Steve Hargreaves - Moderator Posted December 28, 2013 Share Posted December 28, 2013 Matt....I've no idea if they are copies...they do look a bit Powerbox-y though don't they? As I understand it they provide a steady 5V suppy to both Rx & servos & supply the servo power direct to servos rather than through the Rx tracks......which seems a good idea to me... But I do take your point.....if this unit fails you lose the aircraft...simple as that. Its a tough decision isn't it.... Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted December 28, 2013 Share Posted December 28, 2013 John, it's more a question of personal choice. I've known some people who have had planes this size and thought nothing of using an 800mAh 4 cell NiCad For me once you get to this size you need a reliable and consistent power supply, the potential damage if you lose control could be significant not to mention your loss in money and time invested. Having a dual power supply gives some redundancy and on models this size you can carry the weight of an additional battery quite easily. There's also the consideration that models this size will be using more/bigger/high current servos. I use these: **LINK**. The use of an electronic switch further improves reliability but all the power is still going through the receiver. I *think* the ones Steve linked to power the servos directly, great for turbines and really big models but unnecessary for a 30cc one in my view, If it was me I'd use the switch I linked to and 2 x 1200-1500mAh LiPo's. That's not to say it's right though, as I said a lot is personal preference. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 28, 2013 Share Posted December 28, 2013 Certainly the reputation of Powerbox stuff is excellent. I'd buy & fit anything by Powerbox with great confidence. Interested in your view that is OK for all the servo power to go through the Rx Matt.....I wonder what the limits actually are for the servo current through the Rx. I've no idea myself I've not owned anything beyond a 15cc model but I am considering something a bit bigger & this is an area of concern to me.......maybe I worry too much... Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted December 28, 2013 Share Posted December 28, 2013 Steve, agree that it's always worth erring on the side of caution. There's no clear cut rule for what's appropriate as the number or servos, type of servo, additional drain of poor linkage set up etc just can't be known for all scenarios. Even the type of model and flying style have an impact, a 50cc 3D with large control surfaces that are constantly moving through large deflections will need more power that a 50cc WW1 bipe. I've got a couple of 26cc size models with one LiPo and a regulator, had an 80cc Su-26 that was running dual power supplies. If I went bigger I'd look at something like you linked to. Each to their own and all that Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted December 28, 2013 Author Share Posted December 28, 2013 thanks matt I cant find that switch you linked to , would I have to order it from america as per your link . Steve I dont think you worry too much , is there no info anywhere on the servo current through the rx ? Quote Link to comment Share on other sites More sharing options...
Rich too Posted December 28, 2013 Share Posted December 28, 2013 Why not go with the manufacturers recommendations? I have used two switches and batteries in the past, as I understand that these are the common source of failures (the switches). Never heard of too much current running through the receiver... Rich Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 28, 2013 Share Posted December 28, 2013 Thats true Rich isn't it....you never hear someone say "I burnt my Rx out because the servos drew too much current".... The actual current taken by servos is very hard to define....I know Tim Makey did a bit of experimentation & showed that servos don't really take very much current at all in use. Indeed my own "experiments" in monitoring how much charge the Rx battery takes after a few flights would indicate that a typical servo is taking much less than 100mA average. On a small ish model admittedly.... The most current I have ever seen was by waggling ALL the surfaces on my Wot 5 from end to end. This has 7 servos & the total current drawn was just over 2.5A.....true there was no air pressure on the surfaces but you'd NEVER fly a model moving the sticks from corner to cormer all the time...... So maybe I Do worry too much......and yet..... Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted December 28, 2013 Share Posted December 28, 2013 this has come up quite alot recently , i have said before i use these **LINK** and these**LINK** seems when you shell out on decent engines /motors . servos and airframes seems silly to risk them with a small rx. ive just got 4 servos which stall at 6amps draw plus a rudder thats similar, then throttle choke servos too, wouldnt even considera standard rx...fly low Edited By ben goodfellow 1 on 28/12/2013 13:17:35 Edited By ben goodfellow 1 on 28/12/2013 13:18:11 Quote Link to comment Share on other sites More sharing options...
Rich too Posted December 28, 2013 Share Posted December 28, 2013 how much?!! I would need a top end model to justify that sort of money people complain about paying £50 for receivers.... Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted December 28, 2013 Author Share Posted December 28, 2013 Woah thats expensive , would I really need to go that far ? Maybe if I had something with a radial moki in for example , I could then justify £245 for a receiver . Quote Link to comment Share on other sites More sharing options...
