More marketing baloney

I see that some retailers are selling lawn mowers with their engines
labeled in foot-pounds of torque instead of horsepower. One had an
impressive figure of 6.5 ft-lb. If this thing runs at the max of 3600
RPM it works out to a hair under 4.5 HP. The uninformed buyer won't
know the difference and will get a machine with considerably less
power than he thinks it has.
I wonder if Sears started this. It ain't dishonest, but it's counting
on mass ignorance to sell stuff and I bet it works.
Dan
Reply to
Dan_Thomas_nospam
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The engine doesn't necessarily (or even probably) develop max torque at 3600 RPM. The torque cited may be developed at some speed well above or more likely below 3600 RPM that doesn't happen while mowing.
An engine that delivers 5HP at rated speed (3600 RPM) would be developing 7.3 lbf-ft of torque at that speed.
See
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Briggs 250 cc engine is rated at 7.5 HP, 11.5 lbf-ft of torque, speed not cited for either spec but not to exceed 3600 RPM. 7.5 HP at 3600 RPM is 10.9 lbf-ft of torque so ya don't get the rated torque at 3600 RPM.
Reply to
Don Foreman
7.3 lbf-ft?
Reply to
cavelamb
You're right. That 6.5 ft-lb engine is likely more like 3.5 or 4 hp. Which makes the deception even worse.
Dan
Reply to
Dan_Thomas_nospam
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This Briggs 250 cc engine is rated at 7.5 HP, 11.5 lbf-ft of torque,
Did I get me sums wrong here? Same as 9.89 newton-meters?
lbf is pounds force, the force of one lb of mass accelerated by gravity. Torque is (or was once) expressed in pound-feet rather than foot-pounds to distinguish it from work and energy in ft-pounds. The pounds are units of force in both cases. It used to be that lb was a unit of force and the slug was the English unit of mass but I think that changed and now the pound is regarded as a unit of mass.
Lbf is the convention used by MathCAD. It makes sense to me, and I use it because I rely on MathCAD to keep my units straight for me. YMMV.
Reply to
Don Foreman
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This Briggs 250 cc engine is rated at 7.5 HP, 11.5 lbf-ft of torque,
Ok, I unerstand mo betta now, Don.
I was reading it pound-foot (per?) foot???
But where is the unit of time?
As in pound-foot / second ?
Reply to
cavelamb
It's a push mower. It doesn't take much figuring to realize that push mower engines haven't gotten bigger (other than the fancy plastic housings), burn about the same amount of gas, and still bog down about the same in wet grass with the same size blade. Only the marketing numbers seem to have changed (well, that and the "safety" features). I keep waiting for them to push deck measurements in mm rather than inches.
If they really wanted a proper mower rating, then they would rate them by inches of cut per area mowed per hour, at a certain reference grass density, type, and moisture content. That they don't pretty much says enough.
I saw all of this twenty years ago when I used to work retail, with motor amperage ratings for vacuum cleaners. One mfr. changed over to "cleaning effectiveness amps" and made their competitor hopping mad that their oversized inefficient motor no longer had the biggest marketting number. I had fun telling the competitor's sales rep to stuff it when they cornered me to complain. I happenned to know from talking to our return guy their product didn't work as well--when they worked at all--big motor or no. Now it's all cyclone this, and tornado power that, and completely meaningless, so you have to resort to seeing how much of a handful of sand each will pick up on your own. I was horrible when it came to upselling the units, too, I'd tell people straight up the only thing they got for another $30 on the next bigger model was the $2 headlight.
To tie it all back to metalworking, it's like someone else commented a while back, about a twist drill company losing sight of the fact that in the end, the customer doesn't want to buy a drill bit--he wants a hole.
Give it all the names and numbers you want, but does it cut grass? Does it pick up dirt? Is there a hole the size I need where I want it?
I guess in some ways it's also about customers knowing just enough of the science to be fooled by the marketing, rather than taking the time to really learn the difference. Trusting a marketeer for the accuracy of his science sounds a little like asking the fox to count the chickens for you.
--Glenn Lyford
Reply to
Glenn Lyford

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