Tom Wilson Posted January 15 Share Posted January 15 Can you please explain how you managed to get the 150 W power listed in the text from the 2409-18 bell motor, as the most that I can get is 61 W when using a 3S LiPo with an 8 x 6 prop. I even tried changing the motor for a 2409-18A outrunner but the maximum power was only 72 W. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 15 Share Posted January 15 17 minutes ago, Tom Wilson said: Can you please explain how you managed to get the 150 W power listed in the text from the 2409-18 bell motor, as the most that I can get is 61 W when using a 3S LiPo with an 8 x 6 prop. I even tried changing the motor for a 2409-18A outrunner but the maximum power was only 72 W. The motor in Tim's original article was a Tower Pro 2409-18 brushless outrunner, reportedly good for 180w on a 3s1p pack - like this one https://www.robotbirds.co.uk/65g-1000kv-tower-pro-2409-18-brushless-motor.html That's not a bell motor. Are you confusing it with the much less powerful bell motors, like the 2408-21 https://hobbyking.com/en_us/towerpro-brushless-outrunner-2408-21.html Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted January 16 Share Posted January 16 Never could get mine in the air very easily and when I did it flew like a pig. I think that the thrust line was at too shallow an angle because the nose dug in on take off. Still got the airframe kicking about somewhere if anyone wants a freebie spare. Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 16 Author Share Posted January 16 Since last night i have partly solved the problem. I happened to notice my Piwakawaka ( which I had forgotten about)on top of the wardrobe which had a similar type of bell motor. On checking , It was a 2408-21 as mentioned by Leccyflyer. with the watt meter in place it was reading over 200w initially and settled around 180W. As I said in my original post the Bm2409-18 is a bell motor. I swapped it over for the 2409-18A shown in leccyflyer's post. I then remembered seeing instructions for the HobbyKing ESC lying about and after consulting it I tried the Siebel again but this time setting the ESC as per the instructions and this time the power went up 107W, running at 10.5A. A vast improvement but still well below that quoted in the original build text. I will switch back to the original bell motor and try the slightly larger prop( a 9 x 4.7 which just clears the tail boom. Plan shows 4degs upthrust but I would call that downthrust as it is a pusher. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 Hi Tom - just from the figures you've posted for 107w at 10.5Amps, you battery voltage has dropped to just over 10v, whereas a fully charged 3s1p pack you would expect to be 12.6v, perhaps losing half a volt under load initially. That means either your battery is not fully charged, or it's not up to the current draw that the motor is asking of it. If the lipo was fully charged at 4.2v/cell so ~12.6v total pack voltage, and dropped half a volt under load, that would give you something more like the the 150w in the article. Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 16 Author Share Posted January 16 Battery is showing 11.4 v but 10.3 v under load. Now on charge and will post results later thanks. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 5 minutes ago, Tom Wilson said: Battery is showing 11.4 v but 10.3 v under load. Now on charge and will post results later thanks. Yep - that battery isn't far off flat. Let us know how you get on when it's fully charged. Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 16 Author Share Posted January 16 Now reading 12.7 off load, 1 cell a bit low at 4.15 v, others 4.30 v, and 4.28 v, total 12.7 V On Wattmeter 12.8 V showing off load. Now drawing 12.7 A and managed to reach 149 W. Have now put battery on different charger to try and balance cells. That middle cell doesn't want to come up. I have ordered some more silicon wire and when it arrives I will re-fit the original Bm2409-18 bell motor and see how that goes. The original problem was the ESC which I hadn't set by firing it up with the throttle fully open, and then the battery really need a charge. I have another new one but will need to change the plug on it, and that should give me the full 150 w. Model weighs in at 30oz which is surprisingly (for me) a couple of ounces below that quoted. As an ex Clyde shipbuilder I have always tended to build a little on the heavy side . Thanks for your help. 1 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted January 16 Share Posted January 16 Might be worth running the motor for a bit to draw that battery down some before you try another balance charge- it shouldn't really be going over 4.2v/cell, though the accuracy of the readings might not be perfect. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted January 16 Share Posted January 16 If you have access to a Battery Doctor then this would balance the cells much more accurately than the average charger. You are setting it to balance charge are you not? That 4.3V is rather worrying since an overvoltage is when they tend to blow up in flames. 