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Author Topic: Change from gas to electric  (Read 2266 times)

Offline tedlee

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Change from gas to electric
« on: May 01, 2010, 08:03:15 PM »
I have a 31" span CL Stinson Reliant plan from a 1947 Mechanix Illustrated.What would be involved in changing from gas to elec.? Thanks, Ted.
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Offline Dennis Adamisin

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Re: Change from gas to electric
« Reply #1 on: May 02, 2010, 10:20:55 AM »
tedlee

I see this your first post - WELCOME to Stunt Hanger & the electric forum.

* 31" span makes it sound like one of the smaller systems would do the deed - probably a 2210 class motor, 3Sx1100 (or so) lipo and a 18A ESC depending on what yuy have in mind.  Is this intened to be a scale model with a throttle?  If single speed then you will need a timer.

* If you want the full function of the throttle then one of Wil Hubins's or Clancy Arnold (U-Tronics) single channel systems should do the deed.  Hope some of the electric Scale or Carrier fliers can weigh in on this subject!

* Do you know what the original weighed with an IC engine?  I am hoping it is under 14 oz or so!  What power?

* For comparison's sake, go to the "List your Set-up's" thread at the top of the Electric forum and read through,  I have a/12A Pathfinder that is set up for full CLPA pattern, uses a 2210 motor a 7x5 prop and a 3Sx1300 pack using a 18A ESC and a Hubin timer.  I would think the flight profile on your Stinson would not include the whole pattern so you might be able to downsize & lighten your battery a little....

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Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Tim Wescott

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Re: Change from gas to electric
« Reply #2 on: May 02, 2010, 03:56:55 PM »
Quote from: Dennis Adamisin on May 02, 2010, 10:20:55 AM
* If you want the full function of the throttle then one of Wil Hubins's or Clancy Arnold (U-Tronics) single channel systems should do the deed.  Hope some of the electric Scale or Carrier fliers can weigh in on this subject!
Does anyone make a three-line adaptor for electric throttle?

Yes, it's strange as all get-out, but it's still kewl sounding idea.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Tim Wescott

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Re: Change from gas to electric
« Reply #3 on: May 02, 2010, 04:00:17 PM »
Ted:

Note that getting the battery and motor physically mounted is left as an exercise to the reader.  If you're lucky you'll just have to move the firewall forward; if you're not lucky you'll have beam mounts that are a structural part of the fuse that you'll have to reengineer, or that you'll have to mount the motor to (and those motors want to be bulkhead mounted).

Have you flown electric before?  Do you know all about airflow over the battery and motor, and mounting the batteries so you can take them out for charging?
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline tedlee

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Re: Change from gas to electric
« Reply #4 on: May 02, 2010, 07:36:59 PM »
No wt. was given on the 1947 plan for the Stinson Reliant model.I would probably use a single speed throttle, The original model used a Ohlsson "23" rotary valve engine. Thanks Ted.
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Offline john vlna

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Re: Change from gas to electric
« Reply #5 on: May 13, 2010, 12:59:15 PM »
I am fairly new to electrics. What is a 2210 class motor?
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Offline Mike Anderson

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Re: Change from gas to electric
« Reply #6 on: May 13, 2010, 01:35:44 PM »
Quote from: Tim Wescott on May 02, 2010, 03:56:55 PM
Does anyone make a three-line adaptor for electric throttle?

Yes, it's strange as all get-out, but it's still kewl sounding idea.

We fly electric carrier with 3-line systems driving a pot (rather than a throttle arm), which controls a Clancy U-tronics system.

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Mike@   AMA 10086
Central Iowa

Offline Mike Anderson

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Re: Change from gas to electric
« Reply #7 on: May 13, 2010, 01:44:23 PM »
Quote from: john vlna on May 13, 2010, 12:59:15 PM
I am fairly new to electrics. What is a 2210 class motor?

