Author Topic: Imitation conversion to electric (Read 10788 times)

Bill Ervin · « **on:** September 07, 2009, 09:01:36 AM »

Last spring my wife and I decided it might be a good time to move out of the Big City (Las Vegas, NV) and into the country (Henderson, NV). Little did we know that the process of buying a house would take 8 months! During that time my modeling "activities" consisted of hanging out on this forum and (sigh) looking at my mothballed planes.

I started an Imitation 4 or 5 years ago and got it to the "painted white" stage, while hauling my sofa, TV, refrigerator etc. I kept walking past it and wondered if it might not make a good conversion to electric. It was originally built for a piped VF40 but a firewall-mounted outrunner couldn't be that hard to retrofit, hmmmm...

This Labor Day weekend I finally got a chance to unbox all the stuff and take a good, hard look at my proposed project. Any and all advice is welcome as this will be my first attempt at an electric stunter. I'll add as much specific info as I can. Bill

Bill Ervin · « **Reply #1 on:** September 07, 2009, 09:14:45 AM »

Here's most of the pieces, the silkspan will have to be redone, I'll probably redo the open areas with polyspan and then finish it with a simple dope paint job. The motor I'll use is a Hacker A30-12XL for no other reason than I already have one. I'm also thinking of using a 5S A123 battery but I'm open to suggestions here too.

Bill Ervin · « **Reply #2 on:** September 07, 2009, 09:17:27 AM »

Even went so far as to carve out a pipe tunnel. I can fill it in with some wood.

Bill Ervin · « **Reply #3 on:** September 07, 2009, 09:24:49 AM »

The opening for the tank wasn't quite big enough for a 5S A123 flat pack so I'll have to modify the size and shape of the hole. I taped the fifth cell roughly in the spot where it will eventually go (fore and aft) just to get an idea of where the plane will balance.

Bill Ervin · « **Reply #4 on:** September 07, 2009, 09:34:55 AM »

Here are all the pieces taped onto the airframe. The flying surfaces are where they're supposed to be and the motor with prop is lashed onto the firewall. The darn thing balances right on the spar! I got real excited when that happened!

51 oz. all up as you see it in the picture, it still needs a speed control, timer, wiring and some kind of lightweight finish. Bill

Igor Burger · « **Reply #5 on:** September 07, 2009, 09:44:22 AM »

Bill, if I can recommend something - do not use those nickel connection plates on A123 cells, they have too high resistance, if I remembe well, it was 7mohm or so, it is too much ... remove them and use copper wires soldered directly on caps. You will need at least good 100W gun with large thermal capacity. And do all quickly.

Bill Ervin · « **Reply #6 on:** September 07, 2009, 10:18:51 AM »

I was not aware that, thank you Igor, will do that when making up the packs. It was your success with A123 cells that inspired me to use those also. In another thread you mentioned using 1 cell for each 10 oz. of overall airframe weight so I'm trying hard to adhere to that too.

Igor Burger · « **Reply #7 on:** September 07, 2009, 10:26:31 AM »

Question is, if you can find good prop for 5 cells, I think APCE 12x6 will be too large, so may be APCE 11x5.5 ... you will see ...

and what about CG?

however ... good luck

Alan Hahn · « **Reply #8 on:** September 07, 2009, 01:39:44 PM »

I see your Hacker A30-12XL has a kV of 700 rpm/Volt. I guess a 5sA123 battery has the voltage of a 4s lipo (??), maybe a little lower.

I fly my Vector40 with an APC 12-6 prop turning 8000rpm with a 4s lipo and a kV=746 rpm/Volt motor. You will need a higher rpm than me simply because your plane is a little heavier--maybe larger too (I am not familiar with the Imitation). Igor may be right that you don't have enough volts to turn that prop (12-6) at the rpm you need. Maybe the 12-8 prop will get you in the right rpm range.

I'd recommend the new Castle Creation Ice 50 amp "Lite" ESCr---because it also includes a data recorder, something pretty useful for setting up an electric system in flight. It even includes the pc hookup adapter in the price (they give you a coupon to redeem for the hookup adapter). With it you can record battery current, voltage, rpm, and the governor PWM output to the motor. Everything you need to dial in a system. Sorry for the advertisement, but I found my data recorder (an Eagletree) to be very helpful in figuring out what my power system was up to. Now it is basically included in the cost of the ESC.

