jschenck

My Feedback: (23)

My brother-inlaw bought the RTF Aspire last october and we have been struggling with it since. It is underpowered and goes through the batteries like crazy. The included 1500ma battery wont even fly a full minute with a full charge. The plane climbs at a very lazy rate.
One other club member had the same experience with his Aspire RTF and spent big money on a speed-600 + gear reduction + 8 cell batteries. wow, does that perform well.

but that costs a lot of $$$'s

So I've convinced the brother-inlaw to stick the Magnum-10 glow engine on the nose of his aspire and some basic aluminum landing gear. My thought is the airplane will be lighter, better climb performance and cheaper to fly (those $10 props get eaten on every hard landing, much more expensive than the glow fuel)

Has anyone done a similar conversion? any advice? I plan on mounting the engine so the muffler is pointing straight down and adding tubing on the end of the muffler to direct as much of the oil off the plane as possible.

RCSM

My Feedback: (1)

my brother tried a 09 on the greatplanes spirit it was a good flying plane with that moter.we tried it with a highstart first but the flyingfield we fly at does not have the room needed .also another good moter is the norvell 074 R/C it puts out as much power is a ten but its weight is about 2.6 OZ.you will have to put a plywood firewall to mount the moter.If you want to save weight and need to buy a moter I would go for a norvell.

Alvin Souphound

Jschenck:
IMHO your battery pack is below minimum of 1700 mAh. With an 8 cell 2400 mAh pack the stock motor will climb out at full throttle and cruise at 1/2 throttle provided you have an ESC. I read this info in a MAG article while I was researching information for a project I'm working on. It also said the run time (depending) on the throttling can be as long as fifteen minutes.
Hope this helps,

jschenck

My Feedback: (23)

The battery that came with the RTF version is a 6 cell 1500MA pack that doesn't even get it across our flying field with a full charge. The ESC that comes with it seems to handle the 7 cell pack fine, but still not much more than 30-45 seconds at full throttle.
The only acceptable pack is the 2400MA 6 cell he got which gives ~3 minutes at full throttle. But this is with a fairly shallow climb rate.

My thought is it will cost too much to make this airplane perform well. It'll require at least a gear reduction, new prop system and a number of 7-8 cell NMH packs of 2.5-3.3 amps size. a speed 600 may even be required as the 550 seems to be weak.

I think the sail plane is better suited with the lighter combination of a small glow engine and some landing gear!

I do like the Norvel idea, but I already have the Magnum GP-10 which seems to run good. I think I'll try a 7x4 prop first and see what I get out of that.

Alvin Souphound

I am running a 550 on a HAN9510 6 cell 1500 mAh Battery, WITHOUT an ESC,and mine runs 5 1/2 minutes full throttle. If you can get no more than a couple of minutes out of a 2400, it sounds like you have some mighty high resistance somewhere. Have you put an ampmeter in the circuit to see what kind of current it's drawing?

Alvin Souphound

Adding the glo engine and landing gear to the Aspire will effectively convert it to something similar to a "Butterfly" which fly great

jschenck

My Feedback: (23)

It is possible that there is a problem with the ESC - it seems to cut the motor off before any perceptiable drop in RPM.

Perhaps I'll look into what a direct drive conversion (no ESC/BEC) would take.

Thanks for the hint, Alvin!

Alvin Souphound

jschenck:

If I understand the BEC circuit correctly, the motor shuts down before battery voltage drops from 7.2 volts (6 cell) to 4.8V in order to have the reserve power needed for the RCVR. The ESC may be the culprit, but I would start with the easy part 1st. You say the battery is fully charged. How do you know, have you tested it under load? To test the batteries correctly you should use an expanded scale meter which has a built in load of 275 mA
and with the load, determines the condition of the battery. Charging overnight, or checking with a common VOM will not assure the battery is fully charged.

jschenck

My Feedback: (23)

I'm not sure the best way to test the batteries. We have 4 pack now, a 1500x6 an 1800x7 a 2400x6 and an old 1500x6. All are nicad.

I consider a battery fully charged when it spikes in temp. This may not be too nice to the battery, but it is probably a full charge at that point. Our test has been to put it in the Aspire and fly them until the ESC cuts out. The 1500x6 that came with the airplane will run about 1 minute with the advertised 20 degree climb. not too much altitude there. the 2400 will get about 4-5 one minute runs. The charge lasts longer if we don't run it constantly presumably since the battery and motor don't overheat as much.

I do have a nice voltmeter, the Sears equivalent to a Fluke. I have not thought to measure voltage right after a flight, perhaps I'll try that before hacking up the aspire for the GP-10. I don't believe this meter can put a load on the battery though.

Alvin Souphound

Jschenck:
I believe batteries can be eliminated as the problem since low runtime occurs with multiple battery packs. In the absence of test equip. ie. power supply, expanded scale meter etc. You can check the battery voltage before and after the motor run with the meter you have, the voltage should be above 6 Volts after run/shutdown. (Six volts is considered 'discharged' on the 7.2V pack.) If you do a bench check run, you will get some idea of the ESC/BEC shut-off voltage setting after the motor stops. You will also be able to check the temperature of the motor. I'm looking for a diagram of an ESC/BEC to see if I can find the value of the voltage regulator.
1/12/03 UPDATE: I found a diagram, and it uses a 5V regulator which is tied to a PNP transistor. For PNP transistors, the emitter needs to be 0.7V positive (5.7V) with respect to the base, for current to flow. Bottomline....6V is a good number.

lhatton

My Feedback: (1)

My Aspire was a dismall climber also.

A 6 cell 1700 would let it cruise around the field looking for a bump to climb in. A 7 cell would climb, but still very disapointing.

My solution was a Master Airscrew Motor/Gearbox/Prop combo. 3:1 ratio with I think a 12 or 14 inch folding prop. Takes some tweaking to get it in and still use the canopy in the stock position.


RESULT....WOW!!! I get 2.5 strong climbs to 500 or so feet on the 6 cell and the 7 gives 2 VERY STONG climbs. Enough that you think it will stall, but still has quite a bit of elevator travel before it does.

It does thermal well onece you get it going.

Price 35.00 at my local shop and about 2 hours refitting.

Made the Aspire what it should have been from the start.

Les

jschenck

My Feedback: (23)

I may have to suggest that to my brother in-law. We have not converted it yet due to lack of time and I've been repairing another airplane. I know he really wanted the electric to work as there are many advantages.

I'll throw this by him and see what he has to say.