(08/10/02) I saw a thread on RMR about a new
Estes' rocket with the capability to determine altitude. I decided to purchase
one from the local Walmart. It is a Ready to Fly rocket (for all practical
purposes) included with a starter set. Launch pad, controller and two motors
(B6-4 and C6-5). The rocket is called the MaxTrax. Walmart sold it for
$18.99. You have to purchase a "button" battery for the nose cone and
the (4) four AA batteries for the launch controller separately.
THE LAUNCH EQUIPMENT:
Not much to say here as it is Estes' standard stuff. The pad
assembles easily by sliding the three legs into the base slots. The rod comes
in two pieces and has to be "bounced" together. The rod, stand-off
and deflector plate then go into the 1/8" slot. It has an adjustable tilt
with a wing nut to loosen or tighten as needed.
The launch controller is a black plastic box with a place
to insert a safety key which lights a bulb indicating continuity. The safety
key has a feature which is nice. It must be pushed in to be active. If you let
your finger off, it springs back breaking continuity. Nice safety add. By
pressing the safety key and then the launch button the rocket is ignited. The
15' wire runs from the launch controller to the launch pad and attached to the
ignitors with two "toothless" alligator clips.
The rocket is Ready-to-Fly after you tie
the pre-assembled parachute to the elastic shock cord. You also need to put the
battery into the nose cone MaxTrax Electronic Capsule. You will need a
small Phillips-head screw drive to do that.
The rocket has fairly nice looks. It has a black plastic
fin can with 4 fins and a motor retention ring. The ring is a twist-lock type
that holds the motor in place during flight. The 1.35" (BT56) body tube is
covered with a holographic looking silver paper with MaxTrax displayed on
the side. The nose cone has a black section and a removable red foam covering.
Not bad over all.
Overall, for CONSTRUCTION I would rate this kit
points . After all, it would be hard to be anything else.
To prepare the MaxTrax for flight, you need to put
wadding in and then place the parachute into the body tube. Next you put the
streamer and nose cone in place. Next place your motor into the mount and twist
on the retainer ring. Slide the rocket onto the launch rod, then your turn on
(or turn off then on to reset from a prior flight) the electronics capsule.
My first flight was on a B6-4 and was straight and
stable. But no reading on the electronics capsule. My second flight was a
repeat and still no reading. Both of these flights were on a perfectly calm day
and in taller grass. So I felt that maybe the electronics capsule needs to hit
a bit harder than the tall grass allowed it.
I tested my theory by setting up the next flight in our
newly mowed lawn. With another great lift-off on another B6-4, the nose cone
ejected and fell to the ground. With great anticipation I picked it up and low
and behold it said 339.1 feet. Success at last.
The next flight was again on a B6-4. It definitely flew
higher and the delay seemed longer (which makes me wonder about the variability
between motors). It ejected and fell to the ground. This time the reading was
411.9 feet. This was interesting because my RockSim predicted 436 feet.
The last flight in this series on a B6-4 gave me another
no reading. Hmmmm. 2 for 5 flights, 40%. That needs to improve.
You may wonder how the MaxTrax electronics capsule works.
There is a small switch that is held in place by the body tube. The capsule is
reset while in this position. Upon ejection the switch activates a timer in the
capsule. When the capsule hits a solid surface it stops the timer and
calculates the altitude based on the time of the fall.
Below is an interesting report from Jeff Vincent that he
said I could use. Check out his experience.
For FLIGHT/RECOVERY, I would rate this kit
½ points . since I have only gained 40% on the readings. The
rocket itself flies and recovers nicely.
Overall, the MaxTrax" Starter Set was a great buy
for $19. It is unique and adds some additional fun to flying model rockets. The
electronics capsule can be used in other Estes kits too. The instructions
mention the Tidal Wave, Ionizer, and Code Red. I'm ready to try it with some C
and D motors! I give the Starter Set an OVERALL rating of
½ points .
For those not familiar with the MaxTrax, it is a new starter kit from Estes
with an onboard "Electronic Altimeter". This uses a capsule which
drops at a fixed descent rate. The capsule physically senses ejection (apogee),
times the interval until it detects landing, then outputs calculated altitude
in feet and meters. Promising...
I had a chance to fly the MaxTrax yesterday (Sat.), which was a
disappointing experience. Tonight, I did some analysis of the data, which was
equaling disappointing. For those not interested in reading further, the short
form is that this is a toy that doesn't work (at least my sample didn't), and,
even if it did work, it wouldn't be very accurate.
First, a couple of bits of foreshadowing. The Estes instructions read:
"NOT INTENDED FOR PRECISE MEASUREMENT". Take them at their word.