Bill Ervin · « **Reply #9 on:** September 07, 2009, 02:40:55 PM »

Hi Alan, your input is much appreciated, I'll research the new CC ICE speed controls as I still need to buy one. Some of the online vendors for the A30-12XL show a Kv of 700 and some of them show a Kv of 770 (can't have too much confusion you know). The Kv that is laser etched onto the can of my motor is 770.

A common practice for the RC guys using A123 is to add one more cell to make it about equal in voltage to an equivalent Lipo. Based on my limited experience with these cells they will hold close to 3 volts under load until they hit the "knee" so a 5S1P pack has ~15 volts (and it weighs every bit of 13 oz.!).

The Imitation has a wing area of 630 sq. in. I'm going to try like heck to keep it in the low 50's. From what Igor writes maybe I should make provisions for a 6th cell too. Going to reread your post now because this is still kind of new to me.

Bill Ervin · « **Reply #10 on:** September 07, 2009, 02:53:29 PM »

Here is a link to one of several vendors. As far as I know this motor only comes in one wind. I was a bit confused already.

http://www.adchobbystore.com/hacker-a30-12XL.htm

Alan Hahn · « **Reply #11 on:** September 07, 2009, 04:43:13 PM »

Quote from: Bill Ervin on September 07, 2009, 02:53:29 PM

Here is a link to one of several vendors. As far as I know this motor only comes in one wind. I was a bit confused already.

http://www.adchobbystore.com/hacker-a30-12XL.htm

It looks like 770 is the official number and I'd go with that.

Did you check the top post in this forum? It has a list of setups, and I'd look for a plane that is about the size you have and see what they are using for rpm and prop. It helps to zero in on the parameters to adjust. Since you already have the motor and plane, the remaining parameters to find are the cell count and prop size. The prop size (diameter and pitch) are set by the thrust you need to fly the ~5.? s laps and the rpm your motor can turn under load with the cell count.

So for example, with five 3.0V cells (under load), your max unloaded rpm (kV*voltage) would be 11550 rpm. Since we shoot for 70-80% of that max value to allow the overhead needed for maneuvering, your target rpm would be 8100 to 9200 rpm. So I'm guessing that a 12-6 or 13x6.5 prop (APC TE the ones I'm familiar with) are reasonable starting points.

Another detail is to have enough energy (=number of cells) to finish the flight. With A123 you can't arbitrarily increase capacity without also changing the pack voltage, like you can with lipos. So if five aren't enough to fly a complete pattern, then you would need (perhaps) to add a sixth. That should still be ok with the ICE 50 since it is good up to a 6s lipo.

Igor Burger · « **Reply #12 on:** September 07, 2009, 11:38:59 PM »

You should better count with 2.8V pez cell. I have 9100 maximal rpm on axi 2826/13 with 690rpm/V (on end of flight).

A123 has small capacity, so the only way to fly it, is discharging to 95% of its capacity. I charge back 2100mAh and if I discharge it to 100% (switch off on low voltage) then I charge back 2200. So it is necessary to cout with voltage on end of flight. My Jeti Spin says that the minimal voltage during the flight (probably last climbing from 4L) is ~17V. So it will be ~14V for 5cells. So I really think it will need 11x5.5 and if pitch 5.5 is not enough, it can be still changed to 6 or so.

Bill Ervin · « **Reply #13 on:** September 08, 2009, 08:45:57 AM »

Okay, I'll plan for 6 cells. The airframe will handle the additional weight, and the motor and speed control can handle the additional voltage.

John Hammonds · « **Reply #14 on:** September 10, 2009, 08:26:29 AM »

Hi Bill,
I'm sure you already know this but when making A123 packs the "Button" end is -ve. It's the opposite to what you might be familiar with.

TTFN
John.

Bill Ervin · « **Reply #15 on:** September 10, 2009, 09:15:57 AM »

Thank you John, yes that is definitely one of those things I always try to remember and can never be reminded enough, like remembering to grab the handle right-side up. Those short-circuit spark "shows" always scare the heck out of me. bill

Bill Ervin · « **Reply #16 on:** September 12, 2009, 10:23:47 PM »

After reading through a few of the threads here I placed an order for a CC ICE 50 controller and Castlelink from Todd's Models. I ordered the heatsink version because it was only 12 grams more than the Lite version (it was 105 degrees here in Las Vegas on Sept. 12!) I'll feel a little better with the heatsink. Also sent Will Hubin an order for an FM-2a timer.

While waiting for the parts I decided to completely refinish the plane, the silkspan was ripped and poked in many places and every time I looked at it I discovered more hangar rash, spent the last week carefully removing all the silkspan off the open bays and carefully sanding off all the white dope with 400 sandpaper. It feels like I'm going backwards.

