Futaba 3UCP 3D printed battery cover

Last year I purchased a couple of Futaba 3UCP transmitters on eBay that were missing their battery covers.  Here are pictures of one of them, front and back.

Futaba 3UCP 3 channel 2 stick transmitter (front)

Futaba 3UCP 3 channel 2 stick transmitter (back)

Futaba 3UCP battery compartment

Both transmitters were in good condition with only minor blemishes from usage.  The single major problem with each of them was the missing battery cover.  Apparently, the original owner was using some sort of larger battery pack and misplaced the covers over the years of owning them.  The seller, who seemed to be a clearance house company, searched for them to no avail when asked about them.  Knowing the covers are practically impossible to find, and with no response from Futaba support, I bought the radios anyway at a reduced price due to the missing covers.  The hope was that I'd find some hole-in-the-wall place online or eBay auction with covers for sale at some point.  I knew this would be unlikely, but worst case, these units could be useful as spare parts for my somewhat large collection of 3UCP transmitters if anything ever went wrong with them.

Here is what the original battery cover looks like:

Original Futaba 3UCP battery cover (front)

Original Futaba 3UCP battery cover (back)

After studying the OEM cover in detail, I decided it might be worth trying to see if I could create a 3D model of the battery cover and have it printed in plastic by a company like Shapeways (http://www.shapeways.com).  Having practically no experience in 3D modeling and design, I asked people on the TamiyaClub forum what they use for design software.  One person suggested using Rhino, but the trial version lasts 90 days and the full version was US $1000.  Although I figured I could create the battery cover in under 90 days, I would ultimately be left with nothing to use after that point in case I wanted to create other things for printing and I really didn't want to spend any money if at all possible.  In the end, I used Blender (http://www.blender.org) because it was free and appeared to have a fairly large user base, including many helpful tutorials on Youtube. Blender also seemed to be fairly powerful with many features that could allow my 3D models to become more complex as my skills improved.

After 10 hours of measuring the original battery cover, reading and watching tutorials and playing around on my own, I finally had the first version of the cover ready.

I created an account on Shapeways, uploaded the model and ordered it in strong and flexible plastic dyed black.  After a week and a half, it was delivered to my door.

Incredibly, it fit into place and actually snapped shut with a very nice clicking sound much like the original part!  I had to file down the top two corners because I forgot to round them in the 3D model, but I was amazed that my very first try at 3D printing actually worked and was completely useable.  The printed cover certainly wasn't perfect - it had gaps around the edges and did not contour perfectly with the transmitter back cover, but with some tweaking I was sure I could make it look and function even better.  

For version 2, I added some rounding to the two corners that I had missed and widened it so the door wouldn't show such large gaps on the sides and top.  I also pulled the bottom rear curved part back a little bit to make it larger than a 90 degree angle in order to more closely mimic the original door contour.  I had missed these things during my initial measurements and modelling.  I uploaded version 2 to Shapeways, ordered it, and waited another couple of weeks.  Here is version 2:

The second version functioned better and looked much nicer than version 1 when installed. The width was now perfect and the overall fit was much tighter, but I still wanted to make a couple more minor tweaks to the door in order to get it to fit more closely like the original part.  I increased the size of the rear stubs so the rear part of the door wouldn't lift as much and show a gap, added material to the hook part of the front barb so the door wouldn't pull down as much and leave a gap and finally enlarged the "OPEN" text so the 3D printer could have an easier time with it.  Upload, order, wait.  Here is version 3:

The third version fit very well with the same pleasing "click", but the looks were not quite as "clean" as the second version.  By clean, I mean it didn't quite fit snug at the top and sides like version 2, which had practically no gaps.  I do not know why this happened, because I did not modify those dimensions in version 3.  Also, it looks like a different model or brand of 3D printer created version 3 because the plastic looks and feels slightly different.  This may explain why the fit isn't the same as version 2.

At this point I thought I was playing within the realm of the resolution of the 3D printers themselves, so further attempts at refining the door might result in something that no longer functionally fit depending on which 3D printer created the part.  I decided that version 3 would become the final product.  3D printing is very different from a mold where each part comes out exactly the same.  Some variation is to be expected each time an object is printed, though it is usually very minor.

