Hints and Tips

Andy Horka's scissors

2013-09-20T03:01:10+00:00

One of the challenges in building custom transmitters is finding the best mechanical components. Lot of systems have been built using donner systems of one kind or another. Another option is to build your own case and gimbals. Perhaps the most challenging part of a gimbal design and fabrication are the centering components. Andy Horka has developed a beautiful set of centering scissors and is making them available. You can see a lot more details on his blog at http://andysrecroomrc.blogspot.com/

If you would like to own a set of these scissors please contact Andy at andyhorka@shaw.ca

Scissor pair $12.99 + $2 Shipping and handling

Tony's building thoughts

2013-09-20T03:00:16+00:00

Hi everyone:

For those of us building or contemplating building a Microstar 2000 transmitter, whether a single stick or a two stick, I have run across a couple of things that you might find useful:

Pushbuttons: I used a snap action pushbutton from Digikey, C&K # 8121, that has a definite snap feel to it. However, the press on plastic button cap does not allow the stem of the switch to fully depress. I sanded 0.030 inches off the bottom of the plastic cap so the stem could be fully depressed. On the other hand, a couple came through with a long stem that I filed down so the plastic cap would not be sticking out too far. Each button cost $7.00 and the caps just a few cents each. The caps are available is several colors but only black were available when I ordered them. I think I like the all black plastic items better than a multicolored array.
LCD: The LCD that came with the encoder kit I bought from Kees had the connection at the end of the unit. This caused me to have to crowd the LCD close to the gimbal making the location unsymmetrical in the space between the gimbal bezel and the edge of the case. Big deal but it bothers me a little. When you order the kit from Kees make sure the LCD has the connector anywhere other than at the end. It was too late for me to switch because I had already cut the opening for the LCD in the front of the case.
LCD Mounting: I tried a couple of approaches to mounting the LCD including a stack of washers to separate the LCD far enough into the case so that the trim window will fit flush to the front of the case. I ended up fabricating a plywood spacer that I sanded down until the LCD was exactly spaced to allow the window to properly fit. I used 2-56 flat head stainless steel screws to hold the LCD in place. I will have to use some kind of glue or silicon to hold the window onto the case. I also placed an insulating piece of plastic at each end to provide support for the nuts rather than have the nuts come in contact directly with the LCD PC board. Any ideas about what to use to attach the window to the case?
Trim and Channel 6 and 7 Control Pots: The best trim and control pots are the ones that are no longer made by Bourns that had the 1/8” shaft with the lock nut that could be adjusted to place drag on the shaft to hold the setting. I placed a small but very stiff compression spring on the pot shaft between the pot and the pot mount to apply drag. It feels OK but a better way might be available if some of you put your thinking caps on. For the rudder trim and channel 6 and 7 controls I used plastic units I scavenged from some of the eBay parts transmitters I bought. I took them apart to clean and lubricate them with some Ace pot lubricant I still had. The wafers and wipers looked very good probably because they are not cycled as much as the primary controls.
Restoring the Case: I had to fill a bunch of drilled holes and slots that were in the case. I filed a bevel on both sides of the slots and slightly countersunk both sides of the holes so that the epoxy filler would not fall out if the bond ever failed. I attempted to duplicate the bumpy surface of the surrounding vinyl by cutting a piece of another old transmitter case and clamping it to the case. I placed the epoxy from the inside just enough to fill the opening. Unfortunately, the epoxy ran out from under the clamped piece of old case and it would not come off. I had to very carefully sand off the excess and then file down the excess from the inside of the case until it was flush. What worked better was to back up the holes with a piece of masking tape. The tape prevented the epoxy from spreading out onto the outer vinyl surface but it did not provide the bumpy surface I was trying to achieve. I tried to get a bumpy finish with the vinyl spray color I used but it flowed out smoothly. These spots are not easy to find but if you look closely at some of the pictures I sent in you will spot them.
Finishing the case: I used a vinyl spray from a company called SEM I bought at an automobile paint supply store. It comes in a wide variety of colors. I tested it by applying fuel to it; it is fuel resistant. I used stainless steel 2-56 and 4-40 machine screws I bought from a company called SMALL PARTS INC. Check them out. The screws and nuts I bought in packages of 25 were dirt cheap compared to buying screws from a hobby shop for a couple of bucks for four. I used the flat head screws rather than the typical pan head screws because it looks so much better with all the screw heads flush with the exterior of the case.
Switches: If you look at the recent pictures I sent in you will see that I reduced the length of the toggles on all the toggle switches because I am very concerned that I might accidently hit one unintentionally while flying. It makes them harder to flip but that is what I wanted. I used a Noble switch from another parts transmitter for the Run/Cal switch, rather than a locking SPDT toggle switch because I had an extra and I like the way it looked behind the antenna mount. In the Cal position the switch cover is held open by the pin in the cover. It is easy to tell if the switch is in the Cal or Run position.
The Gimbal: At first I was going to use the World Engines Expert 3 axis plastic gimbal from my old WE transmitter but I damaged the rudder knob trying to get the knob apart to replace the pot wafer. It is one of the best plastic gimbals because the rudder knob is so good and the plastic is fiberglass filled and very stiff. It uses the ½” pot wafers which are as rare as hen’s teeth. Next I was going to use a Kraft 3 axis gimbal I bought on eBay but it had strange pot resistance values. I did, however, scavenge the rudder knob as a spare for my Silver Seven. Next I came across a Royal Omega two stick transmitter with Ace look alike metal gimbals and proceeded to fabricate a hollow stick to hold the Kraft rudder knob, but then Kees dropped a note to us that he found Bourns 6639 pots that have some very good qualities, among which are very smooth feel, low turning torque and extraordinary long life. I bough two to use in the Omega gimbal. Then I found the Proline gimbal that I fitted with some more Bourns 6639 pots on all three axes. It was a tight fit but the rudder pot just fits inside the case without shorting out the pins that stick out the back of the pot. I also made new centering scissors with long spring arms so I could adjust the tension by moving the springs in or out. The sheet metal frame of the gimbal allowed me to mount the aileron and elevator trim pots to it. The one thing I revised was the outer pivot because the stock pivot caused binding. I made a new pivot from a ¼” turned down brass screw that fit precisely in the nylon bushing, but had to float the pivot pin and nuts and washers on epoxy so that the pivot pin lined up exactly with the axis of the elevator pot shaft. The elevator pot held the assembly in alignment while the epoxy hardened. Smooth as silk.
RF Deck: I used the XPS Proffi 4000 RF deck because it is available without the plastic case because I wanted to mount the deck totally inside the transmitter. Access to the bind and program button and view of the LED is through a small hinged hatch. The hinge came from an old Super 8 movie camera and the latch is a miniature hatch latch made by DuBro.

