Electric/35mhz compatability

[Ally D]

Hi there, new to R/C flying, Can anyone tell me if I can use my 35mhz 1980s Futaba gear to work an ESC if I want to convert my glider from Cox 0.49 power to electric/lipo? My LHS said this was not possible as the ESC will interfere with my 35mhz stuff, but obviously electric flight has been on the go since before 2.4 gig gear was around, so whats the craic? Thanks!

[Frank Skilbeck]

You shouldn't have a problem, especially with brushless, I've flown many electric planes on 35 mhz. The ESC will work on any receiver and while 35 mhz is more prone to interference from the electric noise generated by the motor/ESC I only ever experienced this using reduced range, i.e. with shortened aerial, Rx's on some Electric Ducted fan models where the aerial ran alongside the ESC and motor. Keep the RX & aerial away from the motor and ESC and you'll have no problems.

 

We have several electric gliders in our club working on 35 mhz with no problems.

If that's the best advise your LMS can give I'd go to one of the electrical specialists for your powertrain, e.g. Robotbirds, BRC Hobbies, Puffin Models and many others who advertise on here who will give you good advice.

[Tim Hooper]

Posted by Ally D on 04/02/2012 01:16:52:
My LHS said this was not possible as the ESC will interfere with my 35mhz stuff, but obviously electric flight has been on the go since before 2.4 gig gear was around, so whats the craic? Thanks!

 

 

Ally,

 

You've said it yourself. We used 35Mhz for years for e-flight. Many still do.

 

Just keep the ESC a couple of inches away from the Rx and you should be fine. Range check though.

 

tim

[Dave Bran]

I have quite a few EP models on 35MHz, 25 plus. These spread from fast wings through scale and pattern to powered gliders.

 

There is NO inherent barrier, but compared to 2.4GHz (which I also use), you may need to be a little more careful with interference, like for example using ferrite rings on the ESC to Rx wiring, and keeping the two apart as much as possible, however, it's not rocket science and it is practical to combine the two...........your LMS should be ashamed to be saying otherwise!!

 

AND, range check WITH MOTOR RUNNING !!!!

[DH 82A]

Just one thing to note--- with Futaba radio, you will probably need to reverse the throttle movement on the transmitter. Otherwise/ the esc may not programme properly.

[DH 82A]

deleted,  double post

Edited By DH 82A on 04/02/2012 11:36:58

[Peter Beeney]

Ally, - With respect, I don’t want to cover any ground that you may have already looked at, but to supplement the concise and informative posts by Frank and Tim, I would also personally consider having a long hard look at the transmitter. If the battery has been left in and connected since the 1980’s it’s possible that there may be some corrosion set in. This invariably starts in the black (negative) wire, and because this is usually a common connection it quickly travels everywhere, eventually attacking any metallic parts, including the other wires, etc. If there are any signs of it getting onto the printed circuit board with the components on then there’s every chance this could be prone to a sudden failure, at the very least, and Murphy’s Law says it will be when your model is at it’s highest point in the sky!

Also, by the same token, a really good check on the battery capacity would also be high on the agenda, this is again something that can fail without warning.

Apologies if you’ve already sorted this……

PB

[kc]

Peter is absolutely right and the nicad will almost certainly need replacing........check the cost first because sometimes the old different shape nicad packs are so expensive its almost as cheap to buy a new Tx. Local shops probably wont have an old type nicad in stock ( it will be NiMh anyway ). Overlander is one supplier of replacement nicads in various sizes. Check the type of connector in the Tx or whether it's soldered in.

The same black wire warning will apply to the switch harness, maybe the Rx as well.

 

Lots of people use 35Mhz for electric but only electric ducted fan seems any problem.

 

If you do decide to buy new TX & Rx note that some come with switch harness, NiMh and charger while some come as dry battery and without charger and switch harness at the quoted prices!   Also JR and Spektrum chargers use opposite polarity plugs to Futaba, so beware mixing chargers.

Edited By kc on 04/02/2012 12:10:06

Edited By kc on 04/02/2012 12:13:53

[Erfolg]

I suspect that Peter is correct, in the need of a check of some type.

 

I restarted modeling, about 7 years back now.

 

Just like you Ally, I resurrected my Sanwa Clubman and Futaba Gold, both 35. The Sanwa, did not work at all after charging. The Futaba, lasted about 2 weeks, before showing an output on the indicator, yet no signal. I just dumped the Sanwa, the Futaba, just takes up shelf space.

 

With respect to the original issue, all the responders are correct in my opinion, there is no problem with 35. I still use it. I also have two 2.4 sets, in my opinion no better at the practical level than 35. Which is not quite true, I burnt out a inrunner in flight, which resulted in te model going downwards in a fast circular dive. The model did recover. On reflection, I do not think it was the electrical noise, but high current draw, shutting down the ESC, so even then not a 35 issue.

