Member postings for Maurice Taylor

It shouldn't be too difficult to work that one out!

My hover style mower is getting long in the tooth and recently watched a QVC advert for the new GTech (platinum) mower, as we have GTech products (hoover etc) I decided to go for it as it was a good price.

I have lawns front and back and have cut through the cable a few times on my old mower, Using the new GTech mower I managed both lawn areas with the battery showing half left, grass collection is good, did a reasonable job on the lawns.

Much easier to use and does have a carry handle, though definitely not lightweight.

My wife likes the GTech products and recently bought the new GTech Platinum hoover, which she thinks is much better than the old one.

Like anything else in this world, you get what you pay for generaly.

Of course, those with petrol mowers are like those on here with MYFORDS...............

oneupmanship is everything

Two-stroke have a higher power-to-weight ratio than 4-stroke, but 4-stroke are more fuel efficient and the exhaust is cleaner. Being more complicated 4-stroke are more expensive to make. So you tend to get 2-stroke engines when a cheap dirty noisy inefficient light-weight power unit is beneficial: usually open-air stuff like lawn-mowers, chainsaws, ATVs etc. 4-stroke engines win as soon as fuel economy, quiet, or cleanliness matter. Motorbikes are interesting because they straddle the line: sometimes 2-stroke, sometimes 4.

Whilst it's possible to build a reversible reciprocating IC engine, it's rarely done. 2-strokes don't require much modification, basically move the timing and spin it backwards. It's a cheap way of providing vehicles that rarely reverse with the ability. Might ask if it does the engine any harm, and the answer is yes, after a while, but not so it matters for occasional reversing. Did 2-stroke Bubble Cars have reverse? I seem to remember people had to get out and push!

Reversible 4-stroke engines need a complete second set of valve control gear, making them extra complicated. Sometimes done in ships to avoid installing a monster gearbox, but generally avoided. The lengths shipbuilders go to avoid fitting gearboxes is another story!

Dave

Dunno about the Aquarius engine, but Toyota claim 42% for their free-piston engine, which is rather better than the average reciprocating engine, which are usually less than 30% efficient, even when not idling at traffic lights.

Choosing a motor isn't simply about efficiency though because different motor types suit different operating conditions:

• Turbines are highly efficient,- well over 30%, and reliable but only at constant high rpm, no reverse. They easily outperform reciprocating IC in long-haul aircraft and for generating electricity, but are terrible for variable speed applications like road vehicles.
• Reciprocating IC engines are complicated (more maintenance), don't reverse, and are relatively inefficient, but they have a high power to weight ratio, convenient fuel, and can vary RPM over a reasonable range. Supported by a gearbox, they do well in road vehicles.
• Steam reciprocating engines have high start torque, but low efficiency (<5%), and massive boilers. Main advantage, they aren't fussy about fuel quality. Otherwise, almost entirely obsolete.
• Electric motors are efficient (>60%), high torque over a wide range of RPM, reversible, simple and reliable. Their Achilles heel is the need for a power supply, but whenever mains power is available, they slaughter other types of motor.

Free piston engines look to be a good option for Hybrid EVs. They're compact and don't need a big engine compartment. And their high efficiency is well suited to generating electricity. May only be a niche application, but the type could be important in future.

Dave

You need a licence to own, sell, make, repair or service a fruit machine. They don't make a distinction on size.
You can get a relatively cheap single machine permit for personal use. In theory even friends are not allowed to put money in a personal machine. And you can't fix a friends machine either.
https://www.gamblingcommission.gov.uk/licensees-and-businesses/page/single-machine-permits

Robert G8RPI.