At this rate I should have a nice KIT of an Imitaton in a couple weeks or so (sheesh).

Crist Rigotti · « **Reply #17 on:** September 13, 2009, 05:34:25 AM »

Bill,
I'm sure when you are finished with refininshing it will look super. i've seen your previous work and you're no slouch. Keep it light!

Bill Ervin · « **Reply #18 on:** September 20, 2009, 01:05:13 AM »

Quote from: Crist Rigotti on September 13, 2009, 05:34:25 AM

Keep it light!

Thanks for the reminder Crist. Yes, controlling weight gain is foremost on my mind. The scale is never far away and gets put into service often.

Here I filled the pipe tunnel (actually more of a trough) with balsa scraps. You can also see where I prepped the edges of the open bays with fresh dope, tomorrow they'll get covered with polyspan.

Crist Rigotti · « **Reply #19 on:** September 20, 2009, 06:36:42 AM »

Man, that's looks good Bill.

Bill Ervin · « **Reply #20 on:** September 21, 2009, 05:37:51 PM »

Thanks Crist, I wanna get this thing just right for your visit to Vegas this winter!

The Northwest pilots most familiar with Ted's designs all agree that an airfoiled stab/elev should be combined with the thick, blunt wing section typical of Mr. Fancher's planes. My tail was simply a flat section with a round leading edge so I decide to block sand a more airfoiled shape into the horizontal stab. I discovered photographing a LE radius is more difficult than expected! Sanding the stab was much easier!

Crist Rigotti · « **Reply #21 on:** September 21, 2009, 08:33:21 PM »

Yup, I'll be there over the holidays! Get er done!

Bill Ervin · « **Reply #22 on:** September 26, 2009, 07:14:14 PM »

Recovered with Polyspan. First time using this stuff, couldn't find my Monokote iron so I used the heat gun. That was my first mistake , only burned three holes through the covering

, still think of it as a moral victory however. And in keeping with modeling tradition all the holes I burned were on the top surfaces. By the time I got to the tail feathers I had the Polyspan all figured out (i.e. I found my iron). It was nice outside today, the high temp was a mere 99 degrees, so I set her in the garden.

Sorry this isn't more electric C/L specific.

Bill Ervin · « **Reply #23 on:** October 04, 2009, 06:24:43 PM »

Doping, sanding, doping, sanding. Nothing really earth shattering here. Traditionally this is the point where me and the plane get kicked out of the house because of the smell. Ergo, pictures from the garage...

Bill Ervin · « **Reply #24 on:** October 09, 2009, 12:02:02 AM »

Figured something oughtta be done about that big, gaping hole through the nose. Originally for a 6 oz. plastic tank the plans show clips made of 1/16" music wire. For battery retention I thought that might not be such a good idea, guaranteed I'll find a way to short something out. Ended up filling the right side of the hole with a piece of 1/4" balsa, now I had a large cavity to stuff the pack into. The right side of the plane looks much better too!

More to come...

Bill Ervin · « **Reply #25 on:** October 09, 2009, 12:21:22 AM »

Purchased a small bag of No.4 socket head wood screws for mounting the motor and was about to drill holes into the firewall when my conscience told me to do it the proper way and make a new motor plate replacing the stock "X" mount. The problem was that I originally drilled and installed blind nuts for the Kraft Hayes engine mount for use with the O.S. 40 slimer. I needed the outside bolt pattern to match the KH mount, and the inside bolt pattern to match the back of my Hacker motor.

I am very happy with the results. Proof that, with enough cursing, almost anything can be fabricated with a hacksaw, hammer and files. Bill

Jason Greer · « **Reply #26 on:** October 09, 2009, 07:12:51 AM »

Nice work Bill! The motor should get plenty of cooling. Are you going to build a cowl to enclose it? I'm interested to see how the Hacker works out for you.

Jason

Dennis Adamisin · « **Reply #27 on:** October 09, 2009, 08:13:39 AM »

Bill - NICE work there!

I am with you about the battery pocket I like being able to slip it in from the i/b side and thus the battery straps do not have much to do.

BEAUTIFUL piece of work on the motor mount too. That WAS the right way to do it.

Can you share some info on the Hacker motor? Commutator & Magnet dimensions, KV, weight - or better still is there a website listing all this stuff? I am trying to put a table together on diffenerent motor dimensional data and ratings - Try to figure out how motors from different companies compare.

Crist Rigotti · « **Reply #28 on:** October 09, 2009, 08:31:57 AM »

Nice work dude!

