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Feb 28, 2005, 06:09 PM
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Hobbico Twinstar 25 twin engine Glow to Electric conversion. Suggestions please.


Hello, Tower Hobbies has just released (available late march) a 25 size Twinstar. I am thinking about converting this model to electric power. Have the following components on hand. 2- AXI 2808/24 motors, 2- Jeti 30 advance controllers, 1- TP 6000mah 3S3P 10-12C. The weight of the motors, ESC's, battery pack are almost the same as two 25 glow engines. Hobby Lobby quotes the AXI 2808/24 performance as follows: 10 cell 1700 mah, 9x5 prop, 19 amps, 157 watts. The plane should weigh 5-5.5 lbs. RTF. 314 watts at 5.5lbs = 57 watts per pound but the AXI's, 30 amp ESC's could be pushed a bit harder. What do you think? How will this setup perform? Thanks.
Last edited by jbj620; Feb 28, 2005 at 08:07 PM.
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Feb 28, 2005, 06:29 PM
gwh
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I saw one of these at my LHS this weekend. On paper I think you are going to be at the lower limit of the amount of power you would want. However twins often seem to get by with less power from two motors that you would expect from one motor of the combined power.

Since you have the motors I would go for it. The 2808 should work fine. According to HL on 10 cells these will turn a 9*5 at almost 11K RPM. That is pretty close to the performance of a bearing .25 motor.
Feb 28, 2005, 07:24 PM
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GWH, On paper it does seem underpowered. If you could prop to about 25 (30 max WOT) amps, put the ESC's in the engine nacell's and provide plenty of ESC cooling, IMHO this would improve performance. Other questions concerning this project: Keep wire length short between the ESC and motor..is this the right method? Could a "Y" harness be used on the throttle channel to control both ESC's or would this be a problem. Also, what happens to ESC BEC voltage when two ESC's are plugged into the reciever, double voltage or could one ESC BEC be disabled. Maybe both BEC's should be disabled and use a UBEC. Any suggestions?
Last edited by jbj620; Feb 28, 2005 at 11:13 PM.
Mar 01, 2005, 02:15 PM
gwh
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Here is one of several treads that discuss the wire length conundrum, https://www.rcgroups.com/forums/showthread.php?t=319700 It seems to come down to "it depends."

You can use a Y harness to hook up the ESCs. If your ESC's have the ability to choose between auto-calibrating the throttle stick and fixed end points, choose fixed.

If you were to hook up two BEC you would have double the current capability since they would be in parallel. Most people do not recommend using two at the same time.

You can disable one BEC by sliding the red (-) wire out of the RX connector on one ESC. However I think you will be much better off going to an UBEC and disabling both ESCs BEC.

If you have a computer radio you can mix the throttles on two separate channels. This will allow you to use a three position switch to choose left-both-right and do engine out maneuvers.
Last edited by gwh; Mar 07, 2005 at 08:53 PM.
Mar 01, 2005, 07:54 PM
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gwh, Thanks for your advice! Tower had a limited supply of Twinstar's in stock last night, got one on the way. I am concerned about the 2808/24 setup being underpowered. Would perfer using AXI's. Thought about trading for 2- 2814/12's but that may be overkill plus a weight gain of almost 4 oz. jbj
Mar 04, 2005, 12:34 PM
JB,
would you consider doing an article for us on your e-conversion? it'd be a nice addition to E Zone!
Mar 04, 2005, 02:09 PM
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The one thing that you must consider is your prop size, or rather clearance. The nacelles are pretty close to the fuselage. You probably couldn't use a prop larger than 10 inches in diameter which might not be enough to load the motor properly.
Mar 04, 2005, 05:11 PM
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Quote:
Originally Posted by AMCross
JB,
would you consider doing an article for us on your e-conversion? it'd be a nice addition to E Zone!
AMCross, Yes! That would be Great! jbj
Mar 10, 2005, 12:36 AM
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Quote:
Originally Posted by imodel
The one thing that you must consider is your prop size, or rather clearance. The nacelles are pretty close to the fuselage. You probably couldn't use a prop larger than 10 inches in diameter which might not be enough to load the motor properly.
imodel, Thanks for the reminder! jbj
Last edited by jbj620; Apr 05, 2005 at 05:29 PM.
Mar 11, 2005, 10:02 PM
I am also considering electrifying this plane. I have 2 Endo's and gearboxes, 2 - 50 A ESC's and 2 - 7cell GP 3300's not currently being used. Don't have any LiPos large enough. As I recall, there would be plenty of room for the Endo's and ESC's in the nacell's. Batts (2 packs?) could go in the fuse. Any comments on this set-up?

I flew this plane several years ago with Norvel .25's and it was fast and pretty manouverable. All in all, an enjoyable plane!

I would love to hear your flight report with your set-up.
Mar 11, 2005, 11:16 PM
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Originally Posted by gunfighter
I am also considering electrifying this plane. I have 2 Endo's and gearboxes, 2 - 50 A ESC's and 2 - 7cell GP 3300's not currently being used. Don't have any LiPos large enough. As I recall, there would be plenty of room for the Endo's and ESC's in the nacell's. Batts (2 packs?) could go in the fuse. Any comments on this set-up?

I flew this plane several years ago with Norvel .25's and it was fast and pretty manouverable. All in all, an enjoyable plane!

I would love to hear your flight report with your set-up.
Hello, The battery packs will fit in the Twinstar fuselage. I do not know anything about your motors / gearboxes. After a lot of research I had decided to run AXI 2814/12's instead of the 2808's but may end up with AXI 2820/10's just to make sure this model performs well. Having very limited experience with a model this size / weight has made the motor decision VERY tough. Thanks to the few that have replied. jbj
Last edited by jbj620; Mar 12, 2005 at 10:28 PM.
Mar 14, 2005, 08:32 PM
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Twinstar power system final decision


Finally decided on the Twinstar power system. 2- AXI 2820/10's, 2 Jeti 40 Advance controllers, TP 6000 3S3P. Hope to run APC 10x5e props. Found someone who had run motocalc numbers on this 2820/10 system (hope these are correct). Here are some wot performance figures. Amps 28.7 (57.4 ttl.), watts 231.6, rpm 9725, thrust 42.6. 463.2 ttl. watts at 5.5 lbs = 84 watts per pound or 81 watts per pound at 5.75 lbs. Maybe I went a bit overboard choosing the 2820. Returned the 2808's to the dealer today, not sure if he has 2820's in stock. Also, finally recieved a answer from HL today concerning proper AXI choice. L.A. suggested the 2814/12. I think this motor would have worked well. Was the 2820/10 a good choice? What do you think? I should be able to start the Twinstar build this weekend. Thanks! jbj
Last edited by jbj620; Mar 14, 2005 at 09:09 PM.
Mar 15, 2005, 11:05 AM
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gunfighter, I have been using the Endo's in some other conversions and was thinking about trying them in the TwinStar also. They will provide more than enough power. Please post your trial if you do it!
Mar 25, 2005, 09:01 AM
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Hello, Starting on the TwinStar today. I will take some photos and possibly submit a build thread in a couple of weeks. Thanks for your help! jbj
Mar 25, 2005, 10:10 AM
JBJ,
Hope you're still considering/planning to do it as an article for us in addition to, built off of, or in stead of doing a build thread.


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