a gravel driveway, and its often very hard to guarantee there are no stones lying in the grass before you start mowing. Not surprisingly I often hit small stones. These usually cause no harm, but today some teenagers were mowing my lawns and hit a real monster that measured approximately three inches by two by one, and weighed more than half a pound! Although the mower seems still to work OK, the impact has created a three inch long tear in the mower's cast aluminum body. Not a nice thing to have happen to a new machine!

Despite the stone's size, I was surprised at the size of the resulting tear in mower's more than 1/4 inch thick aluminum casing. I hadn't imagined a rotary mower blade powered by a 5 HP Briggs and Stratton motor could produce such force!

It would be interesting to hear from others who have survived similar experiences and to get an idea from any budding engineers on whether its perfectly reasonable for a stone this size to do such damage to the body of my mower - or whether it's more likely the body casting had a manufacturing defect that made it split prematurely?