Shaun Walsh

There's probably a small but lucrative market for Tungsten spinners!

A while ago I had reason to take the motor off my Riot following unplanned contact with terra firma which meant that I had to straighten out the motor mount. I noted that washers were used to give down thrust and right thrust and made sure that they went back in the same position. The Riot flies straight and level with no tendency to climb on powering up so I guess the designer got the angles right.

It made it onto Sunday's best tv in the Guardian, described it as "Robot Wars with Nazis!

Posted by Mike Blandford on 09/09/2018 14:40:32: Posted by Focae on 09/09/2018 10:05:14: Mike, the output current can never exceed input current. A certain gentleman named Kirchoff determined that in one of his Electrical Laws. ‘The sum of the output currents must equal the input current’. You will also never have the same current in two legs of the motor wiring. Outrunner motors are essentially three phase ac motors. The rotating field is created my rapidly switching dc to the legs in turn. The voltage and therefore current in these legs will never be instantly at the dc voltage because the motor windings, being inductors will cause the voltage to rise relatively slowly creating a sinusoidal wave in each leg. Because the windings are 120 degrees apart, you never have all of the current in one leg being opposed by an equal and opposite current in another and you can never have all of the current flowing in one leg. Also consider this, how thick are the wires that form the winding? They are essentially just a continuation of the wires that connect them to the esc. If you did have all off the current flowing in one leg for longer than the ‘average’ switched time, the smoke escapes, usually at the winding because it is thinner than its supply wires. "the output current can never exceed input current" No, but there are capacitors on the ESC input that provide the "extra" current for the current pulses. "Outrunner motors are essentially three phase ac motors" No, they are DC motors with electronic commutation. The ESC connects one of the three motor wires to the positive supply, a second to the negative supply and reads the induced voltage on the third wire to time the commutation. Yes, the inductance will limit the current rise, but actually sufficiently slowly that the current is essentially constant. "you never have all of the current in one leg being opposed by an equal and opposite current in another" Yes you do as it is a DC motor, I just described how the commutation is done. "how thick are the wires that form the winding?" About the same thickness as the wires from the ESC. You may look at the windings and see quite thin enammelled wires, but, for ease of winding and to get more copper in place, the windings are made of multiple, parallel thin wires. Mike I thought it was a simple question, obviously I was wrong

"high revs with nitro and no silencer" Ahhh I remember those days, open exhausts or venturi "silencers" and high nitro fuels, never did me any harm, I said "IT NEVER DID ME ANY HARM" , what do you mean don't shout, I'm not shouting, you're whispering. Seriously I wonder how much hearing loss is associated with being too close to screaming engines back in the 60s and 70s, sorry, this is seriously off topic, I shall stop now.

Posted by PatMc on 09/09/2018 12:17:12: Shaun, if you wanted to use a tractor 7" prop you could use 4s lipo to increase the power by 33% over the 3s figure. I'm fairly certain that the current would still be inside the motor limit on a 7x4 & that it would give higher rpm than an OS10 on the same size prop. A Graphene 4s 1500 weighs about the same as a 3s 2200 so the cg wouln't be changed. Downside is that the rpm would almost certainly be too high for safe use of a folding prop. However even with a fixed prop the overall drag from the pod/motor/prop combo would be less than the same with an OS10. And of course fixed props are a lot cheaper than folders. If going this route my preference would be an ic 7x4 or 7x6 depending on the current draw. Incidentaly I think the OS Max10 was contemporary with the Cumulus not the OS 10FSR which means that the ic power would have been nearer to 120W than to 200W. That's a good point Pat, I hadn't thought about increasing battery voltage to reduce required prop size. However there are just two problems, I have a supply of 3S 2200 lipos and the club I belong to, as well as being silent flight only, limits batteries to maximum of 3S, not entirely sure why (only been a member for a year, not good form to join and immediately start questioning the rules) but we fly from the local school playing fields and one boundary is formed by a road with houses the other side so presumably it's an issue of potential noise complaints (thinking 6S powered EDF jets) and limiting model mass/velocity in the case of an uncontrolled excursion beyond the boundary. The only output data I could find rated all the OS 10s the same as about 200W, if the original design was for a glow engine of around 120 W that gives me hope that it should fly reasonably well, certainly the one in the video link seems happy on 200W.

