Topic: Speedline Shannon Lifeboat - obtaining maximum potential from the Jet drives. (Read 22637 times)

kinmel · « **Reply #50 on:** January 05, 2018, 07:42:38 am »

Quote from: C-3PO on January 04, 2018, 11:29:20 pm

Kinmel has agreed to an experiment...

We are going to try and glean some operating data from his Shannon to better understand what is happening when is it on the boating lake.

This will involve mounting a small "data logger" on his boat that will record data to an SD card that can then be analysed/graphed after a sailing session.

Using a real time clock on the data logger and hopefully recording video we can get a better picture of what is happening (map data to video timeline).

We intend to capture:
Date & time
Throttle positions x 2
Bucket positions x 2
Trim tabs positions x 2
ESC temperature x2
Motor temperature x 2
Using an onboard GPS the speed of travel over the water
Using a sensor the pitch and roll of the hull
This might help unravel for example if there is a point where the motors are running faster than the water can get through the jets

On the other hand it might be a complete waste of time...

An interesting experiment
C-3PO

So that is what you meant by " I will send you a board over next week "

kinmel · « **Reply #51 on:** January 05, 2018, 08:32:09 am »

Quote from: Colin Bishop on January 04, 2018, 11:26:54 pm

Gosh! Wasn't it simpler when you just had a prop and a rudder to worry about?

Makes you wonder about the benefits of modern technology.

Colin

It was simpler and achieved far less. No going sideways, no stopping in your own length in an emergency and certainly not managing 32knots !

In truth this project is because the Shannon is totally different to everything else we modellers sail and modern technology let's us manage it without the necessary months of training. Cox helm the boat literally through the seat of their pants; the boat moves and their fingers instinctively react, while we stand on the side of the lake.

We have a choice of learning all those separate control actions that make up a manoeuvre and move between them without really thinking, or we let modern technology sort out the necessary controls and we enjoy boating.

mikew · « **Reply #52 on:** January 05, 2018, 08:40:03 am »

Well I think its fascinating, Maybe one day

McGherkin · « **Reply #53 on:** January 05, 2018, 09:23:56 am »

Quote from: Colin Bishop on January 04, 2018, 11:26:54 pm

Gosh! Wasn't it simpler when you just had a prop and a rudder to worry about?

Makes you wonder about the benefits of modern technology.

Colin

To be honest, once you get the hang of it it’s not that hard. In fact, not much different to boats with seperate engine and gearbox controls!

C-3PO · « **Reply #54 on:** January 05, 2018, 10:25:54 am »

Quote from: McGherkin on January 05, 2018, 09:23:56 am

To be honest, once you get the hang of it it’s not that hard. In fact, not much different to boats with seperate engine and gearbox controls!

My experience with my Pibber using 2 x Kehrer KMB jet 28 drives is that I got caught out on several occasions by putting the throttle into reverse - no clever modules in place

It was only when I got a more sophisticated tranny that I could set the range of output to stop ESC seeing a signal instructing it to reverse the motor.

McGherkin - What model/jet drives/radio setup have you used that you got the hang of and how did you control it?

C-3PO

McGherkin · « **Reply #55 on:** January 05, 2018, 10:36:45 am »

Oh, I was talking full scale. Same as the shannons, morse levers for throttle and morse levers for buckets, wheel for steering.

derekwarner · « **Reply #56 on:** January 05, 2018, 09:53:43 pm »

Question for Kim - CC

The control path these guys [C-3PO & kinmel] are going is bordering on flying a twin engined helicopter

......

eg.,

We intend to capture:
•Date & time
•Throttle positions x 2
•Bucket positions x 2
•Trim tabs positions x 2
•ESC temperature x2
•Motor temperature x 2
•Using an onboard GPS the speed of travel over the water
•Using a sensor the pitch and roll of the hull

These certainly appear all valid criteria.......did you ever experience any such conceptual ideas in control of your build?

