Chris Bott - Moderator Posted March 15, 2012 Share Posted March 15, 2012 I'm thinking very much like Steve, Mike. That block sitting on the desk could well be the shunt that makes the meter into a 50A meter. Without it the meter may pop before you know it... Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 15, 2012 Author Share Posted March 15, 2012 A DC Shunt it is ----it looks nothing like those we used at school and college and of course there was no paperwork to describe the kit,but there was a small stamping on the device to indicate 50amps DC. I will have to send my certificates back to the college and resign from the institute! I have carried out the test and as you guys have guessed the current demand with a 12 volt battery pack is too high. The motor current exceeds 15 amps with a very low throttle setting and if you blip full power then the ammeter jumps up to 40 amps and beyond. Thankfully no damage has been done. Just out of curiousity I connected a somewhat discharged 9.6 volt pack to the plane and with less than full throttle the motor current exceeded 20 amps,which is two amps above the speed controller rating. As you can imagine this is a very disappointing outcome and I wonder to what degree a smaller propeller would improve /resolve the issue?----but then would it be big enough to fly the Matador? The cheap solution is the ASP 15, the more expensive is the Brushless motor and Lipos---I will give it some thought. MJE Edited By Mike Etheridge 1 on 15/03/2012 14:40:25 Edited By Mike Etheridge 1 on 15/03/2012 14:44:12 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 15, 2012 Share Posted March 15, 2012 40 amps....blimey Mike....your motor would have been a blob of molten metal in no time!!! I'm impressed by the ability of the batteries to supply such a current though.... The 20A out of a discharged 9.6V battery is intruiging too...higher than I would have expected......what does the set up pull with no prop attached.....might there be some resistance in the gearbox?? If the set up pulls 20A off a 9.6V battery then that should be enough to fly it.....what is the draft from the prop like? Should be fairly impressive I would have thought.... Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 15, 2012 Author Share Posted March 15, 2012 Steve, The meter is still connected to the plane so I can carry out tests without a prop. The batteries in both packs are described as 'racing batteries' as I assume they are intended for model cars? Yes there must be some power loss with the gearbox and friction within the set up ---total power in motors was always described as 'useful power + motor losses', i.e windage and friction as I remember it. We already know that the 9.6 volt batteries do not produce sufficient thrust for the earlier flight test---of course the propellor draft with the 9.6 volt pack is inadequate compared to the 12 volt pack.. MJE Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 15, 2012 Share Posted March 15, 2012 ALL batteries are described as "racing batteries" in my experience Mike.....its a bit like the word "Turbo" being applied to hair dryers & vacuum cleaners......its a Marketing term rather than an Engineering term I guess if they were marked "Pedestrian batteries" they probably wouldn't sell very well.... Well I'm confused now then......you say your 9.6V packs are supplying 20A to the motor but theres still not enough power there to fly......something is wrong then....where is that 20A going? Thats a lot of power you are putting into the system.....nigh on 200watts.....& getting very little out....there must be significant mechanical losses in the motor/gearbox.....has a bearing collapsed or siezed?? Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 15, 2012 Author Share Posted March 15, 2012 Steve, if you consider that the motor has not really been used since I bought it in November 2003 then it seems unlikely there is a bearing problem. It has only been fitted to the Matador from new. I have just done a 12 volt test with no prop and full speed / throttle equates to no more than 4 amps. MJE Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 15, 2012 Share Posted March 15, 2012 Thats about what I would have expected Mike...maybe a fraction higher......it shows why brushed motors & gearboxes went the way of the Dodo...thats 50watts of power doing absolutely nothing...(apart from over coming mechanical friction......) Still it seems odd.....you are sinking nearly 200watts into it & don't have enough thrust to fly a 2lb model.....I'm struggling to find a suitable to word to describe it....well suitable to post here anyway... Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 15, 2012 Author Share Posted March 15, 2012 Don't worry about the missing word I have thought of plenty!!!! MJE Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 15, 2012 Share Posted March 15, 2012 Your call then Mike,,,,,,is it to be the ASP or will you delve deeper into the sparky side with a nice brushless 'n' LiPo set up?? Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 15, 2012 Author Share Posted March 15, 2012 Well at the moment I am just thinking of 'sending the boys round' to Galaxy models with the following kit that has proved useless-I still have the boxes (2003 prices indicated): 1 no Robbe propeller coupling at : £4.95 1 no. Graupner 'Speed' 400 FG 1,5 geared motor at : £21.00 1 no. Kontronic Sun 1000 Speed controller at : £18.95 1 no Graupner 8x4 slim prop at: £3.99 1no.Ripmax 8.4 v 500mAh flight pack at: £25.99 TOTAL: £74.88 Once the boys have sorted them out they should return with suitable exchange goods including brushless motor and speed controller !!!! MJE Edited By Mike Etheridge 1 on 15/03/2012 20:28:39 Edited By Mike Etheridge 1 on 15/03/2012 20:33:56 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 16, 2012 Share Posted March 16, 2012 Ouch.....not cheap Mike....plus your 12 volt battery & 50A ammeter.....a tidy sum.... Is the future brushless then? I still think there is something wrong here......many people have successfully flown models with these geared motors...alas I am not one of them so I am a something of a loss here..... Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 16, 2012 Author Share Posted March 16, 2012 Steve, Yes with the additional costs of battery and ammeter so far this experiment has cost just in excess of £100, a sum of money you can buy a complete second hand working RC plane with! In terms of 'value for money' I have only witnessed one flight of this plane when it was first constructed 35 years ago as I described before. For the last 9 years it has cost me over £10 per annum for no flights! Compare that to my Junior 60 that has flown on and off for 50 years at Epsom Downs, High Wycombe,Grantham,South Norwood Sewage Works site and Bartons Point Sheerness. It cost me about £10.00 from new in 1962. (The kit was 58 shillings---less than today's sandwiches!) What I have to do with the Matador is prove that it can fly without investing too much extra money. just a short flight will do. I have all the kit I need to install the ASP engine apart from an RC carb. The installtion of a brushless motor appears to be less work/ modification than the fitting of the ASP though. As you suggest we could well be missing something with the Graupner geared motor. Having looked on the box yesterday evening it suggests that you can use up to nine cells to power it so I could omit one cell from the 12 volt pack and stay within that parameter. No mention is made on the motor of the maximum operating current although this must be know by somebody? I just wonder if a propellor change coupled with a larger capacity speed controller might do the trick.? Edited By Mike Etheridge 1 on 16/03/2012 12:10:18 Edited By Mike Etheridge 1 on 16/03/2012 12:11:18 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 16, 2012 Share Posted March 16, 2012 Well I hate to rub salt into the wound but I reckon you could have got a brushless motor & ESC that would have flown the Matty for less than £20 using your NiMH cells....add a Lipo battery for around another tenner...true you would then need a Lipo charger......another 20-25 quid or so.... So I guess the question still remains.....are you keen to go electric or just to prove that the Matty will fly? Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 16, 2012 Author Share Posted March 16, 2012 Steve, I think you are right similar thoughts have passed through my mind and having looked on Avicraft's website they do bracket mount devices for brushless motors that look as if they can be fitted to engine bearers. The only problem is that the top cowling would have to be reduced though. I might nip over to Bromley this afternoon with the Matty under my coat and get the experts in Avicraft to assist---they will always sell you something! MJE Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 16, 2012 Share Posted March 16, 2012 Good luck.....!! A classic way of mounting an outrunner motor is to use lengths of threaded studding screwed into captive nuts in the firewall.....this can work very well & might be worth considering.... Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 16, 2012 Share Posted March 16, 2012 For example.... Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 16, 2012 Author Share Posted March 16, 2012 Thanks Danny and Steve----I have not seen the studding/ motor mounting method before. MJE Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 16, 2012 Share Posted March 16, 2012 From a quick flick through the thread to see if I could throw in some cheeky advice to fit a proper oily thing at the front (I see you've already considered it) my first thought would be to check the calibration of your meter - even though the shunt is marked as a 50A one. The meter movement will only be measuring milliamps so any small extra resistance in the shunt connectors may result in a large error on the meter. Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 16, 2012 Author Share Posted March 16, 2012 Martin, I well remember at school that all meters were sent away for calibration by the lab technicians I think on an annual basis. We also used Weston standard cells I think with our experiments, its a long while ago 1963/4/5. It did occur to me that I had no way of checking the calibration of the Chinese meter and I bet most serious electric modellers have more than one meter to at least make comparisons of readings.I once owned a cheap digital multi-meter apart from a small AVO meter. I never trusted the digital meter, but another would be handy at present. I did not get to the model shop today so I am at present looking at the 'oily alternative' you suggest. i am still torn between the ASP and the OS 10. There is just enough space on the Matador cowling to fit the 2 oz flexi tank I have with perhaps a small projection into the cockpit bulkhead. Also apart from more power the ASP is likely to have it will provide more weight to acheive the G/G position. The downside is that the flight times would be reduced. I was caught out last weekend yet again with my over powered Super 60. The Enya SS 40 in the plane drinks fuel as fast as Peter Barlow drinks alcohol in Coronation Street so I was faced with a dead stick landing yet again. It was no real problem as all my early planes landed downwind however there were a few expletives expressed on the flight line as they did not hear / see it coming-all captured on a video. MJE Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted March 16, 2012 Share Posted March 16, 2012 It's beginning to sound like I/C is a good way to go Mike, I'm sure it will be OK to poke the tank through the bulkhead a little. Quote Link to comment Share on other sites More sharing options...
Big Bandit Posted March 16, 2012 Share Posted March 16, 2012 Hi Mike, I'm with Chris and Martin on this one, it would be a shame not to get the old Matty flying again and if your already into IC and don't want to chop the front end about, go for it. On the other hand if your wanting to develop in the electric route, it's going to cost, but I must admit a vintage job sounds much better with a barking diesel up front, but a glow aint that far out. I like the OS 10 idea. It's all down to what your happy with. Cheers, Chris. Edited By Big Bandit on 16/03/2012 21:21:12 Quote Link to comment Share on other sites More sharing options...
Andy Gates Posted March 16, 2012 Share Posted March 16, 2012 Mike I have been following this discussion with great interest and like the others I am struggling to see how this all goes together. I have put your set up into a prediction program and it shows that a 8 cell 500mAH pack with your motor and gearbox on a generic prop of the size you stated should give a drop to 8.7v at full charge and full throttle. Current draw should be around 11.3A which is evidence that your meter is not reading correctly. Motor speed should be around 12000rpm and prop around 8000rpm producing about 11 oz of thrust. I hope this is of a little help to you. Quote Link to comment Share on other sites More sharing options...
Mike Etheridge 1 Posted March 16, 2012 Author Share Posted March 16, 2012 Chris and Chris, The only diesel apart from the ED Racer I have is an RC PAW 29 bought on E-bay from Dave Boddington. My nephew still has a few PAW 149's he used for 1/2 A combat, but he now lives in Wales. I could try both engines, the ASP 15 and the OS 10 by making two bearer plates. If the plane flies I could make a second fuselage to suit a brushless motor as I have the Matador plan and sufficient balsa. I could copy Lee Danns installation as he seems have re-designed the front end of the plane with plenty of thought? My original Junior 60 wings now serve three fuselages-Two Juniors and one Super 60! MJE Edited By Mike Etheridge 1 on 16/03/2012 21:44:58 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted March 16, 2012 Share Posted March 16, 2012 For what its worth Mike - my view is you should stick with the electrical route. There is nothing more annoying in this hobby than having to compromise an originally good idea. And I think your idea of electrifying the Matty was basically a great idea. Chris and Danny are very experienced on the old electric - as of course is Mr Ashby himself! And of course Steve to is well experienced electric modeller - though with definite recidivist IC tendancies if you ask me. If you guys together can't get this thing airborne (electric powered!) I'll eat my hat Go for it - realise your original vision! BEB Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted March 16, 2012 Share Posted March 16, 2012 But if Mike already has the I/C gear but would have to buy new electrics... Quote Link to comment Share on other sites More sharing options...
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