Goldberg Endurance Motor Replacement
01-19-2012, 12:25 AM
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Goldberg Endurance Motor Replacement
Love this old discontinued plane. What do you recommend for powerplant replacement based upon specs. I want better power, not wing-folding power!
Stock prop was a 12-8 folding. I don't want the gear drive any longer, just an outrunner on 3 cells.
Thanks.
Dan
Stock prop was a 12-8 folding. I don't want the gear drive any longer, just an outrunner on 3 cells.
Thanks.
Dan
Kit comes with a complete hardware package, including folding prop, spinner, 400 motor and 3.7:1 orbital gear drive. |  |
01-19-2012, 02:30 PM
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RE: Goldberg Endurance Motor Replacement
The nose of that little cutie just might be what decides your motor type.
It might be about the inner diameter right behind the spinner of an outrunner of the correct power for the weight, but not enough room for the motor wires.
I had a problem with that when replacing the multiplex motor/gearbox in a Spectra and settled for an inrunner and gearbox. Wouldn't suggest that for anything after experiencing it. In the meantime, I'll go look up a few things. brb
It might be about the inner diameter right behind the spinner of an outrunner of the correct power for the weight, but not enough room for the motor wires.
I had a problem with that when replacing the multiplex motor/gearbox in a Spectra and settled for an inrunner and gearbox. Wouldn't suggest that for anything after experiencing it. In the meantime, I'll go look up a few things. brb
01-19-2012, 02:43 PM
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RE: Goldberg Endurance Motor Replacement
One suggestion is to look for a brushless that is recommended as a 400 replacement. Notice the Goldberg specs call for a 400 motor.
A 400 outrunner at Tower is about $50 before their discounts. It's about 1.1" in diameter. It's advertised to put out about 155watt and they say it'll fly a heavier plane than yours. One thing you're not going to find is too many outrunners that fit that will want to spin your 12x8. The present gearbox makes that 8" pitch work.
Most of the outrunners that'd suit are going to want to spin a bit less diameter and significantly less pitch. And figure to need an ESC around 30A. The final decision on that will of course depend on the exact choice you make on the motor.
I put one of these http://www3.towerhobbies.com/cgi-bin...&I=LXLWU0&P=ML in a similar weight plane and have been very pleased. It would probably be much more than you need but sorta suggests what you probably could consider as more than enough.
So anyway, how much room do you have in that nose?
A 400 outrunner at Tower is about $50 before their discounts. It's about 1.1" in diameter. It's advertised to put out about 155watt and they say it'll fly a heavier plane than yours. One thing you're not going to find is too many outrunners that fit that will want to spin your 12x8. The present gearbox makes that 8" pitch work.
Most of the outrunners that'd suit are going to want to spin a bit less diameter and significantly less pitch. And figure to need an ESC around 30A. The final decision on that will of course depend on the exact choice you make on the motor.
I put one of these http://www3.towerhobbies.com/cgi-bin...&I=LXLWU0&P=ML in a similar weight plane and have been very pleased. It would probably be much more than you need but sorta suggests what you probably could consider as more than enough.
So anyway, how much room do you have in that nose?
01-20-2012, 10:03 AM
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RE: Goldberg Endurance Motor Replacement
The original brushed can 400 was only able to pull about 8 amps at 8.4 volts without destroying itself in short order. On racing models the guys pushed this to around 9 or maybe 10 amps and lived with the idea of burning the motors out within a hour or less of run time. Even at a self destructive 10 amps at 8.4 volts that's only a max of 84 watts of power. More realistically your sailplane ARF is running at around 65'ish watts.
The original at 635gms, or 21 oz, would be flying at around 47 watts per lb of airplane weight. So boosting this up to around 60 watts per lb will be child's play. And I'd assume that this old glider likely used Nicds or NiMh cells. Substituting the current Lipo pac for the old heavy pack will likely lose about 4 to 5 oz of weight. The motor weight would likely stay the same. So now we're down to around a 16 or 17 oz ready to fly weight which makes switching out the motor even easier.....provided you don't end up replacing the old motor with the new one and a big lump of lead to balance the model.