I know that this is a very long post but I hope that some of the trials and tribulations I went through will help those of you building or contemplating building a Microstar 2000 transmitter. If any of this raises questions let me know. I will try to answer all of them. Yes, I now have two metal gimbals, one fitted with Bourns 6639 pots and a Kraft rudder knob with a new CTS cermet pot wafer that I am holding for a spare for my other Ace Silver Seven.

Tony Staten Island.

Dave "The Pipe"'s thoughts

2013-09-20T02:59:15+00:00

A REPLY & Addenda to Tony's post ...

Dear Tony:

The PIPE Here again, and I've got a few (actually, MORE than a few) "replies & addenda items" to supplement that well-detailed document you've started a new posting thread here at our group's own "forum".

My reply is structured just like your initial response, so that everyone reading you initial document can understand exactly what I'm getting at with each comment and response.

Now, to the items you've brought up, and what I've been doing for my own MS2K-based, all-single-stick "knobby radio" projects...

(1) Pushbuttons and their switches: Since I've been purloining my now-retired Ace RC Silver Seven knobby radios for most, if not "all", of the control hardware they've possessed since the 1980-81 timeframe when I first built and started using them on 53 MHz AM, the S-7's pushbuttons are used for the "Preset" (which I call a "coupe" switch, per WW I rotary engine parlance), "AutoTrim" and "Option" switches, and existing spare caps give the coupe switch a black button, the AutoTrim a red button, and the Option switch a white button.

(2) MS2K LCD Display: The pair of "version 3" (or "Mk.III") MS2K, eight memory position encoders that Gordon himself got together for me starting almost a decade ago, use a 2x16 character display that came with the encoder, and isn't backlit, and have connector locations along the long sides of the PC boards that they're built upon.