I created a store on Shapeways and enabled the ability for others to purchase it for themselves.  If you have a Futaba 3UCP transmitter that is missing its battery cover, you can now order a 3D printed one on Shapeways by clicking here.  Please note that the 3UCP battery cover is unique to this model and does not fit any other Futaba transmitter.

Time for a new battery charger

For many years I have used Tekin BC112c AC/DC chargers to charge my NiCd and NiMH battery packs.

I own four of these chargers.  They have all been upgraded to the latest firmware (H31) by Tekin in order to support charging NiMH batteries in addition to NiCds.  Since I deal with mostly vintage cars, I still have not moved to LiPo or even brushless motors.

As for the BC112c, I really like the features and functionality it provides.  Variable charge currents are selectable in 10mA increments between 0.1 and 10A and from 1 to 12 (NiCd/NiMH) cells.  Trickle charge current is is also programmable.  Multiple charge modes including re-peak for just before a run and timed charge mode are available.  Last year, however, I had two chargers out of four fail on me for unknown reasons.  They were working perfectly and then suddenly they freaked out with power issues. 

With the two failures and doubts about the remaining two chargers, I decided it was time to buy a new charger (or two).  I knew I wanted a charger that could be powered via AC rather than just DC.  Yes, I know; if I bought a DC-only charger and an AC to DC power supply, I could keep using the AC power supply going forward no matter what charger I decided to buy in the future.  But I did not want to have to lug around two pieces of equipment and I wanted to buy enough chargers to allow up to four batteries to be charged simultaneously.  One AC power supply might not be enough juice to power multiple chargers at once.  Maybe someday in the future I will break down (again) and buy an AC power supply and DC chargers, but this time I wanted a charger that was AC powered.

My requirements were:

• AC powered
• Suport for 2 or more batteries fast charged simultaneously
• NiCd, NiMH and LiPo support

It's a pretty short list.  I purposely kept it short and simple because otherwise I'd have to look at chargers that were either DC-only or extremely expensive.

There are tons of chargers out there today.  The selection is quite broad, but with my short list of requirements I narrowed it down to just a few different makes and models.  It really boiled down to which chargers were considered good quality and had favorable reviews by people that actually used them (instead of just relying on the press reviews). 

In the end, I purchased two Duratrax Onyx 245 chargers.  I mostly decided on the Onyx 245 based on the fact that it won reader's choice awards in RC Car Action magazine multiple times.  I figured the people that use them every day would know what charger is good.

The Onyx 245 charger comes with Tamiya, Deans and Traxxas charge leads which is a nice plus.  Since I use Deans plugs in all my cars, I did not need to purchase any extra connectors.

After using the Onyx 245 for a while now, I have to say it is simple to use and appears to charge well, but it really is one of the most basic chargers out there.  By basic, I mean that there isn't one feature they could remove from its functionality and get away with it.  It has the absolute bare minimum of features and functionality in order to perform its function and nothing more.

Some of my complaints and wish-list items (not in any particular order) are listed below.  Many of these things I knew about before I purchased the charger, but I still think they are valid:

• Trickle charge is not available until after fast charging has completed.  A battery cannot be trickle charged just by plugging it in.  I wish trickle charge was available for NiCd and NiMH types independent of fast charge having been used or not.
• Charge currents are limited to 0.5A, 1.5A, 3.0A and 5.0A.  Nothing else.  I wish the fast charge currents could be configurable in 0.1A increments.
• Trickle currents are hard-programmed based on the fast charge current and cannot be changed.  I wish the trickle charge currents could be configurable in 0.01A increments.
• Settings are not saved so every time the charger is plugged in you must select the battery type and fast charge current (unless you like to use the default LiPo and 5A settings).  I wish the charger saved the last selected battery type and charge current for next power-up.
• Beeping and alarms are always on and cannot be turned off, nor is there a volume control.  I wish there was a way to turn down the volume and choose a different beep tone/style including a setting of 'off'.
• DC input plugs (alligators) are hard-wired.  I wish they were banana plugs like the battery outputs so they could be unplugged to reduce clutter.  The dangling wires and clips are always getting in the way.
• The AC cord is too short.  I wish the cord was two feet longer.
• The LCD display does not hold still while charging.  What I mean is that during a fast charge the display is constantly switching between battery voltage and charge current every 4 seconds or so.  Pressing the Data button repeatedly will allow you to cycle through battery voltage, charge current, total mAH charged to battery so far and charge timer.  But after a couple of seconds, it switches from whatever it was displaying back to battery voltage and charge current again.  This is annoying.  I wish the LCD display would stay on whatever screen was selected via the Data button.
• This problem is by far my biggest complaint:  Plugging in a battery while the other side is fast-charging a pack will often cause the whole unit to reset.  The small spark of current that sometimes occurs when plugging in a discharged battery (NiCD or NiMH) can cause the whole charger to reboot.  There is insufficient power supply and/or surge current separation between the two "independent" charging circuits and the main power supply.  The reboot is extremely annoying if there is a battery being fast-charged on the other side of the charger at the time.  Some type of electrical noise/surge suppression should have been designed into the charging circuits or shared power supply to prevent this behavior.  It happens often enough (50% of the time) that I refrain from plugging a second battery into the charger if one side is fast-charging.  I wait until the fast-charge cycle is complete before plugging in the second battery.  I've never seen this happen if neither side is fast-charging.  Both of my chargers do this, so it isn't a "one-off" problem with one unit; it's a design problem.