 

I have used 27 in the past with brushed motors with no trouble, other than the standard precautions.

[Ally D]

Wow, thanks so much for all the replies, right here goes...

 

Frank, Tim, and Dave,

 

I thought as much, basically its the ESC that causes interference if any, so as long as I mount it sensibly I should be ok? If that is the case I wonder what the best way to determine what is the best electric set up to use would be? I can't find much about it by googling! The trouble is I'm not too sure on electrics, here's what I know and don't know...

 

I think I need a 3 cell lipo, which I would need a special charger for yes?

 

Brushed or Brushless? What size?

 

Are ESCs made to go with specific radio gear or will anything work? (voltage/connectors etc)- My receiver is a fairly unknown one, called an ACT Micro 6, mated to my 80s Futaba Tx. Does an ESC have its own power supply or does it work off the 4.8v Rx supply?

 

Sorry for all the questions, the book I have used for all the other bits of my build was published before Lipos etc so was a bit out of date.

 

DH 82- I think my Tx has a reverse option for all it's channels, so swapping it shouldn't be a problem.

 

Peter- yeah this is a worry for me, Tx SEEMS to work OK, and no sign of anything sinister in the battery bay/circuitry , but it would be a hell of a way to lose a model you have scratch built- if I'm gonna break it it should at least be because I have crashed it! The Rx battery was shafted when I got the stuff (ebay) so I have replaced that with brand new Ripmax, I think I can get a new square type battery for my trani for around 20 quid, to be honest I was just holding off spending more on my 80s gear til I knew I could go electric- I think it might seriously be worth it for the peace of mind!

 

Cheers guys!

Ally

 

[Ally D]

Thanks Kc and Erfolg, seems like the consensus is to ditch the old Tx battery- looks like you can got them from Ripmax ok I think, does the mAh rating matter so much if the voltage/connections are the same? My new Rx battery works fine with the old stuff?

 

Here's photo to let you see aircraft/ Tx

 

Ally

[kc]

It's essential to use a proper Lipo charger! ESSENTIAL You can read about people burning down their workshop even houses due to Lipo charging.

Your Tx looks like the good old 5L ..........if it was any older the collectors like Ali Snr would want it! I wouldn't waste money on a new nicad ( and I am the meanest, cheapest flier in my club ) If you are new to flying check first with your preferred club and see which Mode they teach on. If your old Tx is on their wrong mode you cannot change the rate switches on the old 5 L as I found when I started with a 5L in 1985. Also there is no buddy lead connection on the 5L Visit the club and ask.

[Trevor Crook]

Ally, welcome to the initially befuddling world of electric flight!

You don't say how big your glider is, but a power set-up of 50 - 70 watts per pound of weight will be about right. So let's assume your glider weighs 2lb, you'll want a 100-150 watt setup.

A 3-cell lipo should be ok, and makes the sums easy, as you can approximate the voltage to 10V. 10V x 10A will give 100W. I'd recommend going for 150W, which would require 15A. You'll want a 20A ESC to avoid stressing things, and a motor that will deliver 15A continuously (you won't be on full throttle much, so this should be fine). The ESC powers itself and the radio gear from the lipo, you won't need an Rx battery.

If you choose a motor that gives 1000-1200 revs/volt (expressed as kV) this should give a sensible prop size of, say, 9 x 4. Unfortunately, the only way to check the current and power is with a wattmeter, which will cost you around £30. Most distributers quote suitable prop sizes for their motors.

You should be able to get a well specced lipo charger for around £30.

I seem to have gone on a bit, so I'll summarise my guesstimated setup:

15A 1000kV brushless outrunner

20A brushless ESC

1500mAH 3s Lipo (20C discharge will be adequate)

Online suppliers will have the keenest prices, but as you'll probably need some help, try another shop if you can. Alternatively, specialists like West London Models wouls be able to advise and supply by phone.

 

Good Luck!

[Pete B]

Might be worth having a look at Component-Shop for a Tx battery - good range of all sorts of useful bits and good service, in my experience.

 

Pete

[Ally D]

Trevor,

The Glider is about 60" span, and weighs 13.4 oz with Rx battery etc all inside. Thanks for your estimate, but perhaps you thought my model was bigger/heavier than the pic suggests?

 

Also a 9" prop sound massive, but maybe that's because I'm used to the little 6x3 on my Cox power pod (yet to be test flown)

 

You say the Rx / ESC is powered by the lipo? Are they not different voltages etc? I thought you would power Rx/ESC with 4.8v battery, then the ESC regulated the supply from the lipo to the motor?

 

Kc, I understand that Lipos need special care- I saw a guy crash his model at my local club when I was checking it out- the Lipos were up in smoke within seconds of impact!

 

Ally

[Ally D]

Thanks Pete, looks like a great site- also seems a good source of chargers and things.