It is no trouble at all to find motors in the 28mm bell diameter range that will replace the 400. You're only looking for a motor that is rated at around 140 to 150 watts max and then you'll prop it to let it run at a nice easy 80 to 90 watts of power. But do try to select the lowest Kv value you can so the motor will turn as big a prop as possible. Then shop for props in the suggested size range for the motor that fold.
For example here's a motor which should fit and which will offer a good power boost over the old can and gear drive system.
http://www.rchotdeals.com/Products/r.../A2212-13.html
On a 3S pack and running at a fairly moderate 8 to 9 amps it'll deliver the 80 to 90 watts you want for a good but not overwhelming performance boost. And it'll be well under the max short burst limit of 12 amps. And with the Kv of 930 it should be good for use with a prop in the 9x5 to 10x5 range to let the motor remain fairly lightly loaded. From there you can tone it down with the throttle. But this much power shouldn't rip the wings off. A max power climb angle will likely be with the nose pointed up at 60 or so degrees and it'll get upstairs in a hurry.
That motor is just one example to demonstrate how the watts and Kv values work. By all means use this to pick a motor from your preferred brand if you don't like this one. If you do go ahead with buying this motor and the recomended ESC from then I can assure you that they are a great outfit to buy from.
The original at 635gms, or 21 oz, would be flying at around 47 watts per lb of airplane weight. So boosting this up to around 60 watts per lb will be child's play. And I'd assume that this old glider likely used Nicds or NiMh cells. Substituting the current Lipo pac for the old heavy pack will likely lose about 4 to 5 oz of weight. The motor weight would likely stay the same. So now we're down to around a 16 or 17 oz ready to fly weight which makes switching out the motor even easier.....provided you don't end up replacing the old motor with the new one and a big lump of lead to balance the model.
It is no trouble at all to find motors in the 28mm bell diameter range that will replace the 400. You're only looking for a motor that is rated at around 140 to 150 watts max and then you'll prop it to let it run at a nice easy 80 to 90 watts of power. But do try to select the lowest Kv value you can so the motor will turn as big a prop as possible. Then shop for props in the suggested size range for the motor that fold.
For example here's a motor which should fit and which will offer a good power boost over the old can and gear drive system.
http://www.rchotdeals.com/Products/r.../A2212-13.html
On a 3S pack and running at a fairly moderate 8 to 9 amps it'll deliver the 80 to 90 watts you want for a good but not overwhelming performance boost. And it'll be well under the max short burst limit of 12 amps. And with the Kv of 930 it should be good for use with a prop in the 9x5 to 10x5 range to let the motor remain fairly lightly loaded. From there you can tone it down with the throttle. But this much power shouldn't rip the wings off. A max power climb angle will likely be with the nose pointed up at 60 or so degrees and it'll get upstairs in a hurry.
That motor is just one example to demonstrate how the watts and Kv values work. By all means use this to pick a motor from your preferred brand if you don't like this one. If you do go ahead with buying this motor and the recomended ESC from then I can assure you that they are a great outfit to buy from.
01-25-2012, 10:40 PM
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RE: Goldberg Endurance Motor Replacement
Guys, thanks for the motor info. I did see that nothing other than an inrunner and gearbox would get me to the 12-8 prop and that what was getting me hung up. I want to go with an outrunner but as both of you have identified, prop size will be much smaller. I did convert the unit a while back to a like outrunner motor but was so dissatisfied with how it flew,I shelved it. What I found out was when underpower it wanted to climb like crazy (very pitch sensitive as well). I am sure itwas a combination or improper motor alignment and not enough nose weight (even though I added weight to get my CG.
Since both of you gave me a better understanding of an available (and acceptable) motor spec, I will go back to see what I did wrong and compare the motor I used to your specs. I believe I did drop down to a 10-7 or so based upon amp draw reported on a watt meter. Thanks for your research and feedback. I'll try to get it up in the air this weekend if weather permits.
Dan
Since both of you gave me a better understanding of an available (and acceptable) motor spec, I will go back to see what I did wrong and compare the motor I used to your specs. I believe I did drop down to a 10-7 or so based upon amp draw reported on a watt meter. Thanks for your research and feedback. I'll try to get it up in the air this weekend if weather permits.
