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.