 

Will any 9.6 Tx battery work providing it has the right connections? I see batteries on Ripmax/ebay etc that LOOK right, but I don't want to blow anything up!

 

Ally

[Trevor Crook]

Ally

 

For some reason I didn't see the photo!

 

For that weight, a sub-100W setup should be fine. You can get cheap outrunners known as "bell" motors (because the case looks like a bicycle bell) and one of these should be fine. The prop will be bigger than the Cox one, as it won't be revving as high. So I'll revise the setup to:

Brushless bell motor, 10-12A continuous rating

15A ESC

1000mAH - 1300mAH 3s Lipo

 

The ESC contains something called a Voltage Regulator, that takes in the Lipo voltage and converts it to 5V for its own electronics and the receiver and servos. You just plug the ESC into the throttle channel, and it feeds the 5V down two of the three wires going to the Rx socket. Hence, nothing is plugged into the Rx battery connector.

 

Nearly forgot, whichever motor you get, you'll need an appropriate prop adaptor.

 

With this set-up, try a 7 x 4 or 8 x 4 prop - it will depend on the motor's kV.

[kc]

The Tx nicads are either modern flat or older square packs, The other difference is the connectors, some were soldered into the Tx, some had a plug, some had a stud type connector which pressed onto contacts ( these are the ones that are now rare and expensive I think ) While some 5L etc had the battery box intended for dry cells which are sometimes fitted with individual AA nicads. These can give an intermittant connection which is death to your model. Stud types can corrode and be dodgy connections too with the same wrecked model possibility.

All the above can vary depending on whether the Tx was bought as an Futaba nicad set or bought as dry battery & converted by the shop or at home to take the cheaper non Futaba nicads which was most common in the 80's.

The capacity is increased nowadays but your charger should work even if it needs extra hours.

So if you have sufficient soldering skills any type could be replaced if the wires are not corroded.

 

Another point is what is the history of the Rx and it's crystals? Has it ever been crashed?

Any doubts would make it better to buy new radio.

[Ally D]

Cheers Trevor that's all good info- and I find the bit about the Lipo powering the Rx via the ESC fascinating- You have pretty much cleared all that up for me!!! Now I will at least know what to look for when comparing prices etc.

 

Kc- Don't know the history, all I know that my receiver took a hit when I gave my glider a hard landing on it's maiden flight- but i had wrapped EVERYTHING in lots of foam, so it was pretty well protected and still works with good range. If need be I will replace my battery in my Tx, but no new gear yet- if I do buy new stuff it will be 2.4 gig, and something that will last a long time. I will just have to wing it with the 35mhz stuff for now!

 

Ally

[Frank Skilbeck]

Just for info, I've just put together an electric glider with a 1100 kv motor, 7 x 6 prop and 3s lipo, pulls just over 10 amps and hence just over 100 watts, flies a the 750g (26 ozs) model very easily, so that could be a good starting point for you.

 

1100 kv motor which can take upto 15A

20A ESC (always good to have some good head room)

1500 to 2200mah 3s lipo (depending on how much room you have)

 

Have a look around the various mail order suppliers that advertise on here and you will find something that fits the model and your pocket.

 

Make sure you do a range check with the aerial down and the motor running

[ken anderson.]

ally D ... the only times i've had a prob with 35mhz/electric is when using EDF'S.......the rest of the time......no probs...

 

ken anderson ne...1.... 35mhz dept...

[fly boy3]

A range check has been recommended with ariel down and motor running, if this is done off the patch can I leave the prop off, or will this interfere with the test. Cheers

[Trevor Crook]

Useful info, Frank - not too far from my guesstimate.

 

Ally, Frank has made a good point on the Lipo size - if your fuselage can take a bigger pack, it will give you extra flight time, without too much of a weight or cost penalty.

 

Something I forgot to mention is that the ESC will automatically cut power to the motor when the Lipo gets low, but still power the radio, so you'll still be safe to glide in and land. It's best to time your flight to avoid this, though, which you'll be able to do once you are familiar with the flight time you get for a given battery drain.

[fly boy3]

Hi Ally, nice looking model and a good covering job. The name of the model suggests that you live in Perthshire, ? Could be wrong. LoL

[Ally D]

Cheers Frank, now I have an idea of what to shop online for then I can seek out a good deal! I smashed my glider up pretty bad this morning, wasn't a particularly rough landing, but the fuse just aint strong enough to survive the weight of the Rx battery inside it. I was so scared of making the thing overweight I seem to have drastically under engineered the fuselage, luckily my wing has come out unscathed- the time consuming part! I am gonna build a new fuse to take electric power, dispense with the Cox power pod (messy, fiddly, unreliable) and just stick a motor in the nose with a folding prop. Electric is the way to go! My local model shop has lipo chargers, between 30 and 50 quid, are they all really this dear? Surely there must be a cheaper alternative for smaller less fancy models etc? Also, what wingspan was your 26oz model?

 

Ally