Planning e-conversion for 33% extra

[jbm]

Got ya on the ESC

I'm still back and forth in my mind between the Hacker and a cheaper setup... I guess I need to just grow a pair and get on with it LOL.

I'll keep you all posted.

[Mike Anderson]

Here's some motor calc's to get you thinking about this a bit more. I selected these motors using these criteria:

• Keep prop speed below 6500 for low noise (cell count)
• Static current selected so that peak efficiency current is at 1/3 throttle
• Pack capacity selected for duration = ~10 minutes at 2/3 throttle
• Only consider 10 to 12 S packs

It's hard to beat the A60 18L on 12S . . .

[jbm]

Hey Mike,

Thanks for posting that dude Glad I'm not the only one who makes spreadsheets of this kind of stuff lol!

Your prop sizes are smaller than I was expecting; maybe I'm thinking wrong on that front... I assume you went with the A60 18L setup for the Suk then? How does the real world compare to the calculations? CG might be harder to attain with such a light motor I guess.

I'm also surprised how well the cheap HXT motor does on your calculations. Has anyone had experience with the EMP branded motor that looks to be very similar to it?

[whidbey1]

We were talking bout electrics at the field yesterday, people said this place has good deals and customer service is outstanding.
http://www.rchotdeals.com/

Good Luck

Bill

[Kiwi]

JBM,

I have the HXT 80-85 setup going into a 30% Pilot RC extra. Its taking longer than I planned due to some eccentric qualities I have about doing things different but here is a brief explanation.

The motor I have tested and it works fine. I am using a 100 amp Turnigy ESC from Hobby City. Appears to be OK in the static tests. But the motor has a design error and that is what causes the bearings to fail.

If you have access to someone with a lathe all you need to do is make a thin walled sleeve 35mm long that goes between the two bearings. That way when you yank on the prop nut you not crush the bearing races. They are made for rotating loads, not side thrust thus the failure issue.

I purchased bearings from VXB with ceramic balls. These and the bearing spacer will make this motor last a life time.

The ESC I feel is a tad on the light side and I would like to have something with a bit more reserve. 120 to 150 amp would be ideal.

Prop I have chosen is a 24 x 12 E. But I purchased one of everything from 15 inches up last week to have props to play with. Again Hobby City products.

Battery packs I will go with 12S x 8000 Zippy as it looks like I can get two rounds of sportman in with that setup and still make it home.

I also purchased an Emcotec in line switch but you can do the same with either a powerpole switch or a Deans plug jumper switch as well.

I should have everything here at the end of next week so it would be good to compare notes as you go.

[Mike Anderson]

	Quote: Originally Posted by jbm
	Your prop sizes are smaller than I was expecting; maybe I'm thinking wrong on that front... I assume you went with the A60 18L setup for the Suk then? How does the real world compare to the calculations? CG might be harder to attain with such a light motor I guess. I'm also surprised how well the cheap HXT motor does on your calculations. Has anyone had experience with the EMP branded motor that looks to be very similar to it?

Just a couple of clarifications.

1. I have not personally built or flown any large 10 or 12 cell planes yet.
2. Those calcs are my own from 1st principles based on published motor constants
3. I assume a Prop power factor mor in line with a typical Mejzlik in that size range.
4. The prop is sized to absorb the calculated full throttle static power, which will never be acheived in flight, so a one inch larger prop would probably be just fine in actual in-flight at partial throttle settings. (Hmmm, just got an idea for another modification to my XLS....)

Side note: My gas-engined H9 Yak 54 is giving me so much grief right now, I'm starting to seriously think about electrifying it. (The airframe actually shook apart last week!) But I would have to buy a gas engined generator to make it all work. . . . .

[jbm]

Appreciate that Mike thank you

Kiwi, having a good friend who owns a machine shop I'm not averse at all to some modification like you suggest. On that subject, I wonder if I could avoid a number of issues with the HXT / EMP motor by using it in the traditional outrunner 'back to front' configuration. I could have my friend turn up a prop adapter for the plain end of the shaft, perhaps even with a typical 4 or 6 bolt gas configuration if he's feeling generous. That way the torque to pinch up the prop is not affecting the bearings, and the pull of the prop in use is not trying to separate the two parts of the motor. What do you think? Obviously I'd need then to mount the motor in a cage type mount, but that kind of fabrication is no sweat at all.

[Kiwi]

John,

I just had a look at your profile and had to pick myself up off the floor from the laughing. Looks like many of us have been down the same lane mate.

Anyway the HXT motor. If you reverse it then you get away from all the issues but at the same time if you fit the spacer (very simple to make) you get the same result and the ease of installation without adding weight.

Now I have made a new shaft for mine and all the shaft will do is hold the motor together. The prop will be mounted AKA DA 50 with the same bolt hole spacing etc. The shaft will also be much smaller as at present it is 12mm and that is a hole in the prop that means your stuffed if you want to use it someplace else. I think the DA50 hub is 10mm or 3/8. The intention is to have that protruding shaft plain. The nut to hold the motor together will likely be 10mm as well and that will be buried in the prop hub. I am sure you get the idea. The end of the new shaft will be drilled and tapped for a spinner bolt if I ever need one.

I have the first part of the shaft ready today so may put up a photo to explain more clearly what my intention is.

There have been reports of magnets popping out on the HXT as well but mine are fully bonded and the glue has formed a good bead all the way round each magnet. I also used an iron bar to stick onto each magnet and try to lift them off the shell. None of them moved at all.

The bearing numbers if your interested are 6801RS and 6901RS. Easy to buy good quality at the local bearing supply shop.

People that have written to me about the HXT say that an E prop is absolutely critical. The props for gas motors dont work, its that simple to say.

[MarkF]

LBM, I think you should look at a Neu 1527 1.5Y 6.7 gearbox. This setup will give you the power your looking for and will run on 12s 1P castle 110 controller and apc 27 x 13 or 26 x 15 electric prop. This has been used on many 33 % planes with great success.

Mark

[Kiwi]

OK

Here is the super simple fix to the bearing problems with the large Turnigy outrunners.

This sleeve is aluminium and .05mm longer than the bore in the field winding casing. What this does is space the bearings apart so when you wrench on that prop nut you have a solid shaft from the rear circlip to the nut.

This way the bearings take no crushing loads from the nut torque.

[jbm]

Awesome help, thanks Kiwi I'm always willing to give budget components a go- as long as you've got your eyes open and are careful its ok, and it has panned out well for me in the past. ( In fact my first lovely DA-85 died the prop hub death not long after I bought it... any piece of gear can fail- the difference being that with a premium product you send it in for service, whereas with something lesser you've just got to expect to deal with it yourself )

[Kiwi]

Very true mate.

I have another thread going here that I will put a link to as I have also made a new shaft for this motor that ups the anti even further I think.

Building a budget sized 50cc Electric