Rich too Posted December 28, 2013 Share Posted December 28, 2013 exactly, that's way overkill imho.. John, personally I would just go with twin batteries/switches.... Quote Link to comment Share on other sites More sharing options...
Rich too Posted December 28, 2013 Share Posted December 28, 2013 this is interesting (see section 4) **LINK** Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted December 28, 2013 Share Posted December 28, 2013 john , rich . i dont like really sying how much for this and how much for that , but if some one spends xxx on a an airframe xxx on servos xxx on an engine ,,then for a decent rx its not out of the way , ,a 30 cc sbach wont be cheap to set up and , you could spend what ever but if the rx gives in its curtains ,, by the way xxx =alot BELEIVE ME Edited By ben goodfellow 1 on 28/12/2013 17:00:29 Edited By ben goodfellow 1 on 28/12/2013 17:01:10 Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted December 28, 2013 Author Share Posted December 28, 2013 dont get me wrong ben , I totally undetand what you and agree with you up to a certain point . if there were any reports of receivers packing in on a frequent basis in these models the I would definately consider the expense . Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted December 28, 2013 Share Posted December 28, 2013 John, the link I posted is for a UK company, there are others too.Oh, and that Spektrum system, no amount of money would make me put that stuff in one of my airframes. Ive watched big stuff go in, have brown outs and models lost because of failed binds. 2 seconds on google tells you all you need to know. They've even named it Spektrumitis. Quote Link to comment Share on other sites More sharing options...
Rich too Posted December 28, 2013 Share Posted December 28, 2013 this looks useful **LINK** you cannot be too safe I admit, but as a minimum (as I said before) I tend to go with the manufacturers recommended setup. Quote Link to comment Share on other sites More sharing options...
Mark a Posted December 28, 2013 Share Posted December 28, 2013 Posted by Matt Jones on 28/12/2013 17:31:37: John, the link I posted is for a UK company, there are others too. Oh, and that Spektrum system, no amount of money would make me put that stuff in one of my airframes. Ive watched big stuff go in, have brown outs and models lost because of failed binds. 2 seconds on google tells you all you need to know. They've even named it Spektrumitis. Spektrum is what I've used since I started flying and I've had no problems with the genuine stuff. Had an issue with a fake receiver this time last year that cost my Acro wot. Quote Link to comment Share on other sites More sharing options...
Rich too Posted December 28, 2013 Share Posted December 28, 2013 "A note on Parallel/Redundant pack systems: most giant scale modelers have way too much building time and money involved in their airplanes to take a chance on a failed battery or switch. While some modelers prefer a ‘battery backer’ or other ‘device’ to isolate the two packs, Steve notes that the issue that is most likely to put the aircraft at risk is vibration and shock wear and resultant switch component/contact failure or pack strap weld breakdown. Steve says intermittent connectors and switches kill planes routinely— not mythically ‘shorted while in flight’ battery cells. A simple parallel pack system works, has for decades..........." extract from here: **LINK** I also came across an Australian site where they carried out a survey and the majority of giant scale modellers used a single standard rx with twin battery setup.... Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted December 28, 2013 Share Posted December 28, 2013 you could put 2 generators and 2 super duper swiches, but its the rx powerbus that will fail in the event of high drain thats what these systems are designed to get round , the bigger the battery and servos the more risk you have .. do y0u ever have a 4s lipo a big outrunner then a little 25 amp esc .. i think not Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted December 28, 2013 Share Posted December 28, 2013 my flying pal has the 50cc version of this sbach flys well . he told me they are made by yt int... not sure on that . but like i say they look and fy well... Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted December 31, 2013 Author Share Posted December 31, 2013 well I've settled on one of these , havent actually ordered it yet , I just want to pass it by you guys first for your opinions **LINK** Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 31, 2013 Share Posted December 31, 2013 That's the one Matt Jones linked to earlier I think John.....I have no experience with this size of model so I'm not going to comment further....I'll leave that to "those who know"... What batteries are you planning to use with it John?? Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted December 31, 2013 Author Share Posted December 31, 2013 not sure steve , maybe life packs , again I'm open to experience , suggestions , and opinions Quote Link to comment Share on other sites More sharing options...
john melia 1 Posted December 31, 2013 Author Share Posted December 31, 2013 I have now ordered the powerbox sensor direct from powerbox.com worked out cheaper than ordering it from the uk , grand total of 95 euros , hope its worth it , seems expensive for what ti is , ah well no use doubting now is it . Quote Link to comment Share on other sites More sharing options...
ben goodfellow 1 Posted December 31, 2013 Share Posted December 31, 2013 what servos you running in it john Quote Link to comment Share on other sites More sharing options...
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