John Witt · « **Reply #29 on:** October 09, 2009, 08:49:04 AM »

Good work, Bill. Lots of good stuff can be made with very basic tools and thought and care. We are spoiled by having a lot of ready-made stuff, but making the bits yourself is very rewarding. BTW, another name for a file is "Hand-held Milling Machine". That's a pretty installation, looking forward to seeing it in the air.

Is that a 50's Buick in the background?

John

Bill Ervin · « **Reply #30 on:** October 09, 2009, 09:19:01 AM »

Thanks fellas, Was up late last night working on the thing and I just got up. Jason, probably won't put a cowl on this plane because I'm already getting anxious to fly it! but it looks like it could be done without too much trouble. Dennis, here are some of the spec on the motor, it's designated as a A30-12xl. I HATE their designations because it doesn't make any sense to me, as far as I can tell the stator is 30mm in diameter and the length is about 26mm but I could be off on that, kV is 770, about 6.5oz

here's a link: http://www.adchobbystore.com/hacker-a30-12XL.htm

John, that's a 1950 Mercury Club Coupe, had it for 25 years, 2nd owner. It's all in one piece but I haven't given it any attention lately. Cigarette lighter and ash tray have never been used!

Crist, Gonna have this thing ready for you in Dec.!

Dang, now I gotta run to work...

Dean Pappas · « **Reply #31 on:** October 09, 2009, 09:41:03 AM »

Try Hacker-brushless.com
For those of you looking for motors for planes in the 60+ ounce neighborhood, the 40 sized Hacker outrunners and above have the third circumferential bearing a' la Plettenberg. Aside from the Shulman Fury (too big for us) they are the only ones I know of.

Mr Ranier Hacker also strongly suggests mounting the motor from the front and using a bearing support at the back of the bell for planes that maneuver violently.

Dean P.

Archie Adamisin · « **Reply #32 on:** October 09, 2009, 10:31:42 AM »

Bill,

You will be very happy with the Hacker. Rainer makes great motors. I used his FAI B40 in-runners in F5D and they were insane as they were full of copper and very low resistance. My dad and brother have used their small out-runner motors in indoor R/C models and they were fantastic.

This motor is the one I would use if I were using a Hacker. Great Choice!!

Archie Adamisin
Muncie, Indiana

Igor Burger · « **Reply #33 on:** October 09, 2009, 11:06:53 AM »

Quote from: Archie Adamisin on October 09, 2009, 10:31:42 AM

very low resistance

Anyone knows exact number? ... and no load current? I hate those pages showing lot of words and no numbers

Bill Ervin · « **Reply #34 on:** October 09, 2009, 11:33:41 AM »

Thanks for the vote of confidence Archie, support from a fellow pylon racer is always welcome! The most popular application for this motor is in an RC 3D plane called, apropriately, E3D with 4 cell lipoly and a 14-7 apc. In that plane the motor is mounted from the front and is unsupported. I'll likely be using a prop 11-12 inches in diameter so GP forces shouldn't be quite as bad (even less if using a wooden Xoar) but will heed the warning suggested by Dean and Mr. Hacker. Bottom line this will be an experiment. Worst case a motor swap should be easy! Bill

Igor Burger · « **Reply #35 on:** October 09, 2009, 11:41:17 AM »

http://www.espritmodel.com/index.asp?PageAction=VIEWPROD&ProdID=4990

Bill Ervin · « **Reply #36 on:** October 09, 2009, 11:44:35 AM »

Igor, Ri appears to be .034 ohm

Thanks for the link Dean, according to their site the kV for this motor appears to be 700 yet the laser etching on the endbell of mine clearly shows 770. I suppose I could test for the actual kV.

Igor Burger · « **Reply #37 on:** October 09, 2009, 01:43:03 PM »

Yes Bill, thanx, I found data already ... on link in post over.

Crist Rigotti · « **Reply #38 on:** October 13, 2009, 09:33:36 PM »

Quote from: Dean Pappas on October 09, 2009, 09:41:03 AM

Try Hacker-brushless.com
For those of you looking for motors for planes in the 60+ ounce neighborhood, the 40 sized Hacker outrunners and above have the third circumferential bearing a' la Plettenberg. Aside from the Shulman Fury (too big for us) they are the only ones I know of.

Mr Ranier Hacker also strongly suggests mounting the motor from the front and using a bearing support at the back of the bell for planes that maneuver violently.

Dean P.

Please elaborate on this 3rd bearing. Where is it located? Got any pictures of a Hacker taken apart that shows this bearing? any websites that show the "guts"? Thanks.

