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480 size inrunner replacment??

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Corsair01508/09/2017 04:13:27
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13 forum posts

I am doing RCM&E handley page O/400 plan that requires 2, 480 brushed inrunners. But I am having a hard time trying to figure out what equivalent outrunner I will need.

Is there a formula or something?

here are the specs if that helps:

The wingspan is 1600mm and the fuselage length is 1092mm.

all up weight is about 35-45oz

Percy Verance08/09/2017 06:38:25
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8108 forum posts
155 photos

Have a word with George at 4 Max (Purple Power) Models, he'll sort you out. He has specific sizes of brushless motor equivalents for the old brushed types.

 

Edited By Percy Verance on 08/09/2017 06:38:57

Piers Bowlan08/09/2017 06:54:00
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1882 forum posts
45 photos

Caleb, you probably found this discussion on the forum about the model. I dug out my plan of Cyril Carr's HP0/400 from Nov 2012, it looks like an interesting project. The old brushed 480 motors were heavy and not very efficient and if I recall correctly were only good for about 80W without melting? Being depron the model is very light, Cyril says his was 31oz on the data sheet in the magazine article. With 2.84 sq. ft of wing area I make that about 11oz per squ ft. or not very much at all! With an all up weight of 2 lbs and working on 100W per lbs that is 100W per motor. As it is so light I think it would be ballistic on this so perhaps 50-100W might be more appropriate? Having said that, with all that rigging it looks like a draggy model.

In the discussion they were talking about 1350kv to 1450kv motors but this was to keep the prop diameter down to 6in plus they were using scale 4 blade props. This seems a rather high kv to me for a lightly loaded slow flying model so perhaps 1000kv-1200kv might seem more appropriate plus I would use two bladed props as they are more efficient. I would also consider moving the engines nacelles out a tad to accommodate the larger props if necessary (I am not a purist, and in the air you won't notice). Hopefully someone else will be along in a moment who has more experience than me.

As far as motor choice is concerned how about two of these with 8in X 4in two blade props - you will have to move the motors 'out' by about an inch to achieve the prop clearance, like I said. Alternatively a higher kv motor would enable you to use a slightly smaller prop on a 3s LiPo, possibly one of these?

If all else fails you could give 4-Max a ring as they can probably make some sensible suggestions of what motors to use.

(you beat me to it Percy!)

Edited By Piers Bowlan on 08/09/2017 07:12:11

Corsair01508/09/2017 08:19:18
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13 forum posts
Posted by Piers Bowlan on 08/09/2017 06:54:00:

Caleb, you probably found this discussion on the forum about the model. I dug out my plan of Cyril Carr's HP0/400 from Nov 2012, it looks like an interesting project. The old brushed 480 motors were heavy and not very efficient and if I recall correctly were only good for about 80W without melting? Being depron the model is very light, Cyril says his was 31oz on the data sheet in the magazine article. With 2.84 sq. ft of wing area I make that about 11oz per squ ft. or not very much at all! With an all up weight of 2 lbs and working on 100W per lbs that is 100W per motor. As it is so light I think it would be ballistic on this so perhaps 50-100W might be more appropriate? Having said that, with all that rigging it looks like a draggy model.

In the discussion they were talking about 1350kv to 1450kv motors but this was to keep the prop diameter down to 6in plus they were using scale 4 blade props. This seems a rather high kv to me for a lightly loaded slow flying model so perhaps 1000kv-1200kv might seem more appropriate plus I would use two bladed props as they are more efficient. I would also consider moving the engines nacelles out a tad to accommodate the larger props if necessary (I am not a purist, and in the air you won't notice). Hopefully someone else will be along in a moment who has more experience than me.

As far as motor choice is concerned how about two of these with 8in X 4in two blade props - you will have to move the motors 'out' by about an inch to achieve the prop clearance, like I said. Alternatively a higher kv motor would enable you to use a slightly smaller prop on a 3s LiPo, possibly one of these?

If all else fails you could give 4-Max a ring as they can probably make some sensible suggestions of what motors to use.

(you beat me to it Percy!)

Edited By Piers Bowlan on 08/09/2017 07:12:11

Ahh, thanks.

Mine will be a bit heavier since it is being made out of foamboard. (heavier, but more durable. Plus, I cant find any depron ;D)

I think I will go with 4 blades and about 90-100W and around 1100kv, as I think I will need the extra power.

Thanks for both of your help!

Denis Watkins08/09/2017 08:26:11
3911 forum posts
61 photos

At 3 1/2 lb, sport flying would be approx 350W total, so should you look to a little more power.

Piers Bowlan08/09/2017 08:41:00
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1882 forum posts
45 photos

Foamboard sounds good but can be expensive here in the UK, you can buy it for a dollar a sheet in the U.S. I hear! Good luck with the project. yes

Corsair01508/09/2017 09:38:47
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13 forum posts
Posted by Denis Watkins on 08/09/2017 08:26:11:

At 3 1/2 lb, sport flying would be approx 350W total, so should you look to a little more power.

I just want a scale flier, would 100-120W and 1200kv be enough for a scale like flight?

Corsair01508/09/2017 09:42:00
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13 forum posts
Posted by Piers Bowlan on 08/09/2017 08:41:00:

Foamboard sounds good but can be expensive here in the UK, you can buy it for a dollar a sheet in the U.S. I hear! Good luck with the project. yes

Thanks! We are documenting it on our RC channel.

here is the link: https://www.youtube.com/channel/UCAPH8BxNr3bZGVxmkHdxMqQ

The first video (part one of the build) is a bit all over the place (its more of a build montage), but part 2 will have all the stats and information about the build. (like a proper Vlog)

Corsair01508/09/2017 09:43:11
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13 forum posts

Oh, BTW, I live in New Zealand. The foamboard (30x40inch) over here cost about 10 US dollars a sheet!

Piers Bowlan08/09/2017 13:29:50
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1882 forum posts
45 photos
Posted by Denis Watkins on 08/09/2017 08:26:11:

'At 3 1/2 lb, sport flying would be approx 350W total, so should you look to a little more power.'

Three and a half lbs is 56oz Denis! I personally doubt using foamboard would almost double the weight of Cyril's original depron model, especially as most of the weight is in the electronics. Also Cyril's model used two heavy 480 brushed motors and NiCd batteries! I doubt Caleb's model will be significantly heavier and 350w would monster the old HP 0/400!

Denis Watkins08/09/2017 14:01:15
3911 forum posts
61 photos

Woops, sorry guys, I was adding all and sundry to the model as I assumed a bare but large airframe.

Normal flight of 100W per lb is of course adequate. Thanks Piers

Corsair01508/09/2017 20:40:06
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13 forum posts
Posted by Denis Watkins on 08/09/2017 14:01:15:

Woops, sorry guys, I was adding all and sundry to the model as I assumed a bare but large airframe.

Normal flight of 100W per lb is of course adequate. Thanks Piers

Perfect! Thanks!

I am doing this HP O/400 in a captured German scheme I found in the magazine.

Am using tamiya spray paints to get a good finish.

Cant wait to see how it turns out!

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