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Author Topic: 1/12 SRN6  (Read 2017 times)

TomHugill

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1/12 SRN6
« on: December 11, 2016, 03:59:40 PM »



Firstly I can't take any credit for this, I bought it part built off live steam enthusiast that had run out of inspiration to finish it. I did some minor work to it and Woz 3D printed me a lift fan. Sadly this was where the project stalled.


That is till a chap called Dave in Dover offered to finish her for me.


Scale is roughly 1:12, it's a big beast over a meter long. I'm taking delivery next week all being well so I'll get some more footage then.


Some pictures of how she's progressed.


As I bought her:











To this:

























I picked it up from Dover and got it home with the help of HS1 and virgin trains (had afew intresting looks carrying it from St Pancras to Euston and through Manchester!). First test showed the lift fan was doing the job  and it was hovering well on 3s. The thrust however was lacking, it moved ok on a flat surface but didn't have the omph to make quick course corrections, struggled over rough transitions and didn't respond well to steering. Also I was getting a fair bit of vibration through the coupler (which was solid) and the drive shaft.


First item on the agenda was a new thrust motor as the existing one couldn't updated  to 3s. Whilst I was at it I figured I would get bigger lift motor. Mated to these are two 80a fan cooled esc.








New vs old.


Yet to run it for any length of time so we will see how run times are. Currently using 2 3s 5ah lipos, one for lift and one for thrust. Should the lift motor be drain the battery too quickly I have another pack which I can add to bring it upto 10ah.





Here's a quick video of it with new motive power


[video]https://youtu.be/1dDrMyGDzy4[/video]


I stripped out the old drive shaft and coupler and got a new one made to the correct size. Using the solid coupler to get the alignment right before I glued everything in, then using a a coupler with a rubber insert to reduce vibration.





New lift motor installed





As she's stands now








Unfortunately I'm still a "xxxxx" poor pilot and had a little accident involving going sideways into next doors car :(





But she's now back together and ready for an inaugural trip on the lake.

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Big Ada

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Re: 1/12 SRN6
« Reply #1 on: December 11, 2016, 05:57:07 PM »

So you live somewhere in the Manchester area.
It always helps if you put that sort of thing in your Profile.

Len, Model Boat Association Dover, Scale Secretary.
I am building a Griffon 2000TDX Hovercraft at the Moment.
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ballastanksian

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Re: 1/12 SRN6
« Reply #2 on: December 11, 2016, 08:13:03 PM »

Gorgeous model Tom  :-))
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Sub driver

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Re: 1/12 SRN6
« Reply #3 on: December 14, 2016, 12:04:00 AM »

Hi Tom.
I was wondering if you had done anything with that, you should find that you use more of the thrust battery than the lift one as you can usually back of the lift motor quite considerably once you have built up the air pressure in the skirt and Plenum chamber as you need only replace the air that is leaking between the skirt edge and the medium you are running on where you will use a lot of thrust 90% of the time.
On my hovercraft models i usually use two thrust batteries to one lift battery due to this.
What is the size of the 4 bladed prop ?
With an 1800kv motor on 11.1v i would think the prop range would be an 8x4 or 7x3  Two bladed prop for max thrust with a 4 blade you generally go down a size and pitch to take into account of the extra blades....just a thought ...dont want you to over prop the motor and fry it....i have seen this done at our lake motor went up in smoke...due to overpropping it  O0
Regards Sub
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TomHugill

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Re: 1/12 SRN6
« Reply #4 on: December 14, 2016, 12:43:33 PM »

Hey Chris, intresting observations regarding the lift fan, I've only briefly tried it on the lake in unfavourable conditions so more testing will be needed. The prop is a 10x6 cut down to 9". I'm using an NTM 3536 motor, seems to have a fair bit more grunt than the only one (should do at 3x stated power of the old one!). It was warm but not boiling after my run so should hopefully be ok
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Klunk

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Re: 1/12 SRN6
« Reply #5 on: December 14, 2016, 01:35:06 PM »

hi tom...........i have a couple of hovercraft. We found out a couple years ago that you can play on the ice on the lake with them, but DO NOT STOP! the skirt freezes to the ice very quickly meaning it has to rescued somehow! other than that enjoy learning turn and skid sideways alot. On my fusion 400 i set her up so she turns in her own length, makes for a good show with the public

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Subculture

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Re: 1/12 SRN6
« Reply #6 on: December 14, 2016, 05:09:52 PM »

No experience with hovercraft, but plenty with aero props. Have you balanced the props. If not I would, because that can eliminate a lot of vibration.

Sub driver

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Re: 1/12 SRN6
« Reply #7 on: December 14, 2016, 06:50:30 PM »

Hi Tom.
Thought it was that sort of size...i would be careful withit thats a lot of load for an 1800 kv...
If you read the reviews of that motor they all use two bladed props up to 8" diameter....more blades and size does not mean more thrust...its all about efficiency of the motor and it being able to spin up to its max rpm about 80% ( you can never get 100% efficiency).
I was also going to mention balancing the prop and also it appears to be an ic prop big boss on it...you will gwt more thrust and running time with an electric prop...
Regars sub.
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TomHugill

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Re: 1/12 SRN6
« Reply #8 on: December 14, 2016, 07:10:42 PM »

Hey sub,


Here's the prop I'm using:


http://www.apcprop.com/product_p/lp409060.htm


I'm struggling to find a smaller 4 bladed one, if you've any ideas though they would be appreciated.


I didn't realise there was a difference between electric and ic props.


Andy I've ordered a prop balancer, I've never done it before so wish me luck!

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Sub driver

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Re: 1/12 SRN6
« Reply #9 on: December 14, 2016, 08:13:33 PM »

Hi Tom.
Yep there is a huge diff in ic and electric props the blade is a different shape and a smaller thinner boss the ic ones are that thick to allow for the thump of the explosion in th cylinder where the shock is transmitted through..
An electric motor has to overrcome the inertia of that big boss to start spinning up the prop..
You can get a 6x3 four bladed prop. from Gliders made by Graupner..or flying models in Leeds for info they are left handers (pusher props ) but just reverse two of the brushless motor connections to reverse it.
Also APC and Gemfan do electric props they have an E nxt to the size ebossed on them..if i can i will post a pic of an electric prop nxt to an ic one and you can see the difference its very noticable.
A 7x5 electric two bladed prop is very powerful on a 2200 kv motor on 11.1 volts
Regards Sub.
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Sub driver

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Re: 1/12 SRN6
« Reply #10 on: December 14, 2016, 09:05:49 PM »

Tom.
I/C and elec 7x4 props
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Sub driver

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Re: 1/12 SRN6
« Reply #11 on: December 14, 2016, 09:10:47 PM »

Tom.
A Graupner 6 x 3 (L) four bladed.
Regardd Sub.
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Sub driver

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Re: 1/12 SRN6
« Reply #12 on: December 14, 2016, 09:20:03 PM »

Tom.
Hope the above is of use...if you havnt balanced a prop before i suggest you start with a two blader first as a four blader may confuse you but its the same principle though.
Regarding running on ice i have found that if the lake is completly frozen ie no water left on top of the ice it shouldnt stick however if there is any water there at all or a wet skirt it will do this can be helped by squirting the skirt with silicone spray
Regards Sub.
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Will01

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Re: 1/12 SRN6
« Reply #13 on: February 10, 2017, 09:32:32 PM »

Wow what a lovely build. I am sure there used to be anotified SRN6 nearby Dumfries on the shores of the nit at our end pointo,  but then again knowledge of these craft is very minimal. But your build looks absolutely fantastic. Have you got any videos?
Superb looking fun project
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