Have also sent this via PM.......just in case you miss it here

Derek

Derek

C-3PO · « **Reply #57 on:** January 06, 2018, 08:20:44 am »

Talking of helicopters...

@ 30000rpm https://www.youtube.com/watch?v=wiGSIVZjqrA

I have 2 of these Graupner Jet 5's sitting on a shelf - Hmmm...

C-3PO

C-3PO · « **Reply #58 on:** January 07, 2018, 08:14:27 pm »

Quote from: kinmel on January 07, 2018, 08:30:31 am

The stern water line seems crucial- the stationary boat has to be deep enough in the water for the impeller to be fully submerged and there is not a lot of leeway between too high and too low.

This is certainly something I found with my Moonraker. The sweet spot is quite narrow and the trim tabs are significant

Perhaps Alex (IKB) could throw some light on this aspect through his work with 3D printed jet drives or TomHugill as his Moonraker doesn't hang around on the water...

This from Alex a while back

http://www.modelboatmayhem.co.uk/forum/index.php/topic,53340.msg604800.html#msg604800

Quote

But my main question relates to the vertical positioning of the water jet output - what's best/acceptable to get the maximum thrust from the water expelled from the drive - the drive exhaust submerged under water / above water or something else?

From Alex
http://www.modelboatmayhem.co.uk/forum/index.php/topic,53340.msg604810.html#msg604810

Quote

C-3PO - You are correct, at rest, the jet unit needs to be at least half submerged in order to reliably self prime, once underway, the whole transom tends to become exposed at high speed, so the jet is just exhausting into air, most commercial units usually have a 3-5 degree angle pointing down from the horizontal to point the stream into the water, as this will produce more thrust.

C-3PO

C-3PO · « **Reply #59 on:** January 07, 2018, 08:52:36 pm »

Data Logger

These boards will stack on top of each other....

C-3PO

Flundle (Speedline Models) · « **Reply #60 on:** January 10, 2018, 01:01:49 pm »

What I need is a go on a real one.
I said " WHAT I NEED IS A GO ON A REAL ONE"
I SAID......."WHAT I NEED IS A GO ON A REAL ONE"
I SAID......."WHAT I NEED IS A GO ON A REAL ONE"

(Phew! throat hurts now)

[/size]I SAID......."WHAT I NEED IS A GO ON A REAL ONE"
Well, if you dont ask, you dont get!
Quetly then, I am hoping someone around the Mersey might hear this..............?
Adrian

Neil · « **Reply #61 on:** January 10, 2018, 04:47:48 pm »

get yourself up to st annes tomorrow Adrian............training on the SLARS starts in the morning with the Shannon, which is in the dock at Fleetwood at the moment..........they are bringing the boat around tonight to upload onto the supacat and put it into the lifeboat station, vacated by the Mersey.

Neil · « **Reply #62 on:** January 10, 2018, 04:51:57 pm »

the new Shannon for st annes arrives on 28th feb is to be called RNLB BARBARA ANN.

Flundle (Speedline Models) · « **Reply #63 on:** January 10, 2018, 05:39:45 pm »

Bit sad to see the Mersey go.

Neil · « **Reply #64 on:** January 10, 2018, 09:24:30 pm »

yeh, so do I..........lovely boats...........but I don't think the Queen, whom it is named after and personally by her..........would like the old girl sat out in the cold wet fog for the next two months by a usurper taking her place in the boat house

The beast arrived tonight through the fog to pave the way for THE QUEEN's replacement.

TomHugill · « **Reply #65 on:** January 11, 2018, 08:22:19 am »

Odd my post seems to have been deleted along with the reply :/

C-3PO · « **Reply #66 on:** January 11, 2018, 06:17:55 pm »

Making progress on the data logger.

Thought it would be neat to see if summary telemetry data could be streamed ashore as well as full dataset captured to SD card.

This would allow real time data to be monitored.

