Index Home About Blog
From: John De Armond
X-Source: The Hotrod Mailing list
Date: Jun 1992
Subject: Lawnmowers from Hell

>...Aaaah yes, the lawn mower saga continues...


Did you know you can build up the cam with brass brazing rod and regrind
it to your own specs?  Or that the inner valve spring from an old
Honda street bike (who knows what model - junque box farming.)
works just fine for "high rpm" running?  Or that the engine will run
to better than 7000 rpm.  For a few moments :-)  Or that with the blade
and flywheel removed and the ignition running total loss from a
battery, the thing will tach like an Indy car?  Or that nitro will
work until the studs pull out of the head (aluminum block)?

I once built a top fuel self-propelled mower using pretty much all these
techniques.  A motorcycle battery was mounted up front for wheelie control :-)
A quick pass with an acetylene torch opened the front of the deck up so
it became the sythe from hell.  No flywheel, 30 mm motorcycle carb feeding
alky/nitro (20% or thereabouts)  waterpipe header with a HUGE megaphone.
Megaphones were big back then.  The thing would do about 10 mph.  Through
anything.  I used to turn it loose on the wooded field next door.  Just
let 'er wade in.  Stuff flew 30 feet in the air.   The explosion was
even more spectacular.  never did find all the pieces.  :-)


From: John De Armond
X-Source: The Hotrod Mailing list
Date: Jun 1992
Subject: Re: Lawnmowers from Hell

>question for you John, what do you do for entertainment around your
>place, sounds kinda boring to me, hell who wants to watch a lawn mower
>do 7 grand through thick brush while huvering inches off the ground for
>the air flow from the blade thats nearly ready to launch into orbit?
>This doesn't even take into account the gnarly mushroom cloud that
>probably followed the retiremnt of that poor abused B+S motor that tried
>sooooooo hard to hold together!

Well we did later clear that field, build a bunker and declare it
Cape Canaveral North :-)  Even fired some liquid fuel (red funing nitric
acid and kerosene) engines.

You outta seen the Gravely tractor from Hell we built to clear our
first yard.  We bought a HUD repo house whose yard had reverted to woods.
A friend had an old Gravely that did not run which was donated to the effort.
After welding the wheels on to replace the rusted off nuts, the hotrodding
began.  A little port work, homemade manifold, 32 mm Mikuni carb,
header and megaphone and a bit more compression on the old side valve
flathead.  And after the first attempt at starting it, a hopped up
starter motor :-)  Fuel was 20% nitro in methanol.  IN the blade
arena, the front third of the blade housing fell to the acetylene torch.
About 5 lbs of steel was welded to the blade for a bit more inertia.

This lot contained mostly bramble with blackberry thorns and
trees up to about three inches in diameter.  Procedure was to
don a set of duck  canvass ironworker's coveralls and then a
second pair, some GI boots, goggles, a gas mask and ear plugs.
Crank that sucker, set the throttle to bellow, trip the drive
clutch and let the thing wade into the mess.  Dodging the
falling trees was the worst part.  Dodging the thing when it
bounced up in the air was a close second.  When it broke through
the other  side and just before it ate the neighboor's dog, rush
up and pull the  clutch.  I cleared that lot in about 8 hours.
My wife still carries a picture in her wallet of my operating that
thing :-)


From: John De Armond
X-Source: The Hotrod Mailing list
Date: Jun 1992
Subject: Re: Lawnmowers from Hell

>  Now I'm enjoying this thread as much as anyone.  What I want is
>more techie details.  I have a 3.5hp B&S powered Craftsman mower
>that I bought used and on it's way to the boneyard.  I figured
>fooling around with the motor would be a worthwhile screwy project.
>  So what's this about homemade manifolds?  I think I have access
>to an old Keihin carb...

Trivial, my friend.  Just get a hunk of 1/4" thick steel plate, whittle
out a manifold flange that will mount up to the engine (use the old one
as a model), weld on some appropriately sized thin wall conduit and
mount the carb with heater or radiator hose, assuming it is spigot-
mounted.  I whittling tool is generally a combination of acetylene
torch and die grinder with appropriate carbide burrs.

The engine will also greatly (no shit!) benefit from some porting.
Unshrouding the valve stem and under the bowl will pay off.  Be
careful about breaking through to the crankcase.  Since this is a
grenade motor, a bit of MetalSet or equiv epoxee is good enough to
fix any fubar.


From: emory!!scol (Scott Colbath)
X-Source: The Hotrod Mailing list
Date: Feb 1993
Subject: LAWNMOWERS from HELL!!!!

I saw the ultimate L.F.H. the other day on the news. It was a
Smallturbine engined riding mower making about 160 hp according to
the owner. The guy was hanging wheelies in his yard on the newsclip
and he also stated that it would go 60 mph. The funny thing was,
across the front of the mower was an emblem which said "DIXIE MOWER".
Hey John, are you hiding something from us?

[I'll never tell. :-)  I will tell about the "lawn mower" I helped my
French teacher's husband build when I was in high school (helped==welded
some stuff for him).  Running gear was some kind of old car from the
junk yard that had a full chassis.  A large block chevy supplied power.
There was an extra transmission in the drive shaft so the thing could
go reasonably slow and have several gears in reverse.  High float tires
all around.  The cutting head consisted of THREE of those huge triple
blad bushhog heads like the highway departments use mounted in a kinda
triangle with about 10% overlap.  They were all geared together with
motorcycle-type chain and driven from the harmonic balancer.

This sucker cooked!  The blade tips popped like an airplane prop when the
tips go supersonic.  It would mow at about 30 mph.  His goal was to be
able to cut his 100 acre "yard" in two hours.  I think he just about
made it :-)  JGD]

From: John De Armond
X-Source: The Hotrod Mailing list
Date: Apr 1992
Subject: Re: Lawnmowers with >500hp...

>If you really want to tach it up, remove the blade.  It screams then!

yeah but the grass just laughs at the machine.

>Has anyone ever seen lumberjack events?  People actually do hotrod chainsaws
>for competition!

yes. My mentor and teacher of the tuning art used to be heavily involved
with this sport.  His saw was one of the old McCollough gear drives.
The engine was 125 cc after the stroker crank.  Dual pumper carbs and
80% nitro.  An expansion chamber wound around the saw body.  He ran
the thing in a suit and mask similar to the ones used by the old
slingshot drivers.  A sharpening of the blade, using a super secret
angle and edge, lasted one 12 second run through a 6 ft dia log.

>I wonder if you could drive a supercharger (or modified turbo) from the
>blade shaft, or the geared-up wheel drive system...  Don't some
>companies make motorcycle blowers...

I'll bet a Paxton supercharger could be adapted.  Wow!  A supercharged
weed whacker :-)

>Has anyone noticed that the good old days of mowers are gone, now that the
>new mowers say "unleaded fuel only"?

Or worse, what the safety nazis have done to add weight, decrease
performance and reduce cornering performance.  Anyone else a scofflaw
removing this crap?


Index Home About Blog