One other minor manufacturing/design nit:

• Quality Assurance failed to notice that on one of my units the fan was rattling quite noisily during fast charging.  After opening the charger up I discovered the molded fan mounts were simply too loose and allowed the fan to vibrate in the mount.  Two tiny slips of paper solved that issue by holding the fan securely in the slots.  Easy fix, but shows that it is a cheap design.

Of course many of the items I complain about above are available on higher-end chargers and even the new soon-to-be-released Onyx 225 has many of these features, although it can only charge one battery at a time.  Maybe that's a good thing, though, considering the problems I have when plugging in batteries into these Onyx 245 units when they are already fast-charging another pack.

As for charging performance, the Onyx 245 does a good job of charging NiCd and NiMH battery packs, even old ones like I have.  As for LiPo, I cannot say because I do not own any LiPo batteries that could utilize this charger yet.

Would I recommend the Onyx 245?  I suppose I would, but only if you are looking for a basic charger with no bells and whistles and you want to charge two packs at once and can deal with its limitations.  Frankly, I expected a little more from a US $120 charger.  It's a workhorse charger and works fine for what it does which I suppose is why it keeps winning the reader's choice awards. I'd say go for a higher-end charger like the soon-to-be released Onyx 225 if you are looking for more features and finesse, however.  I may end up doing just that.

Tamiya Madcap Number Three

This is the third Madcap I've rebuilt so far and it is also the second one of the batch of three I got earlier this year when I was on a Madcap shopping spree.  I call it Madcap #3.

Here is the car as I received it.  It came with an AM radio that was apparently modified to get power from an external battery pack (see wires).

Yeah, I know.  The wing decal is on backwards.  I didn't build it!

Damage was pretty standard issue as Madcaps go:  Rear chassis breakage/splitting around the gearbox mount (can't see it in the photos), a broken C3 rear gearbox mounting post (first time I'd seen that), but surprisingly no broken front chassis posts.  The motor was a stock Mabuchi RS540 with a broken wire tab that couldn't be repaired and it stunk like a piece of machinery that had been extremely hot at some point with that "hot oil" smell.  No visible damage, just smell.

I decided to install the optional metal motor plate in order to reduce flex caused by a (hopefully) more powerful motor and perhaps absorb a little bit of heat as well.  Ball bearings were used throughout, but I kept the stock gear set with a Robinson Racing 23T 0.6mod pinion and the standard 70T spur.  I figured I'd test whatever motor I chose with the standard ratio first and go from there.

I didn't take any pictures of the build, but it wasn't very eventful anyway since it was basically a standard stock build following the manual.  I used black CVA shocks again (50519 and 50520) like Madcap #2 since the performance is improved so much versus the stock friction shocks. 

The only interesting part of the build was the use of Avante aluminum posts as a drop-in replacement for the broken C3 gearbox mounting post.  I'd heard they could be used on the forums, so I bought a bag of parts from eBay to test the theory.  Each bag comes with three posts and a bunch of other junk, so two bags will refit three cars.  It turns out that the parts are exactly the same dimensions as C3.  Just the standard self tapping screws have to be swapped out for 3mm machine threaded ones and that's it.