Also, the MaxTrax includes a snippet of paper to inform you: "IMPORTANT
NOTICE! "Occasionally, the MaxTrax Electronic Capsule will not display the
altitude after a launch. If this happens, there was an internal electronic
error during the launch or descent. The capsule is NOT DEFECTIVE! Switch the
capsule "OFF" and prepare another launch following the directions.
"If after the second launch, the capsule still does not display the
altitude, there is still an internal electronic error that can be fixed by the
factory. RETURN just the CAPSULE to Estes for resetting or new replacement. DO
NOT RETURN to place of purchase."
As I mentioned in a previous post, I had some trouble getting readings from
my unit in ground testing -- at times under four seconds and around eight
seconds. For that reason, I also hand-timed the descent of the MaxTrax capsule
(ejection to landing) in my test flights, so I could extrapolate the value it
would have returned if it chose to not give an altitude reading.
I made nine flights with a scratchbuilt model (18" BT-56 tube). The
weather conditions were hot but calm at Mt. ASTRE. wRASP gave approximate
altitudes of 220' (for Bs) and 560' (for Cs) for a Cd of 0.6. Here's data from
||not turned on
Several things were noticed from the start. The B flights were not giving
any data, but I wondered if that might be related to the "no data around
eight seconds" glitch previously noted. That's why I went to the C motors
early (I had intended three B6 flights and three C6 flights [and maybe C11
flights] for NARTREK Gold data). Perhaps I should have dropped it into the
nearest mailbox at that point.
Another thing noted was that the capsule had a tendency to tumble on
descent. It has a factory-installed drogue streamer that you are explicitly
told not to alter. However, it seems like it isn't long enough / draggy enough
to stabilize the capsule in a vertical descent. My hunch is that the shock
sensor that detects landing requires a decceleration along the vertical axis --
if it lands at an angle, it may fail to trigger the capsule, resulting in no
Things got more interesting when I moved up to C power. The unit gave
readings (usually), but they were wacky. The highest value given may have been
"close" to (within 33% of) the achieved altitude, but the other three
readings were *way* off (>= 75% error). The capsule was still tumbling on
descent, so I can only hypothesize the the low altitude readings were the
result of it experiencing sufficient decceleration from the tumbling to
prematurely trigger the landing sensor.
On a bright note, my hardware worked fine. The model made nine stable and
successful flights with no damage aside from normal wear and tear (singed but
still quite usable shock cord and mylar streamer).
While the raw data was discouraging, I had some hope that the capsule
descent times that I had recorded would salvage the effort. I could use those
times and the values observed in ground testing to come up with an altitude
figure that the capsule would have reported if it had fallen that length of
time. Tonight, I did that calculation, and the other shoe dropped. Here's the
||Calculated Altitude Reading
Those altitudes are too high (from 13% for the B flights to 36% - 44% for
the C flights). Even worse, the backtracked Cds are way too low (from 72% for
the B to 75% - 83% for the Cs). My estimates may not be perfect, but the Estes
data is just plain wrong.
plan to contact Estes about repair/replacement and any further info they
can give on the unit, but I don't expect it to change my opinion of its
usability. If you are looking for an altimeter you have two choices: spend the
money on a real barometric unit or go the cheap route with a hand-timed
drop-streamer (you'll have to calibrate such a streamer yourself in drop
testing from a known height and calculate altitude from descent times, but your
efforts will yield a cheap, reliable, replaceable method of altitude
by Jeff Vincent - Rocket Cynic
(Contributed - by Mark Fisher - 09/10/02)
A new member showed up at our launch one weekend with a MaxTrax (EST1434), a
new starter set from Estes that included an altimeter payload. He had flown it
once before and it had claimed an altitude of over 700 feet on a C6-5. When he
flew it at our launch, he used the other included motor, a B6-4, and it
registered over 350 feet. The shock cord separated, but after some repairs
carried out by some of our other members, the bird flew again that day.
At the time, few on-line vendors even listed the MaxTrax, and those that
did had it marked as "overdue" or "not released". The flyer
in question found his at a local Meijer, and as I had to go get cat food that
evening ("uh ... yea, cat food, that's the ticket"), I stopped by the
new rocket display at my local store, and there one was. The price was a
stunning $21.99 (list is $39.99 and the cheapest I saw it on-line was ~$28), so
I snapped it up.
Recovery systems, as noted below.
The altimeter is housed in a black styrene capsule that fits into the body
tube. On the other end is a foam rubber nose cone tip that fits over the molded
"thumb" of the altimeter bay. Despite claims to the contrary, two 1.5
V calculator button cells for the device are included. A nice touch. Mine were
Vinnic model L1154, though the more common silver oxide models 357 and A76
would last longer. Only one is required so the other is a spare. A very nice
touch. To install the battery, the capsule's rubber tip and two tiny, deeply
recessed Phillips head screws must be removed and the halves folded open.