Alan Hahn · « **Reply #39 on:** October 14, 2009, 08:18:35 AM »

Crist,

I think the Scorpion 3032's have this ring bearing to support the long iron shell length---at least they do now after some people had flexing issues and had the shell/magnets contact the stator head.

I am wondering if the two end support like you have on your current plane more or less takes care of the problem.

Dean Pappas · « **Reply #40 on:** October 14, 2009, 12:24:22 PM »

Hi Crist,
No I don't have any pictures and Alan described it well: it supports the open end of the bell.
It's kind of a no-brainer when you think about it.
The second external support was described in pictures that several of us posted. I'll go look for the old thread with the pictures and post the link.
later,
Dean

Crist Rigotti · « **Reply #41 on:** October 14, 2009, 01:13:23 PM »

Thanks Dean. Then this bearing is the size of the internal opening of the bell. I see that the Hacker 40 series is 9.3 ounces. That must be one big bearing! Still I'd like to know more about the Hacker series motors.

Igor Burger · « **Reply #42 on:** October 14, 2009, 02:54:02 PM »

such a long bell has very low self resonantion frequency. Lower than expected rpm, so it needs support on both sides.

For example AXI 2816 has resonantion at ~12000 rpm. We wanted extend the length of the motor for higher power, but they told us that it is danger and the only way is to extend the diameter.

Dennis Adamisin · « **Reply #43 on:** October 14, 2009, 03:00:11 PM »

Quote from: Igor Burger on October 14, 2009, 02:54:02 PM

such a long bell has very low self resonantion frequency. Lower than expected rpm, so it needs support on both sides.

For example AXI 2816 has resonantion at ~12000 rpm. We wanted extend the length of the motor for higher power, but they told us that it is danger and the only way is to extend the diameter.

But wait! AXI makes a 2826, many of our big airplane flyers are using them and are VERY enthsiastic about them. Presumably the longer moter would have a lower resonance RPM..?

Igor Burger · « **Reply #44 on:** October 14, 2009, 03:10:04 PM »

I know ... I fly them too, but at 9000rpm.

Longer motor will go from 12000 to 9000 and it can resonate. Therefore they do not want to make it.

Alan Hahn · « **Reply #45 on:** October 14, 2009, 03:21:12 PM »

Quote from: Igor Burger on October 14, 2009, 02:54:02 PM

such a long bell has very low self resonantion frequency. Lower than expected rpm, so it needs support on both sides.

For example AXI 2816 has resonantion at ~12000 rpm. We wanted extend the length of the motor for higher power, but they told us that it is danger and the only way is to extend the diameter.

Maybe that 2816 is a typo --AXI makes a 2814, not a 2816. So I think Igor means 2826.

Igor Burger · « **Reply #46 on:** October 14, 2009, 03:23:21 PM »

soooooryyyyyyyy

yes, I mean 2826

Dean Pappas · « **Reply #47 on:** October 14, 2009, 08:57:53 PM »

Quote from: Igor Burger on October 14, 2009, 02:54:02 PM

such a long bell has very low self resonantion frequency. Lower than expected rpm, so it needs support on both sides.

For example AXI 2816 has resonantion at ~12000 rpm. We wanted extend the length of the motor for higher power, but they told us that it is danger and the only way is to extend the diameter.

Now that is interesting information, Igor! Thanks.
So our friends at AXI are working on the special problems posed by Stunt?
Regards,
Dean

Larry Wong · « **Reply #48 on:** October 14, 2009, 10:34:47 PM »

Yep that's what happen to my 2826/10 AXI when I tryed to use the new 13x4.5 EP props , when I lower the RPM and use my old stand by 12x6 EP every thing was quiet again.

Mike Scholtes · « **Reply #49 on:** October 14, 2009, 11:07:14 PM »

Larry, what rpm did you find to be a problem with the 2826? And what was the nature of the problem? Are we saying the motor flexes if supported only at one end, at least at a certain rpm with a certain prop?

The new Stunt News shows a Bob Hunt (IIRC) project with a mount that supports the motor at both ends. That should solve the problem and looks like a good idea for all the higher power motors swinging big props. To our combined knowledge, is anyone selling or getting ready to sell commercially mounts of this kind? Seems like the electric RC pylon guys would have this figured out as their models take huge G loads and run at high rpm.

Author Topic: Imitation conversion to electric (Read 10788 times)

Alan Hahn

Alan Hahn

Alan Hahn

Alan Hahn