[AT] Horsepower Question

[carl gogol]

Dave-
I don't know, I have never tried it.  Meltdown is perhaps a term I used with 
a bit too much visual impact.  It would probably just have bearing seizure 
and distortion, maybe with a synthetic oil the engine would eventually run 
hot enough to approach meltdown.
They are rated as "Peak HP" for a reason, you can't expect them to produce 
it continuously!  If you do, the waste heat and commensurate temperature 
rise due to their inability to shed enough heat is the issue.  If it wasn't, 
the manufacturers would rate them even higher.  Even tractor engines can be 
driven hard enough to overheat, but we usually see the radiator blow off and 
it stops us.  You don't get that clue with an air-cooled engine.

Carl Gogol - Manlius, NY
Tasty grazing in the Oran valley of Central NY
AC D14, 914H
JD 5320 MFWD
Kubota F-2400, B7300HST

----- Original Message ----- 
From: "David Rotigel" <rotigel at me.com>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Sent: Monday, October 11, 2010 10:11 PM
Subject: Re: [AT] Horsepower Question


> Thanks for the info Carl! Has this sort of "meltdown" ever been tested?
> Dave
>
> On Oct 7, 2010, at 7:38 PM, carl gogol wrote:
>
>> Dave-
>> I only check personal email once a day so I am a bit slow in
>> answering.
>> In order to control end cost, the cooling of these small lawnmower
>> engines
>> are not designed for cooling more than the average anticipated
>> load.  The 20
>> HP rating is for peak horsepower, which it might be able to produce
>> for a
>> few minutes without the engine getting too hot.  However, if you run
>> it
>> continuous at the peak HP its temperature will quite rapidly rise
>> past the
>> design temperature limit.  At that point it is just getting worse
>> faster as
>> the temperature goes up the oil breaks down and the friction
>> increases and
>> ....
>> To produce peak HP you are requiring a higher throttle setting than
>> the
>> continuous load rating in order to get more fuel into the cylinder
>> -- which
>> produces proportionally more waste heat.  These engines might be
>> able to
>> continuously provide 10 HP (maybe less) because usually no more than
>> that is
>> needed.  There is enough mass in the block to absorb additional heat
>> for a
>> short period, but then the block's temperature starts to rise fast
>> due to
>> its limited cooling area.  No problem for a short period, but
>> continuous
>> full production at maximum short term rating will cause failure due to
>> temperature induced bearing and piston failure.  They are aluminum
>> after
>> all.  If you want to try this, do it on a real cool day because on a
>> hot day
>> it will be over quickly.
>> Carl Gogol - Manlius, NY
>> Tasty grazing in the Oran valley of Central NY
>> AC D14, 914H
>> JD 5320 MFWD
>> Kubota F-2400, B7300HST
>>
>> ----- Original Message -----
>> From: "David Rotigel" <rotigel at me.com>
>> To: "Antique tractor email discussion group" 
>> <at at lists.antique-tractor.com
>> >
>> Sent: Wednesday, October 06, 2010 8:09 PM
>> Subject: Re: [AT] Horsepower Question
>>
>>
>>> Hi Carl, Why would that be the case?
>>> Dave
>>>
>>> On Oct 6, 2010, at 7:26 PM, carl gogol wrote:
>>>
>>>> If your lawnmower engine had to actually produce 20 HP for an hour
>>>> it would
>>>> probably melt
>>>> Carl
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