1 Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted January 16 Share Posted January 16 Hi Tom, Good luck with the Siebel. As Martin has hinted, it's not an easy model to fly - probably due to that big flat nose, I think, causing airflow issues. I flew mine for quite a while, but I was happy to eventually retire it. Tim Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 18 Author Share Posted January 18 Hinted?........Yes, the high thrust line and the low drag line caused by that big flat front looks like it could be a problem. Maybe needs more than the 4deg. downthrust or trim in a bit of up elevator, but we will see how it goes when the weather improves. at least I have the power problem sorted now I think Tim that you said it might be helpful to move the u/c forward a little for take off on rougher strips.One of my chargers is a balance charger, and the other is not but gives the option to force charge on 1 cell setting. Whether or not it can select the low cell or not ,I don't know. I had a look on ebay and there seems to be quite a number of suitable battery doctors for around £16.00-£18.00 like the "Max B6" eg Can you recommend it ? Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted January 18 Share Posted January 18 When I said `Battery Doctor` I meant the one which has that trade name, about the size of a lipo checker. They discharge any high cells to the lowest voltage one, although it takes a long time and unless you keep an eye on it they will continue until all are flat-dead! Cheapo chargers like the B6 can be miles out when it comes to balancing; I know, I have two. I would say that the down thrust angle on the Siebel should be increased. Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 18 Author Share Posted January 18 OK, I respect that advice and I will avoid,Thanks. It is a difficult one with the thrust angle as the thrust line is so high above the CG point and centre of drag line, that increasing it could tip the model even further down, but so also would upthrust, so maybe up elevator would be a better option. I think only flight testing will find the best options. I'll have a further look for the battery Dr. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted January 19 Share Posted January 19 From what I remember of mine and from the results of testing I would say that the motor position as shown on the plan was pushing the nose down. I have a HK FPV powered glider which is similar and the thrust line is considerably up at the rear. Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 19 Author Share Posted January 19 Yes, this would make sense, particularly as with the big flat fronted nose giving a very high drag factor, it is inevitable that this is going to happen. Martin. Maybe that's why the Germans never adopted it. Fight testing should be fun then. New silicon wire arrived today and hopefully the heatshrink tomorrow and I will get the original bell motor refitted, but weather forecast is not good so there won't be any flying this week again. 1 Quote Link to comment Share on other sites More sharing options...
Christopher Wolfe Posted January 20 Share Posted January 20 I actually built this Free Flight version about 25 years ago Siebel Si 201 and it's still flying sweetly. Very stable with no vices. The only mods that I made were to add a thin steel thrust washer between the prop driver and the crankcase to prevent aluminium-aluminium galling and the wings were flat (no aerofoil) to make it eligible for the Free Flight 'Ebenezer' category. It won it's first comp (pilots choice) so as others have already remarked, get the thrust line correct. Fly it gently, it's a stable observation aircraft, not a fighter 🙃 * Chris * 1 Quote Link to comment Share on other sites More sharing options...
Tom Wilson Posted January 21 Author Share Posted January 21 Yes Chris, you have taken the words out of my mouth.. i think it should be flown sedately as it is for observation purposes. We know that drag increases with speed and speed needs more thrust to achieve, so the faster you go the more thrust force above the drag force is going to push the nose down. One thing however that has not been mentioned (well on your model it has) is the wing. On Tim Hooper's version it has quite a thick wing section and an increase in speed will cause more drag on the wing, which is much closer to the thrust line and higher than the main source of drag at the front canopy, so will partly cancel out the lower source of drag. So I think there will be an optimal speed for this model, which will only be found by flight testing but good to know that the free flight model flies OK without human intervention Quote Link to comment Share on other sites More sharing options...
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