Thanks for the reply Pat, Ideally I want to try to keep the Cumulus looking as original as possible so no cutting the nose off to fit a motor , I have a classic VW Type 3 in original condition and when I see what some people do to classic Beetles it makes me shudder inside. If it wasn't for the fact that our site is silent flight only it would be getting an OS10 on the pylon (perhaps with a micro servo operating the throttle). I contemplated installing the 1400 Kv motor as a tractor with a standard 7x4 prop (definitely no room for an 8" tractor prop) but decided that an 8" would be better and therefore it had to be a pusher and if I mount the motor over the COG I should be able to add or remove the pylon without needing to mess around with adding or removing weight from the nose it also means I can use a folding prop to reduce drag.. It proved remarkably easy to get everything in the cockpit, 2 small servos at the back with the ESC beneath them, I had to remove the front stiffener and install a battery tray for the lipo and the receiver takes up no space at all with the canopy on you wouldn't know it wasn't full of 1970s 27MHz electronics apart from the lack of a visible aerial. All I need now is the time to finish it, roll on retirement!

Oh, and the motor will be used to climb then glide and the capability to go around again when I inevitably mess up a landing approach

Posted by PatMc on 07/09/2018 21:19:50: Posted by Shaun Walsh on 07/09/2018 11:13:43: Will go for 12 AWG then. The 40A is the short burst rating, its rated for 30A continuous also cooling is not fantastic so didn't want it to get too hot. Shaun, I think the realistic max continuous current for this motor is more like 15A - 18A. The product description rates it at 205W, which presumably will be when using 3s. IMO a 25A ESC would be adequate & any extension wires need only match those already on the ESC. A few questions - what model do you have ? What's the size prop does the clearance allow ? Do you intend only flying it with the power pod or will you be flying it off a tow line/bungee or slope soaring as ? If only flying with the power pod will it be on continuous/most of the time or to gain altitude then glide only ? What size battery will you be using - capacity & cell count ? Hi Pat In reply to your questions; The model is a Graupner Cumulus 2800 from the 1970s, I recently managed to get hold of a genuine unused Graupner motor pod kit from eBay. The motor specified with the kit is an OS10 which puts out about 200W and uses a 7x4 prop. On YouTube there is a video of an electric converted Cumulus, the person who posted it kindly provided some information on motor etc. https://www.youtube.com/watch?v=fFnHcy4eRPA Regarding prop clearance, there should definitely be clearance for a 7" prop and if set up as per the video in pusher configuration with the motor above the COG there will probably be clearance for an 8" prop. I have 2 motors I could use, one is the 1400Kv in the link posted above which would be used if there is only clearance for a 7" prop, the other is a 1000Kv motor which i could use if there is room for an 8" prop both are nominally 200W. The power pod is removable , just unplug the wings disconnect the motor and it should come right off if i want to slope or bungee launch (I originally flew it off a bungee or a winch in the 1970s). The battery is a Turnigy Graphene 3S 2200, it fits in the nose after a bit of minor surgery and the COG is spot on with it in, all up weight is 1300g without motor and pod, as per the original design weight makes you realise how much lighter modern rc gear is.

Buxton Mountain Rescue are training for CAA accreditation to use drones. http://www.buxtonmountainrescue.org.uk/news-articles/another-lodge-shows-its-support

Will go for 12 AWG then. The 40A is the short burst rating, its rated for 30A continuous also cooling is not fantastic so didn't want it to get too hot.

That was my initial thought, I am using an ESC rated to 40A burst current so presumably the wiring is sized to for that, just wondering if I could get away with something a bit thinner as I have to drill a hole for the wiring to pass through in a moulded nylon fuselage and wanted to keep it as small as possible. I guess it' best to play safe and use either the same gauge as fitted to the ESC or the motor whichever is thinner

I intend to add an electric power pod to a glider using this motor https://hobbyking.com/en_us/d2826-10-1400kv-brushless-motor.html The question is, what gauge wire do I need to connect it to the ESC? Thanks

I did wonder about putting the undercarriage on backwards but thought it might move the wheels too far back and increase the tendency to nose over on landing, alternatively I suppose you could insert a couple of wedges under the front edge of the undercarriage to rake it back a bit. Does anyone know if the wing servos line up with the wheels like they do on the Riot, had to tape over mine to stop them getting soaked when flying from wet grass.

