Mode1Mike

Hi guys,

I have a GP Spectra, that is all stock. I'm looking to upgrade to a brushless motor and speed control...can anyone suggest a drop-in replacement?

Not looking to turn it into a rocket ship....a 30 to 50% increase in power though would be handy. I'd also like to continue using the 6 cell NIMH batteries with it. Is this doable with a brushless setup?

Thanks for any guidance.

Mike

rscarawa

I use an Axi 2814/12 on 2s lipo with a 10*7 prop. It is not balistic but it gets me about 300-400 feet up in 30 seconds. It would be more impressive with 3s. You 6 cell should be ok. You will need a 30 amp controller for this setup.

BMatthews

The advantage you would gain in weight by going to Lipo would be worth it. The climb would improve thanks to a lower weight and the glide would be better thanks to the lower wing loading. And both Lipo packs and the Lipo chargers are super cheap now thanks to being able to buy stuff online. You sure you can't spring for the extra cost right away?

For a budget motor something like these two suggestions from Hobby King would be suitable;

http://www.hobbycity.com/hobbyking/s...trunner_1050Kv

This would be a nice motor as well but you'd need to run it with a 12 to 14 inch folder on the 6 cell Nimh pack to make it draw enough current.
http://www.hobbycity.com/hobbyking/s...utrunner_Motor

This one looks like a nice match for your 6 cell packs. Run it on about a 10 to 12 inch prop with a 5 to 6 inch pitch and it should pull the freight in the way you want.
http://www.hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=3883&Product_Name=TR_35-30C_1100kv_Brushless_Outrunner_(Eq_AXi_2808)

Ideally with any of these you would test it with an inline wattmeter to make sure you prop it within the motor's power handling capacity. But if you don't want to pay for a meter then a good way to avoid over proping but still get the power out of the motor is to ground run the motor for 30 seconds at full power with the prop being tested. Shut it down, wait for 30 to 40 seconds for the heat to conduct through to the outer bell and touch the motor. If it's too hot to hold onto without pain then your prop is too big and pulling too many amps. You either need to go to a lower pitch or arrange for more cooing air to flow through the motor. If it seems OK repeat the test but this time run it for a solid minute of ground time. Again, wait for 30-40 seconds for the heat to soak to the outside and touch the motor bell. Again it should not be so hot that you cannot hold onto it without pain. Start with smaller diameter and pitch props and work your way up to where the motor is just tolerably warm from the test running. That should give you the power you need and still ensure a long motor life.

rscarawa

I would only comment on one thing about the 2808 motor. From my experiance, the Spirit/Spectra tends to require nose weight to bring it to the rearward most CG point. If that is true on your side, consider a slightly bulkier motor since it is way a the front of the plane. Before you order, figure out how much weight you need up front and see if the 2808 will do it. If you need to add lead, why not add more motor? If not, the 2808 will be good enough to get you up there.


Scot

BMatthews

An excellent point. A bigger and heavier motor with the same Kv value will turn the prop at the same power level but be heavier doing it. And the side benifit is that the maximum wattage is higher so it won't get as warm.

If it balances now you may as well buy a motor that mimics the old motor and gear box for weight since it'll be needed anyway.

Mode1Mike

Thanks for the advice guys....I will give those items a look!

rscarawa

I have a question for Mode1Mike. Is the Spectra fuselage larger than the Spirits? I am looking to rearrange some things in my Spirit and wonder if I would get more room with a Spectra. I currently have to remove the wing to get at the battery. Does the Spectra have a battery door?


Thx


Scot

da Rock

I'm slapping a Spectra together right now and it's got a fair amount of room in the fuselage. The width is just under 2" and the area under the wing is about 3" deep. Forward the wing, the area under the canopy is basically a little under 2" by a little under 2". The canopy can serve as access.

The Spectra actually does not have a real beefy strutcture. I think they copied a Gentle Lady and only had the dimensions and drew up something that suited the "gentle" name.

BMatthews

There's a parallel thread running at the moment about a guy converting an Electra to brushless. It may be of intrest to anyone looking at this thread since the models are not that unsimilar.

http://www.rcuniverse.com/forum/m_9925702/tm.htm