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Jul 22, 2019, 07:22 AM
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Sig Riser 100 Conversion to Electric


I just purchased a Sig Riser 100 kit and would like to build it with electric power. There have seen a number of older posts on the subject but the way the electric motor technology is constantly improving, I'd like to hear from some of you more experienced folks out there, as what might be the best electric set up for this glider. I'm not looking to make it a hot liner but rather a fairly decent climber with a long flight capability. I'm hoping to power it with maybe a 3s 1300 battery to try and keep the weight down. Any comments will be appreciated.
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Jul 23, 2019, 08:07 AM
3RN13
ernie b's Avatar
Good morning Wayne

I am also building and converting a Riser 100 to electric, the airframe is in the bones and I may wait until Winter to start work on it again but I have my eye on two possible power systems.

Turnigy 540L V-Spec inrunner W/Impeller 810kv at 158g and the Turnigy Gliderdrive SK3 Competition Series-3858-4.6 840kv at 180g both cost about $40.

The main advantage is the inrunner and "outrunner in a can" have leads that exit out the rear of the motor and make for an easy and powerful install.

Ernie
Jul 23, 2019, 09:37 AM
Mesa AZ, it's a dry heat!

Motor choice


The model should weigh 2-2.5 lbs ready to fly so 300 to 350 Watts should work well for this model. The Gliderdrive would be a good choice on 3s. Final tuning can be done with prop size.
I have an article on choosing a power source on my blog. Just click on my name on the left of this message.

Regards

Iain
Jul 23, 2019, 03:20 PM
Registered User
I built one and using an Axi 2820/14 Long version for gliders.
http://www.espritmodel.com/axi-25-28...-motor-v2.aspx
Jul 23, 2019, 07:30 PM
B for Bruce
BMatthews's Avatar
Quote:
Originally Posted by rev.iain
The model should weigh 2-2.5 lbs ready to fly so 300 to 350 Watts should work well for this model. The Gliderdrive would be a good choice on 3s. Final tuning can be done with prop size.
I have an article on choosing a power source on my blog. Just click on my name on the left of this message.

Regards

Iain
That much power will easily ensure it can climb away vertically. If that is what you want then fine. But from the original post you sound like you want a solid but not vertical climb at full power. Would a climb angle of around 45 degrees be OK? And reaching around 400 feet in roughly 45 to 50 seconds? If so then you can get away with a LOT less power. Something more in the line with around 60 to 70 watts per lb of model weight. And for a 2.5lb flying weight that means something like 150 to maybe 180 watts total to the motor and prop. And to aid with avoiding issues of overheating the motor a max power rating for the motor of 200 to 240 watts.... along with ensuring at least a minimal airflow through the motor. You'd also want a relatively low Kv value to ensure the motor can swing a good size prop. Something around 1000 or so.

Motors of this sort of size are easily found and quite light and would be quite happy feeding off a battery of the size you suggested.
Jul 23, 2019, 11:51 PM
Groundloop World Champion
old_dude's Avatar
Here is a modification that was suggested for modifying a Riser 100 for e-power.
I am unable to find the article for more detail. I would be cautious about shortening
the nose moment for e-power. Build the fuselage last and do a mock up with the
components, motor, battery, ESC, servos, receiver in approximate position including the
vertical and horizontal stabilizers, and wings in place first. This will give you a
good approximation of the center of gravity. Don't forget spinner and prop.

Old_dude
Jul 24, 2019, 12:32 AM
Registered User
scirocco's Avatar
IMO great advice in the last 2 posts.
Joining the two together a bit, sometimes it can help to use motor weight as a factor in assisting the conversion, especially if design modifications are to be minimised.
I agree with BMatthews power requirements analysis, so I'd use that to indicate the minimum size motor that could handle the power - around 60+80g. Then I'd look at how balance is working out and if nose weight is needed allocate extra weight to the motor rather than use a minimum size motor and heavier batteries and/or ballast. This approach will minimise total weight and also give you an understressed motor.

Even if a larger motor could handle more I'd prop it to the lesser of the power target or whatever current the battery or ESC can readily handle.

A bigger motor might drive you to Kv well below 1000rpm/V, but you should have the freedom to increase prop diameter and pitch to compensate. Obviously there are physical limits to the size motor that will fit, but at the clean sheet stage it's worth a thought.

Re battery sizing IMO 3S 1300 is more than adequate from current (30A easily) and number of climbs perspectives and I'd only use bigger if needed to balance. At below 300W even 3s 850-1000mah is worth considering. I'd rather soar with less weight and change packs after 4 climbs than lug a big battery around.
Last edited by scirocco; Jul 24, 2019 at 12:41 AM. Reason: Clicked post too soon
Jul 24, 2019, 03:39 AM
Registered User
I agree that 75 watts per pound is enough, unless you want to fly in ALES contests at the 200 meter setting. I seem to recall having a moderatly heavy 2 meter, which probably means at least 35 ounces, with a brushed, geared motor and a 7 cell nicad (nominal 8.4 volts), and probably 18 amps. Worked fine, but climbs were probably over a minute. I had another, small model which did fine on about 40 or 50 watts per lb, but that had a lower wing loading than a Riser 100 is likely to have.

