Silver Case

Spent a good bit of time today diagnosing various faults on my RC trucks.

Spotted a near-miss on the electric hummer.  I had installed aftermarket dampers (shocks) that gave a lot of travel. Except, they were too long, so the drive shaft arms were slowly cutting themselves in half, abrading against the gear box.

Aftermarket Shocks

The Cause

The Near Disaster

These RC cars are great for demonstration the effects of frail construction, feverish vibrations, and high rpms.

Sadly looks like my whole nitro buggy’s differential is ruined. And as far as I can tell from tearing it apart and comparing it to schematics, it’s not my fault. Kyosho (A Japanese Company!) neglected to install an o-ring in the system, so the high-speed rotating shaft was doing its best to commit auto-erotic consumption.

…it breaks almost immediately!

Took it out this morning. Realized the drive shaft that connects the front diff to the right front wheel is bent.  Ran it into a tree branch or something.  It looks like it will still stay in ok.

Take it out to the field and do some higher speed runs. Seems to stall at high rpms, especially on hard turns, so I lean it up.  Now it’s really hummin. It’s horrifyingly fast, in fact. Fortunately I have a huge field behind my house.

Run it for a cycle, and it’s really screaming.  Then notice the engine is shrieking high pitch but it’s losing power.  Uh oh.  The radiator blueing is changing color.  I’ve overheated things. Maybe the melted plastic shrouding is also a clue.  Rich the engine a bit, and send it back out, but it clearly has way, way less power, and sounds really shrill.

Now I have it back at the garage, working on it.  Realize the RF diff/wheel shaft is totally gone. I guess it must have popped out at some point.  Take apart the engine. Hard to see if anything permanently destroyed. See that the glow plug is dead.  I have some replacements.  But I need to do some research before I reassemble and retune the engine.

And I have to go get a driveshaft now, anyway.

7am, in strolls Luke.  He’s ready to drive the remote control car.  And boy, when dad gives a less-than-enthusiastic response to darting out of bed, Dad gets a real (and persistent) earful.

I finally give up when Luke walks into the wardrobe and returns with a par of boxer shorts and a t-shirt, telling me he picked the nice boxer shorts.

But by now, we’ve been hit with a rain shower (low stratocumulus clouds — I think it’s going to rain all day), so he goes apoplectic at the idea we can’t go outside. Coax him to breakfast and wait for a break in the rain.

Now we’re over at the park and he’s driving. I can see he’s getting better and better at making the car do things we wants. He was driving and saying “turn” at the same time he jams the car around.  He also realizes how to back the car out of trouble spots etc.

However, it appears I still have some problems with the transmision, that go beyond the motor mount, so we had to retire the truck.  Today I’ll have to tear it more fully apart and figure out what’s broken.  It sounds clearly that somewhere in the drive train gears are not properly meshing.

So I suggest Luke waits at the park, I’ll run home (100m) and get the Nitro Buggy.

Go to start the buggy. “oh, neat, the pull cord doesn’t retract.”  I can’t coax it to suck back into the spindle.  This is going to be the Nth time I’ve had to take this stupid thing apart (which involves removing the entire rear drive train [8 screws]).

The retractor is dead. Won’t pull. I tried oiling it. Didn’t help.  Then it occurred to me that the spring must have lost its ‘wind’ so I pulled the string out and yanked it so as to rotate the spool and tighten up the spring. That worked.

Get everything back together, fire it up (wasn’t too hard) and head over to the park.

Drive it very briefly and realize the steering control is working poorly/intermittently.  When I walk over to inspect, I see that the fuel tank is spraying a micro-fine vapor of fuel out of the corner of the tank.  The tank is pressurized by some backpressure from the exhuast pipe.  It’s a non-trivial rate of fuel leakage.

By now it’s monsooning again and we head back to the house.

So I’ve removed th fuel tank and see that the two pieces of its construction are pulling away.  I somehow doubt simple glue will fix the matter. Looks more like a melt-the-plastic together solution.  I’ll see to that maintenance job today I guess.

So was thinking I could assemble a 4wd RC car in an evening slightly optimistic?  All signs point to yes.  So far I’ve assembled the rear differential, rear gearbox, rear arms.  Next stop: front diff.

May have to hide this from Luke for another day.