John - a 2210 size motor is very small.  A very broad-stroked explanation is that the '22' part is the diameter and the '10' part is the length (in millimeters), but some mfrs. measure the outside dimensions and some measure the stator (windings) when assigning those numbers, so one person's 22 is another persons 28 or so.  As another example, an Axi 2826 and a Turnigy 3548 are roughly the same size and weight.

In this instance, I think that Dennis is refering to a motor that is in the 1/2A power range, since the model that was inquired about is only 31" span.  However, after seeing that the original was powered with a .23, I think something in the 300 Watt range ( A Turnigy 3536 with a 3-cell battery) would turn about a 9" prop at about the same RPM as the .23 glow.

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Mike@   AMA 10086
Central Iowa

Offline john vlna

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Re: Change from gas to electric
« Reply #8 on: May 13, 2010, 09:44:50 PM »
Mike, thanks I understand the terminology now. FYI I recently converted an old 1/2A all sheet Fokker D-7 to electric. I used a Turnigy 2211-2300, It is about 24mm x 24mm. Good motor it flies best with a 6x5 on 2 cells. More rpm with 3 cells with a 5X4.3,  but not as much thrust. On the 6x5 the plane stunts about as well as it did with the Black Widow, not that that was very good anyway. I think the motor would fly any of the Brodak 1/2A models with built up wings just fine.
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Offline Tim Wescott

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Re: Change from gas to electric
« Reply #9 on: May 17, 2010, 11:34:49 PM »
Quote from: Mike Anderson on May 13, 2010, 01:44:23 PM
John - a 2210 size motor is very small.  A very broad-stroked explanation is that the '22' part is the diameter and the '10' part is the length (in millimeters), but some mfrs. measure the outside dimensions and some measure the stator (windings) when assigning those numbers, so one person's 22 is another persons 28 or so.  As another example, an Axi 2826 and a Turnigy 3548 are roughly the same size and weight.

In this instance, I think that Dennis is refering to a motor that is in the 1/2A power range, since the model that was inquired about is only 31" span.  However, after seeing that the original was powered with a .23, I think something in the 300 Watt range ( A Turnigy 3536 with a 3-cell battery) would turn about a 9" prop at about the same RPM as the .23 glow.
The plans call out a .23 ignition engine, 1948-style.  That's a lot different from a modern .23 glow, and a lot heavier when you take the ignition system into account.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Tim Wescott

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Re: Change from gas to electric
« Reply #10 on: May 18, 2010, 12:19:53 AM »
My intuition tells me that with careful wood selection and minor redesign you could build the model to weigh 14-18 ounces with glow power and a full tank of fuel.  Build it with medium and hard balsa and stick a .23 in there with all the old-style ignition doo-dads and I bet it'll weigh two pounds.

  • Use contest balsa for those slabs of 1/4" on the sides, or laminate balsa onto foam
  • And maybe for the top block between the wings, exercising all due respect for the fact that it's weight bearing.  (Note that the struts are also weight bearing).
  • Replace the back two formers with 1/16" ply, or lite ply
  • Use balsa for the tail -- either hard C grain 3/32", or medium 1/8"
  • If you're lucky and the motor is short, mount it to the firewall with a spacer.  If you're not lucky and the motor is long, make the firewall into a ring to carry the cowl mounts, put a bulkhead in to carry the motor, and mount the motor to that

Otherwise build it to the plans.  Plan your battery location -- I think you want it above the bellcrank (maybe hang the bellcrank from its former instead of putting it on top).  I think that finding a home for the battery is going to be your toughest task; get that figured out and you're probably doing just fine.  Remember that you want it removable for charging.  Weigh everything.  I'd allow no more than eight ounces for the structure, including the control system, and another two for the finish.  You ought to be able to hold it down harder than that, but this style of construction is new to me ('cause I'm not old enough!).

Once you know how heavy it's shaping up to be then choose a motor.  If you can select a CL motor based on RC practice, then it looks like you want a hot 400 or a 480 (100 to 150 watts) -- but I'm not good at sizing motors for electric CL!  Hopefully my obvious ignorance will spark someone who actually knows to say something!!
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mike Anderson

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Re: Change from gas to electric
« Reply #11 on: May 18, 2010, 07:47:20 AM »
Quote from: Tim Wescott on May 17, 2010, 11:34:49 PM
The plans call out a .23 ignition engine, 1948-style.  That's a lot different from a modern .23 glow, and a lot heavier when you take the ignition system into account.