For ALES, I think 100 watts per lb is good if you have a prop that's well matched to the motor.

One might consider a little more power with a slightly smaller prop, for less drag in the glide. Don't go too far with this or it will be noisy.

If you're going to do a lot of powered cruising around, a 3S 1300 might not be enough for long duration, but I'm sure it's enough for two or three quick climbs followed by actual soaring, and is probably what I'd use for this sort of model.

If I was doing one of these, and it seemed like it would need a lot of nose weight, I might use one of my ancient brushed, geared motors. But I'm a Luddite. Even then, I doubt I'd go out and buy such a motor.
Aug 06, 2019, 08:36 PM
Registered User
John Gallagher's Avatar
Quote:
Originally Posted by old_dude
Here is a modification that was suggested for modifying a Riser 100 for e-power.
I am unable to find the article for more detail. I would be cautious about shortening
the nose moment for e-power. Build the fuselage last and do a mock up with the
components, motor, battery, ESC, servos, receiver in approximate position including the
vertical and horizontal stabilizers, and wings in place first. This will give you a
good approximation of the center of gravity. Don't forget spinner and prop.

Old_dude
I remember this and after the builder shortened the nose he had to add a few ounces lead ballast in the nose to get it to balance.
Aug 09, 2019, 12:37 PM
B for Bruce
BMatthews's Avatar
We gotta be careful when looking at nose jobs on older designs such as this. The Riser has been around for a LONG time and some of the electric nose mods date back to the age of big heavy ferrite can motors and heavy NiCad battery packs. And at that time short noses made sense.

It was also a time when nearly everyone used flight batteries that were made from four AA NiCad cells and which weighed and even 4 oz. These days we can typically find a motor, ESC and suitable lipo pack which is roughly 4 oz in total. So there's no need or desire to shorten the nose since we're replacing that 4 oz battery pack with stuff that is spread out a little more. In fact I'd say it's more important than ever to keep the tail good and light.
Aug 09, 2019, 12:57 PM
Registered User
Mike-O's Avatar
I built an electric fuselage for my Riser 100 earlier this year. I should point out that the weight estimates in this thread are low - the pure glider version is listed as 45-49 oz on the box. My pure glider version was 50 oz. The electrified version is 64 oz.

This was a totaly new fuselage - craft store plywood in the front and 1/8 " balsa in the back, with none of the lightening holes in the back half.

I had a Hacker A3012XL V4 (900) sitting around which I had bought for a future project (not this one), so I put it to use here since the motor calculator said it would work fine.

Used an Aeronaut 12x6.5 prop. Battery is a 1650 mAh 75C 3 cell. I'm sure you can get by with less motor than this since vertical climbs are possible. The battery was fine for this set-up.

The plane came out pretty nose heavy even with a slightly shortened nose. I did not need to add any tail weight, but the battery, reciever and servos are all located under the wing, as far back as they could go.

See attached photos - good luck with yours.

Mike
Sep 24, 2019, 10:17 AM
3RN13
ernie b's Avatar
Awaiting maiden flight, but here is my Riser 100.
Weather has been wet and windy...waiting patiently for Mother Nature.

AUW - 55oz

Ernie
Sep 24, 2019, 11:10 AM
Registered User
I live north of you....Northern Michigan and the weather up here hasn't been any better. Today is nice but once again the weather is going to close in.
At least we don't have the problems of those in and around Houston.
I did not make any mods to the fuse of my Riser for electric power.
Sep 24, 2019, 11:47 AM
3RN13
ernie b's Avatar
Quote:
Originally Posted by jollyroger
I live north of you....Northern Michigan and the weather up here hasn't been any better. Today is nice but once again the weather is going to close in.
At least we don't have the problems of those in and around Houston.
I did not make any mods to the fuse of my Riser for electric power.
Good morning Mr. Jollyroger

I made only one minor change to take some tail weight out of the fuselage.
I used the Turnigy 540L V-Spec inrunner W/Impeller 810kv, a 40 amp ESC and a 3S 2200 battery so my wing loading should be right around 7.8 oz/sqft.
A Winter project may be to put the spoilers in...we'll see.

Ernie
Sep 24, 2019, 03:12 PM
Registered User
I'm using some micro servos for the spoilers and found I needed a "Y" with a booster but it doesn't take much to get the ship on the ground.
I built a DJ Aerotech Chrysallis with spoilers and only use them when nearing touchdown.
My Riser uses an Axi , 2820/14 special design for sail planes.
http://www.espritmodel.com/axi-25-28...-motor-v2.aspx


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