(3) LCD Mounting: I've used a scratchbuilt, own-design G-10 glass-epoxy mounting "frame" to screw-mount my LCD display board onto, that in turn mates to the inside of the case's front panel using double-sided foam tape that Du-Bro makes for RC gear mounting...it's their #634 foam tape kit, and in their online catalog at http://www.dubro.com/hobby/ecatalog/dubro/00030.htm . The specified bezel in Gordon's parts list, at Digi-Key's page at http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&WT.z_homepage_link=hp_go_button&KeyWords=PRD250LPW-ND&x=26&am! p;y=9 , was mounted to my repurposed Ace MicroPro knobby radio case with Weldwood contact cement, CAREFULLY applied to both the bezel's rear edges, and to the corresponding edges of the case aperture, with a toothpick to prevent the smelly contact cement from "getting out of control" and "stringing" itself all over the place.

(4) Control Pots for Trims & Ch,4, 6 & 7: The Bourns 3852C pots that exist in my trio of ProLine Competition Six knobby radios get used for the Ch.4 throttle controls, with Bourns Model 51 pots used for Ch. 6 & 7 control, all using the "sector"-like control tabs that came from my S-7s. These "sector" tabs all have Du-Bro #139, 1/8th in. wheel collars pressed into their carefully-drilled-out hub areas to "beef up" their ability to be secured to their respective pot shafts. The trims are all the Ace RC 21-step plastic Dunham units, with their stock "discrete" pots for all four "basic" control function trims, with only the throttle trim (on the right side of the joystick opening, mounted to the front panel) needing a Clarostat RV6-style submini pot to take the place of the stock pot in my knobby radio's internal layout, because the original pot connection terminals interfered with the right side control mountings.!

(5) Restoring the Case: I've tried using epoxy to restore, for the short time I was using it again, the case on my #2 S-7 knobby radio to use it again in 2001 before I permamently retired it...it's worked well enough that an MP8K knobby radio I've got, with a possibly good MP8K encoder in it that I've chosen to replace with my own "No.2" MS2K encoder unit instead, will get a classically advertised product named "Liquid Leather" (at http://www.asseenontv.com/prod-pages/LiquidLeatherRepair.html ) used to restore the vinyl cladding over the epoxy-patched areas. The epoxy itself is most likely going to be the oft-recommended JB-Weld kind, as its adherence to metal parts IS hard to beat. Tony's lament at not being able to have an "uneven surface" with his case patching task would be taken care of! with what comes with the Liquid Leather kit, however, as "graining papers" come with it to help hide the patched area's noticeability, and those accessories in the Liquid Leather kit would VERY likely have helped Tony out, with that part of his case restoration!

(6) Finishing the case: The Dupli-Color vinyl spray finishes, on the Web at http://www.duplicolor.com/products/vinyl.html , should they prove to be completely fuel-proof when thoroughly dry, to the FHS Red Max 10% nitro four-stroke fuel I use, would be my pick to do the color with IF I ever chose to give my 50 MHz MS2K knobby radios a "different" color scheme than the ivory vinyl cladding they've already got. I MIGHT do this with Andy Horka's superb choice of Hammond 1455T1601 cases for my eventual second pair of MS2K "knobbies", that will be built from the ground up to use Futaba's TM-8 FASST Tx modules. The Liquid Leather kit has several different colors to allow for rather precise color matches when patching up a vinyl-clad case, and my own pair of upcoming 50 MHz MS2K knobbies, as well as the 2.4 GHz pair of MS2Ks, wil! l all be wearing main placards (the ones surrounding the "main status display" on the front panel) I'm designing here at home in CorelDRAW 12 and Corel Photo-Paint, that feature "MicroStar 2000" lettering using a freely-available version of the "Koloss" font that Ace RC used for their logo (located at http://www.fontspace.com/thomas-e-harvey/coliseum ), and featuring a constant vintage World War I aviation graphic theme based on classic Old Rhinebeck Aerodrome WW I-era aircraft photos as their color backgrounds, for my "Rhinebeck Scale Special" RC radio theme on all my MS2K knobby radios.

(7) Switches: I've already posted up the so-called "Combo Switch" hookup diagram at http://groups.yahoo.com/group/MP8K/photos/album/329764481/pic/596420608/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc , that COMBINES the main power switch and the "Cal-Run" switch into just one, three-position ("OFF-CAL-RUN") locking toggle switch...the best bargain for these nowadays is at http://www.onlinecomponents.com/buy/C-K-COMPONENTS/7411K2ZQE/ ...I recently got FOUR more of these, for all my future planned MS2K knobby radio projec! ts. The flat handle SPDT toggles for the two switchable mixers, and for Channel 5, are C&K units as well - the Ch.8 SPDT three-position switch just uses a regular round bat handle. My dual rate switches are SPDT ROCKER switches, again from my S-7s, and are available as C&K part #7101J16ZQE22 ...these switches can be obtained from the same source as the "combo switches" are, at http://www.onlinecomponents.com/buy/C-K-COMPONENTS/7101J16ZQE22/ .