Now for the motor choice. I wanted something with a bit more power and speed.  I have a small selection of motors that I purchased from others over the years, almost all well used.  Many of these motors are standard 27T stock variants which means the performance is fairly known and predictable within a certain range, which is to say rather boring.  But a few of the motors have an unknown number of turns on the armature, so it is fun to try them out to see what they are capable of.  The Demon Power motor that I used in Madcap #2 was one of the "unknown winds" that unfortunately turned out to be rather disappointing once I ran it, so this time I was determined to find a motor that had more power.  After looking at the various choices in my collection, I decided to use a Fantom motor with seemingly no other identifiable markings.  I did not even power it up to test before installation to see how fast it spun.  I mean, all of the used motors in my collection have been disassembled (if it is possible), cleaned and oiled before being put away, so I knew the Fantom was in good working condition, but I did not remember how fast it was when powered by the 4 AA pack that I use for motor testing.  Basically I was blind to what the motor was capable of.  It could be another slowpoke like the Demon Power or it could be a real powerhouse.  I figured it would be fun to find out and compare.  I forgot to take a picture of the motor by itself, so here it is fully installed with the label partially hidden by a heatsink.

Here are some more pictures of the finished chassis and original body.  The body actually cleaned up a little and got a bit whiter which was nice.  There is paint missing from a bunch of spots, but it is still usable.  The wheels and tires are from Carson Motor Sport in the UK.  The chrome rims are bright, but I think they go with the body color well enough.

I used a Futaba S28 servo for steering along with a G to J conversion cable to connect it to a Futaba R113ip receiver.  The speed control is a Futaba MC330CR.

Performance
With the stock 23T / 70T gearing and the Fantom motor, this car was a rocket ship!  Massive power and incredible speed.  In fact, it was almost too much speed.   It was hard to hit full throttle without running out of pavement.  Not only that, but just letting the car coast felt like the brakes were on because the motor magnets were so powerful.  After a few minutes of driving, I touched my finger to the motor can to feel how hot it was and I could tell that I needed to gear it down or I'd damage the motor.  I swapped the 70T spur gear for the 77T and also switched out the 23T pinion for a 21T pinion (the largest that could fit given the motor mounting screw slot size on the metal motor mounting plate).  This changed the pinion/spur ratio from 1:3.04 to 1:3.67.   The new ratio definitely reduced the heat output of the motor, but I felt that it needed one less tooth on the pinion, so I replaced the 21T with a 20T.  This changed the gear ratio to 1:3.85 and resulted in great motor temperatures while still providing incredible speed and amazing power.  I added a black vertical finned heatsink to help dissipate heat and I believe it does help a little.  Getting the heat to transfer through the motor label via a clip-on heatsink is not ideal, but I think it's worth it.  

Launching the car from a standstill or a slow forward roll results in the back end sinking down to help get more traction thanks to the black oil filled CVA shocks and their smooth movement.   Conversely, hitting the brakes actually lifts the rear end and drops the front down a bit.  The power provided by the Fantom motor is quite amazing considering it is a well-used example that might be over 15 years old and it's being powered by NiCd batteries that are probably close to 10 years old.  If I had to guess, I'd say the Fantom is a 9T or something simply because it is so fast and powerful. 

Given all of that power, I know what you're thinking.  The poor Madcap ball diff cannot possibly stand up to such a powerful motor without disintegrating.  Maybe this is true, maybe it isn't.  All I can say is that the diff has not even given me a whimper through over 8 battery packs of running.  No squealing, no loss of power, just great power delivery and the awesome whine of the Madcap gearbox.  I also purposely do not thrash on any of my cars and try to deliver smooth power commands.  Also, since I'm not really doing much off-roading or jumps, drivetrain shock is minimal.  I did use the optional shims when building the diff because they certainly do help.  I know because when I first built the diff without the shims and tested the car, it squealed a bit under high acceleration.  I added the shims and it's been great ever since.  I should mention that I used Tamiya ball diff grease, not just any old grease when rebuilding the diff.  Ball diff grease is specially designed to not let the balls slip whereas other greases would allow slippage.  This is a key thing to remember.  Also, I made sure all diff parts were thoroughly clean before rebuilding it.  All parts went into a motor cleaner bath until everything was clean and then the rebuild was started.  All it takes is a single grain of grit or sand and the diff can be ruined.

Of the three Madcaps I've rebuilt so far, this is my favorite one to run.  But I still have one more Madcap rebuild left, so stay tuned!