The proposed shore based screen shows:

S: current speed in cm per second ( wanted to use a unit that would make small changes very visibble)
T: trip speed - fastest speed recorded since power on
S: GPS number of satellites being received
Fy - GPS Fix - yes/no

T:15001500 - the throttle output x2 from the RX
R:15001500 - the rudder output x2 from the RX
B:15001500 - the bucket output x2 from the RX
R:15001500 - the trim tab output x2 from the RX

Temperatures for motors and ESC's Port Motor / Port ESC / Starboard ESC / Starboard Motor

C-3PO

McGherkin · « **Reply #67 on:** January 12, 2018, 12:35:41 am »

Very nice work!

C-3PO · « **Reply #68 on:** February 08, 2018, 12:27:59 pm »

Update on Shannon Data logger

Well after lots of head scratching and migrating from Arduino to Teensy running Arduino code

Boxes arrrived today - tidy up everything from prototype spaghetti to finsihed product and fit in box, final test and ship to Alan for the interesting part!

@ the Shore - telemetry

@ onboard the vessel - sensor data capture to SD card / transmit telemetry to shore

T33cno · « **Reply #69 on:** February 08, 2018, 12:28:43 pm »

Fantastic

furball · « **Reply #70 on:** February 08, 2018, 12:57:04 pm »

Silly question, but what's the resolution on the GPS module? I.e. will it measure the (relatively) small distances a model boat will travel - I presume so, otherwise you wouldn't be using it.

Just interested to see if it's worth putting into something I'm playing with.

Lance

C-3PO · « **Reply #71 on:** February 08, 2018, 01:46:51 pm »

Hi Lance,

I am not sure of the resolution. You can research accuracy here https://www.gps.gov/systems/gps/performance/accuracy/

The GPS unit I am using is this - https://www.adafruit.com/product/746

The GPS outputs standard National Marine Electronics Association (NEMA) sentences - simply give it power, a view of the sky and the serial data starts to pour out of the device

You can get info about NEMA here - http://www.gpsinformation.org/dale/nmea.htm

The video below is by a guy called Jeremy Blum - one clever guy!! - it might give you an idea of the resolution when he maps the data

https://www.youtube.com/watch?v=TtZEZYQG0xk @43 mins - this is quite an old video and I would guess there will be a different way to do this by now

By recording GPS sentence output you can easily map the path taken on Google Earth or GPS Visualiser etc

C-3PO

kinmel · « **Reply #72 on:** February 08, 2018, 02:21:28 pm »

You have certainly worked hard on this Jonathan, thank you.

So what data trials do you all want to see?

We have the supplied Propdrive 35-42 1250Kv 800w T14 motors and also Turnigy SK3 35-42 1250Kv 755w T10 Motors

S3 and S4 Lipos

Trim tabs - fully variable, or 3 set positions

We will post the draw data on here and you can work it out yourself, or be like me and wait for Jonathan

Stavros · « **Reply #73 on:** February 08, 2018, 06:19:21 pm »

Playing devils advocate here We know the motors that have been supplied are the correct ones for hte jet drives BUT what is the MAX rpm of the jet drive unit as suerly if you go over the max reccomended rpm of this all you will encounter is pure cavitation inside the unit.....just athought....Reason for asking is that I have a Graupener jet drive and it is reccomended that no motor above 700watts is used

Dave

C-3PO · « **Reply #74 on:** February 08, 2018, 06:48:30 pm »

This is an attempt to unravel what might be going on.

It's possible that we may get data that shows that you advance the throttle from X to Y and you get no increased speed but likely hotter ESC's and motors - this maybe due to cavitation as you mention.

This may prove to be a fascinating experiment that yields great results and understanding or a complete waste of time and energy (and my brain cells)

Dave (The Old Fart) retro fitted trim tabs to his Tamar and reported a noticeable improvement in performance.

I will shortly pass the mantle to Kinmel who will collect the raw data so we can all see if this approach yields any positive results

C-3PO

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Author Topic: Speedline Shannon Lifeboat - obtaining maximum potential from the Jet drives. (Read 22637 times)

T33cno

Stavros