Steve Webb gets my vote too, I think business rates put paid to model shops in Manchester

Up to 4 channel use spektrum receivers. I am using 6 channel lemon receivers in a couple of electric gliders and providing you hot glue the micro din aerial leads onto the sockets they work fine. I had a problem with hobbyking orange receivers, even though it was within the stated voltage range I fried 2 by connecting them to a 2 s lipo.

I did wonder if the pushrods on the tailplane and rudder of the Riot were up to the job, they do seem a bit thin. Wonder if the ones on the Ruckus are any more robust?

Posted by Mike T on 23/08/2018 11:06:19: IIRC it's significantly more expensive than the Riot and I can't see why... The manufacturers are probably front-loading the cost of the new moulds to ensure that they don't make a loss if it doesn't prove popular. The Riot has been around a while so the moulds for that have probably been paid for a while ago so you can afford to keep the price lower.

Not sure how much of the Riot tooling is reused, it looks like just the fin, rudder, tailplane and cowling, Wings and fuselage are different size/design. I dare say the motor and servos are common. Just hope the battery bay is bigger than on the Riot, it took a bit of surgery to fit a 2200 3S lipo in mine.

Well I have attached the supplied hook in the position it was designed for (glues onto an internal ply plate) and I would say it's more like 45 degrees from the vertical. 30 degrees from the vertical takes you into the landing wheel well. Just have to try it and see how it goes. Thanks for the help.

Also, those servo dimensions are pretty close to current standard size servos approx 40mmx 20mm with 10mm between fixing holes. Alternatively drop down to something smaller like the spektrum A5040 and add ply filler plates to the current mounts. I am refurbishing a 1970s Graupner Cumulus and was originally going to use standard servos but when i looked at the available space it was so much easier to fit smaller ones and they still have plenty of torque for the application. Unless you are very fortunate you will probably need to make new pushrods anyway so changing size shouldn't cause too much extra hassle, I replace my balsa pushrods with ones made from carbon fibre tube. I read somewhere that Savox servos can sometimes cause brown outs with Spektrum receivers, don't know if this is an urban myth as I have only used Spektum servos.

Hi Tosh Give Steve Webb models a call about the servo, also online as servo shop, they should be able to help. Regarding receivers, if you only need up to 4 channels then spektrum aren't expensive and I recommend them. I have tried orange receivers from hobbyking but fried 2 by connecting them to a 2s lipo despite them being sold as suitable for the voltage, to be fair hobbyking gave me an immediate refund without asking for the receivers to be returned which makes me think its not an unknown problem. I am currently using a 6 channel lemon receiver in a motor glider with flaps because it was easier to fit as it has end servo pins. It works fine with my spektrum dx6, but the diversity antennae are attached with micro din connectors which disconnect easily as I found out on the first range check when I got no further than 6 feet before everything went haywire, on checking both antennae had popped off, five minutes work with a hot melt glue gun sorted that out and range is at least as good as the spektrum equivalent.

Thanks John This may be a silly question but is that 30 degrees from the horizontal or vertical?

I have a BFG 1600 which I normally fly using the front electric motor, however it was supplied with a plywood hook that fits into the bottom of the fuselage. I was thinking of having a go at bungee launching it (I haven't flown off a bungee since 1977), however the hook looks a bit far forward of the CoG for a good launch. Has anyone tried this with a BFG 1600? Alternatively how far forward can the hook be and still get a decent launch?

Hi Chris Sounds like your local club is a good one, enjoy the adventure, I know i am. What i want to know is why doesn't the trainee transmitter of the buddy box pair come equipped with shammy leather grips to absorb the sweat from your palms? One of life's great mysteries.