One thin mint...

The last three evenings have been "testing" mode.  Yes, it is basically done.  Always room for improvement, though.

Day 1:

First trip out, no blade.  Drove it around the yard to get the feel of it and see if it would dig up the grass with the tank steering.  Good news, handles well, good speed, doesn't dig the grass up unless you make a really tight turn or a "sit and spin".  Back to the garage for the blade.  Oops, wait, one of the wheels is coming off, make that three.  The bolts weren't tight enough.  Found the bolts with magnet bar, put them back with double nuts (jam nuts).

Installed blade, stand back - way back, start - no flying death!!!   Cool.

Down to the hill which is sorely in need of mowing:

Observations

• Grass is tall, mower doesn't bog, clog, or toss huge clumps.  Not bad for never having designed a mower deck before.
• The pic above shows the engine on the downhill side.  There is only about 1/4 tank of gas and mowing uphill starved the carb of fuel.  Gravity feed doesn't work too well, may have to add a raised aux tank.
• The two large group 24 marine batteries are HEAVY, about 44 lbs each.  The design put them in the back over the two axles being careful not to create an overhang.  In CAD, everything was flat and level.  Running uphill at about 45 degrees, a sizable fraction of the rear battery is behind the rear axle and the CG is probably above the axles to start with.  On the slope, goosing the throttle or stopping quickly going downhill causes the front to rise slightly - or generally more than I'm comfortable with.
• Alternator belt needs tightening, old school, no spring tensioner.

Back to the garage.  On the way, can't resist doing a spin move in the gravel part of the drive - wheeee!  Crap, another wheel is coming off.  Wait, the nuts didn't come loose, the bolt sheared off!  Purposely used ungraded fasteners to preserve axles in case of high stress, but apparently a rough turn is enough to trip these shear pins.

A link to maiden voyage ( ignore belt squeals please ) - YouTube Video

Day 2:

Replaced all wheel bolts with Grade 5 hardware.

Tightened up the belt a little more.

Added 40 lbs of ballast to front of mower ( eight 5 lb barbell weights left over from son's high school football weightlifting years )  Tie wrapped on temporarily to test.

Back to the hill, loosing daylight, but had to try it out.

No broken parts, balance is much better, no more belt noise, adjourn to the garage and call it a success for the day.

A little research in the late evening on alternate solutions to weight distribution and ballast mounting options.

Day 3:

The evening prior, I was looking into smaller batteries.  The two marine batteries were originally intended to power the machine without an alternator for about an hour.  Since I had already bought them and didn't think the weight was an issue I used them.  However, since I chose to do the alternator anyway, I didn't really need that deep of a reserve.  I need to run the mower on electric only out of the garage, down the drive and down the hill before I start it - maybe a 800 ft or so.  Likewise I need to make the return trip, especially if I run out of gas.  Even so, I should be able to do that if I consider the mowing time is essentially free, Amp Hour wise.

I thought about ordering some gelled electrolyte cells, but they generally require low current charging and aren't well suited to alternators.

Then it hit me, lawn tractor battery.  They are just mini car batteries essentially, and are widely available.  Most auto stores carry them, but mostly in a 280 CCA size.  Turns out Tractor Supply has 420 CCA ( U1 size ) batteries for about $50 each.  Two of them are smaller than one of my group 24s, and shorter, and less than half the weight.

Picked up two on the way home, and mounted them up.  I used a piece of wood to space them forward and keep them there.

Removed the front ballast and here we are:

Return to the test hill and finish mowing before the rain?  Sky looks a little dark.

Observations

• Mower is peppier with the reduced weight.
• The front end is still a little light, so will probably add maybe 10 lbs  to the front to help reduce scary behavior.  It is *way* better than before, able to tackle even steeper sections than previous day with only mild moments of panic.
• May also help to increase air pressure in the tires to reduce bouncing and squatting under weight shifts.
• Filling the gas tank all the way full allows full inclined mowing in the proper forward direction ( favorable to avoid oil loading the backside of the piston if oriented downhill )
• I really need to program my radio transmitter to correct for the proper stick direction for forward/backward and left/right.  Both drive channels are backwards making steering interesting.
• No issues making it back up hill on electric only with smaller batteries.  Voltage starting was 25.6 V and 25.4 after I returned and let it sit for a bit.  Overall it is not severely depleting the charge.
• Motors were not hot, nor were any of the cables.  The fan on the motor controller has not yet tripped on, shows the controller is comfortable with the current demands.
• It's kind of nice standing 10 or more feet away from a mower.  My clothes stay clean and I'm not getting grass pollen and dust all over me.  My allergies will thank me.