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Page five of the article beginning here.
Before we take it out for a break-in, let's throw in a few items in to insure a good day today. I didn't make too many mods, as I wanted to continue the RTR experience.
Fresh out of the box, the light black springs that come on the Mayhem seemed a bit on the squishy side. From a height of about 1 foot, the buggy bottomed right out when dropped. We've got a couple small but sharp jumps on the small track on our property, so let's bump the shocks up to the light blue heavy springs.*
I usually run 20% in all my nitros, and at the urging of some racing friends I decided to begin with 30% Blue Thunder on this one, mostly because of the larger engine and because it's a new break-in. You should always continue with the fuel you break an engine in on; this RC Car Action article explains why.
A few pre-flight preparations and notes before we put the tires to the clay:
- I'll be using the stock glow plug that came with the Mayhem, but have some spare McCoy MC-59's and MC-8's in the box.
- Gave the entire buggy a go-over with the wrenches, looking for loose screws or anything overlooked in assembly. Normally I'd locktite critical fasteners on assembly, but remember this is an experiment in the RTR experience, so let's see how RTR it is!
- A little preventative measure to lengthen the life of the shocks: a quick wrap of CoFlex as described in this article.
- Do not ever turn over a new engine without gentle lubrication first. Lightweight oils are used in assembly, but depending on how long the model sits on the shelf, this can drain into a worthless drop or two in the bottom of the crankcase. I removed the air filter, loosened the plug, and gave a healthy squirt of after-run oil into the air inlet, gently working the engine over to insure a smooth first start. Another "expert" recommendation here is to disassemble the engine prior to even running it, but I'm going to "RTR" it.
- The stock starter unit comes with a Tamiya connector. Snip-snip, out comes the soldering iron and it now matches the rest of my packs with a Race Prep connector. A 1700 maH 6-cell pack is charged and ready.
- Fresh nimH AA's were used in both the buggy (4) and the TX (8).
- Charge not one but two glow starts.
- Remove the air pre-filter and thoroughly oil the filter, and soak out any excess with paper towel.
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Most important of all is the addition of an Ofna Micro Failsafe. I usually run most of my nitros without failsafes, but considering how cheap these are - I picked this one up at the local hobby shop for $24.95 - this really should never be overlooked. A bad radio signal or interference can cause a runaway and destroy your RC, engine, or both. The failsafe came with a Futaba wire configuration, and it's a simple job to slide out the connectors and slip them into a JR connector in the right order. (Servo Connector Types here.) The setup is a one-step process - squeeze the trigger and press the reset button - and it works beautifully. Turn the radio off and the failsafe promptly shoves the throttle to full brake.
And off to the track we go!
About the Track
2005 has been an interesting season for weather in Oregon. Usually it's hot and dry by May 1st; we've had an unusually wet and rainy season. The up-side is that this has turned my track into a wet, sticky consistency like play-doh. Walking across it sounds and feels like you're walking on a hard sponge. The traction is unbelievable this time of year. The down-side is the drainage ditches on the track have an inch or two of running water in them. Why do you have running water on your track?
Actually "track" is not really a good word for the 100' x 50' area of our property, a "practice oval with jumps" is probably closer to it. Right away, I was a bit concerned our track would be too small for the Mayhem. Unfortunately, the nearest real track is over two hours away. Walk the track with me.
Start it Up Already!
Giddy as a schoolgirl, I filled the tank, tested electronics and checked needle settings, and gave the engine a few cranks to bring the fuel up to the carb. If the angle is a little off, the start attachment will bump the rear diff outdrives and make a hellacious racket. It only took 4 or five short bursts and the Mayhem sprang to life, initially dying after a few seconds. The factory settings (3.5 on the HSN, 2 on the LSN) proved to be just too rich; fuel gushed out of the pipe like a faucet until I dialed it down to about 1.5 and .5! This seemed a little lean compared to most engines I've owned, but it was still running rich, so off we go for the most agonizing part of a new nitro, the break-in.