The battery fits in
a molded holder in the "thumb" with a flip-away upper clip, and the
altimeter is in the body.
The electronics are a custom PC board with a single chip covered in carrier
material. The board also mounts the on-off switch, LCD display and shock
sensor. Off-board is the ejection-detect switch that is held open by the body
tube, and closes when the motor charge separates the capsule from the rocket.
With only three moving parts and minimal wiring, the device promised to be
relatively durable. I was a bit worried that ejection gasses might enter the
bay though the two switch openings, but I've yet to see any evidence of that.
As I had designs on this little gizmo for some other birds, I wanted the
thing back, so I modified the MaxTrax carrier rocket extensively before its
first flight. I added a length of 300# Kevlar
and upgraded the elastic to 1/4 inch from the included 1/8th inch wide junk. I
also replaced the included pre-built 12-inch plastic chute with the same size
Rogue nylon unit, and added an HSPP-4Y Medium HeatShield from Pratt Hobbies.
The altimeter capsule is supposed to recover by streamer, but as our launch
site is surrounded by tall grass, I added a large snap-swivel to the elastic
and hooked it to that. Total dry weight after the modifications was three
ounces even, and with an estimated drag coefficient of 0.573, I predicted the
altitudes found in the estimated performance table below.
As Estes only requires you to assemble the pad, insert the included battery
and attach the parachute to the shock cord, the assembly of the bird in stock
configuration is pretty easy. As it is likely to fail after just a few flights,
though, I'd only rate this bird a 2 on the Essence scale for assembly, needs
The bird is a standard Estes BT-56-based RTF, with quick-change motor mount and
the new two-lug one-piece launch guide. The shock cord is attached though a
hole in the body tube to this, making for one of Estes' worst mounts ever, and
that's saying something. The body wrap is a nice silver holographic sticker, so
the bird will be easy to see in the air, and overall, the rocket is a rather
good-looking example of the RTF genre. The launch system is Estes' standard
Electron Beam, in all black.
out of 5
I flew the bird nine times in my configuration, on five B6-4s and four C6-5s. I
didn't get an altitude reading once. I called Estes and they said that the
reason the thing wasn't working was because I had it tied to the parachute. I
reconfigured my MaxTrax back to the way Estes intended it to be, swapping out
the 12 inch parachute for a 9 inch version. I flew her on the recommended
motors again, with the following results.
||Not armed, hit road
Fearing that the unit I had was defective, I broke out my back-up MaxTrax
and flew it for the last three flights. The ejection sense switch on this unit
was intermittent, and it took a little adjusting to get it to work
consistently. The two readings I got from it were just as bad as the ones from
the first unit, and this capsule was lost in only moderately tall grass on the
third flight. Two of us saw right where it came down, but we gave up after
thirty minutes of searching. The bird itself survived its repeated flights
This is how I think MaxTrax works. The ejection sense switch starts an
internal timer, which is stopped by the shock switch when the unit hits the
ground. The assumed descent rate is then multiplied by the elapsed time to
determine the altitude. If the shock switch is activated prior to touchdown
(the capsule does tumble pretty badly, the streamers did not keep either of my
units pointed straight down), the altitude will be low. If the shock switch
isn't activated at touchdown (as it will not be when tied to a parachute), no
altitude will be displayed. If the capsule does not fall at the assumed descent
rate, the altitude will be erroneous. While the idea behind the MaxTrax is
ingenious, it just doesn't work in practice, at least not the way Estes has
The bird is over stable and does have a tendency to weathercock. At 2.5 ounces
in stock trim, the B6-4 is late, but the C6-5 is nearly perfect. These are the
only two Estes motors you can fly in the stock bird, though, limiting the
altimeter to two general altitudes, somewhat boring. If it worked, that is; the
values I got from my two units just aren't believable. I'd rate the flight
characteristics of the MaxTrax a one on the Essence scale, needs a lot of
out of 5
When I initially saw MaxTrax, I imagined all the kids that would be using it
for their school science projects. Once I got some experience with the thing, I
realized that there were going to be a whole lot tearful young scientists and
frustrated Dads this year. Twenty-one flights on an RTF has got to be some kind
of record, but I'm afraid that my MaxTrax's durability was due to my preemptive
mods. Given the overall quality of the bird, poor altimeter design, limited
flight scope and ensuing high possibility of disappointment, I'd rate the
MaxTrax a 1½ overall on the Essence scale, needs drastic improvement.
½ out of 5