Dan
01-26-2012, 01:13 PM
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RE: Goldberg Endurance Motor Replacement
Keep in mind too that most of the motors we've indicated WILL generate a far higher climb angle than the stock motor. Both because of the extra power and the lighter overall weight of the model.
Also the CG location suggested on the plans is generally a very stable one. But with such designs "stable" means that it'll want to raise the nose strongly with any rise in airspeed... such as you'd get with a strong motor on the nose. So the model may well have just been doing what science told it to do.
The way to get around this is to shift the balance point back about a 1/4 to 3/8 inch to the rear. You'll need to re-trim the elevator with a little down trim to restore a flat glide. But the model will have less desire to nose up with a rise in speed. On top of that adding a couple of degrees of downthrust to the new motor would not be out of place at all.
Start with a washer or two of downthrust under the motor's upper mounting tabs and shift the balance back about 1/4 inch. I think you'll find that it helps a lot. And depending on how many watts you're feeding it you may find that you want to use less than full throttle. Weigh the model and then calculate the watts / lb. If you've got a watt meter it'll tell you directly how much power full throttle is giving you. Divide that by the weight of the model in pounds. Anything over 80 watts/lb is going to be rather rocket like.
Also the CG location suggested on the plans is generally a very stable one. But with such designs "stable" means that it'll want to raise the nose strongly with any rise in airspeed... such as you'd get with a strong motor on the nose. So the model may well have just been doing what science told it to do.
The way to get around this is to shift the balance point back about a 1/4 to 3/8 inch to the rear. You'll need to re-trim the elevator with a little down trim to restore a flat glide. But the model will have less desire to nose up with a rise in speed. On top of that adding a couple of degrees of downthrust to the new motor would not be out of place at all.
Start with a washer or two of downthrust under the motor's upper mounting tabs and shift the balance back about 1/4 inch. I think you'll find that it helps a lot. And depending on how many watts you're feeding it you may find that you want to use less than full throttle. Weigh the model and then calculate the watts / lb. If you've got a watt meter it'll tell you directly how much power full throttle is giving you. Divide that by the weight of the model in pounds. Anything over 80 watts/lb is going to be rather rocket like.
01-28-2012, 08:34 AM
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RE: Goldberg Endurance Motor Replacement
Well, I had a bit of time to remove the motor and add the washers to the appropriate side of the mount. After cleaning the plane (man was that thing dusty!) I put the watt meter on the motor with a lipo 1000mah 3 cell. The motor is pulling 153 watts with a peak 16.3 amp draw. The prop is a folding 9x5. I might get to fly it today once I recheck the CG. The motor is a Hobby Lobby Atlas 2317-16.
Dan
Dan
02-03-2012, 08:48 PM
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RE: Goldberg Endurance Motor Replacement
Guys, thanks for your comments. The weather permitted a ton of great flights using a 1300 mah 3 cell 20c lipo provided pretty good performance. The Endurance flew even better with a 1000mah 3 cell 30c. Lighter battery and a bit more punch. I was throttling off and finding decent lift. The two red tail hawks over my place put me to shame however.
Nice!
Dan
Nice!
Dan
02-04-2012, 08:15 PM
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RE: Goldberg Endurance Motor Replacement
Nice to hear about your success Dan.
For my own intrest what was the final flying weight with the two different packs and what sort of climb angle and speed did you get with the 153 watts of power?
For my own intrest what was the final flying weight with the two different packs and what sort of climb angle and speed did you get with the 153 watts of power?
02-05-2012, 09:40 PM
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RE: Goldberg Endurance Motor Replacement
The weight with the different packs 22.5oz with the 1000 mah and 23.8oz with the 1300. I used 1 oz of lead in the nose for balance right behind the motor. Because of the servo tray I cannot move the battery up any further. I have the receiver pushed back into the fuse about the last 1/3 of the wing, then the battery about the front 1/2 of the wing. I ran a tach on the prop, the 9x5 was running 11,800 to 12,000 rpm max. It clearly is not a hot liner but a decent climb and of about 40-50 degrees as an estimate. I think I could experiment with prop size a bit.