I'm a firm believer in the under-load, heat cycling method of breakin, and not quite brave enough to try Josh Cyrul's WOT rich method. So for the next three hours or so, it was all I could do to keep it under 1/2 throttle, gently goosing it from idle to 1/4 and 1/2 speed, taking lazy loops around the track, shutting down between tanks, rotating the engine to BDC (bottom dead center, so the piston does not get trapped in the contracting sleeve,) and allowing the engine to fully cool. Running temps were in the low 200's.
During this time I made a few observations. The opinions I've heard about the .26 Sportwerks engine is that it's an entry-level engine and has some problems, but I didn't find this to be true at all. All new engines are tight and feisty until they break in a little, but this one started right up and idled like a champ. It does, however, want to load up more than most engines I've seen. It will idle forever, but if you goose it hard after a long idle it will flood right out and die, even when the needle settings are on the lean side. With constant blips, it will stay running without any problems.
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| Co flex at work, first tank . . . |
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| . . . and fourth. |
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| Temps floated between 220 and 230, but spiked as high as 260 at the glow plug. I'm running BT 30%, and the claim is that the higher nitro content requires a richer setting and the engine should run cooler. Not seeing that today, but will be experimenting with different plugs at a later time. |
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| So is that a buggy or a tractor? This is from the suspension compressing when hitting the jump, even with the hard springs. Didn't seem to slow it down any! |
I would have had better luck with a 2400 or 3600 pack for the hand starter, but in my opinion the starter falls short of expectations for several reasons. While it's got enough torque to turn the engine, it flattened the battery by the third tank. Later when I removed the battery, the Mabuchi 540 had that distinct hot electrical smell, which tells me it was working pretty hard for the short time I ran it. Great idea, will work in a pinch, but falls a bit short.
But it didn't dampen the day at all. The removable starter shaft fit perfectly into my Craftsman 19V variable speed drill. The variable speed allowed me to regulate the cranking RPM's and never faltered for a second. It's coming trackside whenever I run the Mayhem now.
Let 'Er Rip
At the sixth tank, I began leaning out the engine a tick or two, watching the temps, and let it get up to 3/4 throttle. By tank 7 it was time to pull the trigger back.
The power and torque of the .26 engine is awesome, although as I feared my little practice run simply would not allow the Mayhem to shine. I can barely get up to full throttle, much less full speed, and if I'm not tapping the brakes after a half second or so I'm kissing tree trunks or embankments.
There is just so much to be impressed about with this buggy. As I said at the beginning of this article, I'm a newbie to 4WD buggies and have done most of my nitro driving with 2WD offroad trucks. The Mayhem bit down and shot out of corners like a rocket. It was literally impossible to spin out on this track, partly because of the high traction, but mostly because of the weight and design of the buggy. I've heard rumors of understeer and push with this buggy, but these don't show much on this small course. At low speeds I'm getting about a two- to three-foot circle.
Most impressive was the stopping power. While a tap on the brakes brings a smooth landing from the tire-ballooning speed, if you hit the brakes solid the nose dips down, the wheels stop turning completely, and it stops nearly on a dime. AWESOME!
My choice on the springs was probably a good call, even if this sacrificed some handling (none that I could see, it navigated both the fast and slow corners like it was on rails.) Even with the heavy springs, on a high speed approach to the jumps the suspension compressed enough to plow in a little, and the tail dragged a little more than I'm used to on landing. But it certainly didn't seem to slow it down at all, back on the gas and it shot into the next corner with enough authority that I wound up in the water a few times - no flooding or drenching, just a few splashes.
Well. Looks like I'm going to need a bigger track.
Apologies for the poor pics, as my "photographer" had other responsibilities on break-in day. In the second pic below, note the attitude of the chassis - you can see it trying to nose in as it hits this sharp incline.
I went through at least ten tanks on break-in day, and when my arms were about to fall off, I burned up the last tank and pulled it in for the post-run inspection and cleanup. Let's have a look at what I found.
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