I was standing on the train last week next to two ladies who were discussing the merits of their new hedgecutters. Both, however, agreed that their trimmers were so heavy that they had to get their husbands to use them or call in a gardener, one also complained that the noise was so terrible that even the builders extending their new kitchen (in their 'old' house of 23 years) had complained to them.
It struck me that these problems could be allieviated by the use of a miniature turboshaft* engine rather than the more conventional 2-stroke engine currently fitted.This also prevents problems associated with battery oparated ones (eg. only having a few batteries and having to wait for them to charge rather than being able to top up with more fuel without the wait for power to be put into the fuel, or that batteries run flat gradually).
The advantages include the high power to weight ratio compared to reciprocating engines (although I am stuggling to find data to compare the two), relatively small size and the inherent coolness of having a jet engine in your hedgecutter/chainsaw/strimmer/[insert power-tool here].
Disadvantages of course include the very hot exhaust stream and relatively high maintenance.
I mentioned that sound was a problem too: I believe that the sound of a jet engine is more of a loud high-pitched whine than the relatively low pitched 'brrrrrrrrrr' of a reciprocating engine and would suggest that current ear protection, which generally absorbs high frequencies best, should be better at reducing the sound of the turboshaft garden tools than those powered by the latter means. Anyone so far away that the sound of power-gardening was previously irritating can now delight in the beautiful sound of whirling turbine whine and accompanying roar.
I will also take this opportunity to mention that miniature turbojets are currently made for model aircraft entusiasts, so this is by no means a technologically impossible idea: this only requires one more impeller.
*F.Y.I.: A turboshaft engine is just like an ordinary turbojet, but the power is taken from another impeller in the exhaust which can then be put through a reduction box to give optimum speed/torque for the application. These are often found in 'jet' powered helicopters. See [link].-- TomP, Nov 02 2011 Turboshaft engine http://en.wikipedia.org/wiki/Turboshaft [TomP, Nov 02 2011] Of course. [+]-- FlyingToaster, Nov 02 2011 Have you actually been in the vicinity of one of the model size turbine engines when it's been running? The sound is phenomenally loud, even when compared to a 2 stroke engine of similar output.
Gas turbines also need a good deal of peripheral equipment to start up and run. You can't just crank it up with a pull cord.
However, I like the idea of wheeling out the lawnmower, spooling up the turbine and blowing vast flames into the air a few times before the engine starts properly.-- Twizz, Nov 02 2011 // The sound is phenomenally loud //
WHAT ? WHAT ? SORRY, BEEN MOWING THE LAWN, CAN YOU WRITE IT DOWN PLEASE ?
// need ... equipment to start up //
The coffee-can sized ones have a little electric starter on the front to spool them up, the ground start kit is heavy but quite compact.
// blowing vast flames into the air //
Sadly, this is very rare.
Massive bun for the idea. [+].-- 8th of 7, Nov 02 2011 also, turbine engines tend to be way more expensive than much more easily machined-and-produced piston engines
how about a small OPOC engine (opposed piston opposed cylinder)
I also remember how Stihl a few years back managed to make a four-stroke engine that could work no matter if you hold it upside down or whatever, by getting rid of the oil pan somehow (not the oil though, that still flowed somehow)-- EdwinBakery, Nov 02 2011 random, halfbakery