Love the Tamiya Madcap

I really do.  It's a great car.  I missed it when it was originally released in 1989 because I was just starting college and had no money for RC.  It isn't a particularly spectacular car and certainly has some weaknesses, but it's fun to drive and work on.  

My first introduction to the Tamiya Madcap chassis was actually a Saint Dragon that I bought on eBay.  The chassis was too nice to use as a runner since it was never really completely finished by the original owner, so I decided to purchase a Madcap to use as a runner.  Even though the chassis was well-used, it was in good enough condition to warrant purchasing a reproduction body and original decals.

After restoring the first Madcap, I wanted more.  I wanted to try the chassis with different motors to see how it behaved.  I wanted to try some Thorp hop-ups such as the 48P gear conversion kit including the Thorp ball differential.

At the beginning of this year I bought three well-used Madcaps to go along with my box art restoration runner and give me choices of which to run.  This is the first one of the three, and I call it Madcap #2. 

The below pictures show the dis-assembly sequence.

Major damage was limited to one of the posts that holds the top front brace.  These posts are molded into the chassis tub itself and are long and thin, making them susceptible to cracking and damage.  This one broke midway up the post.  You can see the broken post still attached to the brace.

None of the Madcaps I've bought so far have had ball bearings.  Back in 1989, ball bearings were still a luxury for most people, so plastic bearings reigned supreme.

A Reedy ES motor was mounted.  The wind is unknown.  The gray substance to the left of the motor is the foam cover that has disintegrated into dust particles.

The ball differential, another of the Madcap's weaknesses, was in good condition.  Wear was minimal.

I cleaned all of the metal parts using motor cleaner.  The plastic parts were washed in the sink with hot water, dishwashing liquid and an old toothbrush.  After the parts completely dried, the chassis was rebuilt by following the Madcap manual.  Ball bearings were used throughout, and the stock blue friction shocks were replaced with black CVA shocks (50519 and 50520).  The stock soft aluminum 23T pinion was replaced with a Robinson Racing #1123 steel 23T metric (0.6mod) pinion.  The Robinson Racing 11xx series of pinions are highly recommended for 0.6mod purposes due to their high quality machining and strength.

Rebuilding the chassis was uneventful except for the front brace posts.  Attempting to glue the broken front chassis post would never work because it is simply too thin to offer any strength.  In the past I have tried CA glue and epoxy, but the joint never withstands the strain of screwing down the front brace or ultimately gives way while driving.  A very strong repair is available, however, if you are careful.  The post can be completely removed all the way down flush with the bottom of the chassis tub. The length of the original molded-in post is 25mm.  RC4WD sells aluminum links in varying lengths, including 25mm anodized in black.  These links are internally threaded to accept a 3mm machine screw on both ends.  Once the post has been removed and the plastic webbing brace structure cleared, the 25mm aluminum link can be mounted in its place.  This provides a very strong mounting point for the front brace.  Use 3mm washers with the screws on the bottom in order to widen the screw's contact area with the chassis and provide a strong foundation for the post.  I removed both plastic molded-in posts from this chassis and replaced them with the aluminum RC4WD links.  It is very stealth.  Only the space between the plastic ribbing and the post give it away.

A package shot of the RC4WD 25mm black anodized aluminum link with 3mm internal threads (part #Z-S0880).

For the motor, rather than use the Reedy, I decided to install a well-used "Demon Power" brushed motor with reflective red label.  I had gotten it as part of a used motor lot a few years ago.  I figured I'd give it a try to see if it earned its name.  As it turned out, it was not very impressive.  Maybe the magnets are weak due to abuse it received before it came into my possession but I think it barely has more power than a stock RS540 motor and certainly doesn't spin any faster.  I'll keep it in this chassis until it dies or I get bored with it.

Here is Madcap #2 finished. For radio gear, I used an old S28 servo with G to J conversion for steering (it still works perfectly, so why not?), a Futaba MC230CR ESC and a Futaba R113ip 75MHz receiver. 

The wing has seen better days for sure.  It's been reduced to just a curved flat surface by the original owner.

I am using the original body for now because it is in OK shape and is functional even if it isn't concours-worthy.

The wheels and tires are made by Carson Model Sport in the UK.  They are great for 2WD buggies that use ball bearings in the front wheels instead of hex mounts.  The tread design gives good traction and the wear is decent.  I always balance the rear tires to reduce vibration and improve smoothness.