(8) The Gimbal (and Knob): I planned way ahead of time on this MOST critical issue, in getting a number of BOTH MP8K and ProLine knobby radios starting just over a decade ago. John Eyer's excellent choice of the Bourns 3852A pots for the Ace RC metal gimbal joystick, as a replacement for Ace RC's own joystick pots, is just too good a match for those...now we've got Andy Horka reproducing the Ace RC metal gimbal unit!!! For anyone who's got the all-plastic Kraft/Heathkit rudder knob, or the Dunham all-plastic knob, please remember that the old-style servo pot resistance wafers & wiper assemblies ALWAYS came from military specification "RV6" style subminiature pots. The old Kraft/Heathkit "metal backshell" rudder knob, that had that long machined aluminum rear section to the knob, actually USED a completely intact "RV6" style discrete pot for its resistance unit. When I can eventually get back! to a daytime job, and afford to actually DO it, I'd love to make a new rudder knob design available...it's closely based on the JR Century Seven & PCM 9 knobby radios' rudder knob in dimensions and physical size, and uses a Bourns 3852C pot, which is not very different in dimensions from the Asian-sourced pot that JR used in their rudder knobs two decades ago. The knob I'm working on also is intended to ONLY use corrosion-resistant metal parts (think stainless steel here, even possibly the rudder knob centering spring!) and has all of its unique-design metal parts that need to move, riding on teflon washers and a teflon main bushing for a very smooth rotational feel.

(9) The RF Deck: Where I've been "KA1ABG" for a third of a century now, going for 50 MHz is a no-brainer...Gordon's own 50 MHz synthesized deck is still the best choice for this need, and I simply used the Ace RC antenna mounts from my S-7s, with Futaba's "ANT6", or "FUTM5050", one meter long collapsing antenna for my 50 MHz flying needs, which IS the closest available VHF RC Tx antenna to the old Ace RC units, and even fits the same metric threaded screw that the Ace RC antenna mounts use. For the increasing appeal of SpredSpec 2.4 GHz flying, with that whole band still being in a "semi-experimental state" even now, the good reviews on the Futaba FASST system have got me going for it quite solidly. The TM-8 FASST module simply is the slickest, least complicated 2.4 GHz signal-sending solution I've yet seen, with no...and I mean NO...exposed wires sending the signal into its integral swiveling an! tenna, something which IS present on the Spektrum and XPS units, and which turned me off to those right away, as soon as I spotted it !

Everyone, of course, likes to make their own choices to make on how to build their own MS2K-based RC radio, be it a knobby unit or dual stick Tx, based on what they can get to hook up their encoder with, available control setups, cases, etc...it's just that with Tony's excellent post here to "open up" this thread with, I felt I needed to provide my own accounts on my MS2K-building experiences so far. I'm really looking forward to someday "prototyping" up the new rudder knob, and with Bourns 3852-family pots on ALL three aerodynamic control channels, the "balance" between the elevator, ailerons & rudder is bound to be more equitable...

...now to go back to some more CAD home-based drafting to help all these things along!

Yours Sincerely,

The PIPE at the-pipe@comcast.net ;) !!

A big THANK YOU

2013-09-20T02:58:10+00:00

Hello all,

I just wanted to comment on the great information shared on this site and the MP8K group as well.

I am in the process of building an MK2000 and I find the articles here helpful and motivating.

I wanted to specifically thank Tom Pomeroy for his drawings and personal notes of the Chidgey SS from which I am fabricating my very own copy. Thanks to Andy Horka for the scissors. Having them will definitely speed up the process. I am waiting to get all of the mechanics done before I start on the encoder, RF deck and receiver (Thanks to Kees for the kits). Gordon and everyone else contributing support to the project really encouraged me to go ahead. I am not a professional machinist but I have a well equipped shop. I have worked in the electronics industry (RF) for a little over a quarter century so I’m looking forward to the tweaking part. I was quite excited to see the helicopter update because my ultimate purpose will be to fly helis with a single stick! Without sounding trite, they say “it takes a village to raise a child” well, the MK2000 is maturing and is something everyone in this group can be proud of. I will post pictures when it is completed.

Thanks All,

Brian

N8KTR

p.s. I have to mention Pete Carr for posting his airplane and MK2000 in the MA magazine without which I’d never known of it’s existence.