Yeah - something about the power of a sporty .15-.19 glow, or about 300 Watts.  Weight of a 300 Watt electric will be in the same range as an old ignition engine, though it might be distributed somewhat differently.
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Mike@   AMA 10086
Central Iowa

Offline Tim Wescott

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Re: Change from gas to electric
« Reply #12 on: May 18, 2010, 10:28:12 AM »
Quote from: Mike Anderson on May 18, 2010, 07:47:20 AM
Yeah - something about the power of a sporty .15-.19 glow, or about 300 Watts.  Weight of a 300 Watt electric will be in the same range as an old ignition engine, though it might be distributed somewhat differently.
I would have put it at the power of a sporty .10 glow -- keep in mind that this is a piston-port induction, baffled motor running gasoline.  A .10 with Schnuerl porting may well stomp it into the ground.  Need to find all the right engine reviews, and compare horsepower.

I see profile stunt designs for .15-.19 engines running in the 36-42 inch wingspan range; this plane has a 31 inch wingspan.  Assuming that you build light, that would seem to point back to a strong .10 also.

It's all plywood and really thick slab sides, so if you just build it to the plan without regard to weight you may need those 300 watts, though.  And I suppose that I should mention that I always end up underpowering my airplanes on the first cut; you can count on my aim to be a bit low...
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Mike Anderson

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Re: Change from gas to electric
« Reply #13 on: May 18, 2010, 11:28:19 AM »
Well, maybe I should elaborate a bit -- with the electrics, we seldom run them 'wide open', so a 300 watt setup will probably be sport flying at less than peak.  To give a specific example, I have a smallish sport plane of about 360 sq. in., and I'm using what I refer to as a '300 Watt' setup - consists of a BP2814-6 motor (Kv of 1450) on 3 cells and a 40 amp speed control.  It's capable of turning a 9-4 or 9-6 at over 11000 RPM, and would draw about 30 amps doing it (3 cells x 30 amp ~ 300 W).  But if I turn the power down (by way of the timer) and run the prop at say 8500 RPM I would only be drawing about 20 Amp or 200 Watt.  This flies my smallish sport plane on 52' lines and easily has power to fly the stunt pattern.  My estimation is that a .23 gasser would probably be propped in the same range - 9-10 inch props and turn between 8000-9000 RPM.  I could well be overestimating it, but better to over power and back off then underpower and have to buy new equipment.

The scale model in question would no doubt fly using a glow .10  - .12, but I think most of us would drop in a .15 - .19 and back it off, if necessary.  The real problem will be, as you have mentioned, getting a scale model with a rather short nose and long tail to balance with modern engines or with electric -- I foresee a large lump of lead bolted to the firewall regardless of the electric system chosen.
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Mike@   AMA 10086
Central Iowa

Offline Tim Wescott

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Re: Change from gas to electric
« Reply #14 on: May 18, 2010, 12:29:28 PM »
Quote from: Mike Anderson on May 18, 2010, 11:28:19 AM
Well, maybe I should elaborate a bit -- with the electrics, we seldom run them 'wide open', so a 300 watt setup will probably be sport flying at less than peak.  To give a specific example, I have a smallish sport plane of about 360 sq. in., and I'm using what I refer to as a '300 Watt' setup.
But, but, but...

This thing only has an area of around 150 squares -- if you're putting a 300 watt setup into a plane with 360 squares, then surely you'd want to start with something smaller for such a smaller plane.

Because on the one hand you certainly don't want to start too small, and have to buy new equipment -- but on the other hand you don't want to weigh the whole thing down with an unnecessarily huge power system.

OTOH, if Ted knows he builds heavy (or if he wants to replicate the whole "brick on a string" theme of the original) then your 300 watt setup may be the way to go.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

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