Topic: OceanWorks Jet drives for 1:12 scale Shannon Lifeboats (Read 42855 times)

Taranis · « **Reply #50 on:** September 23, 2019, 02:28:05 pm »

No please don't think that

all contributions and suggestions welcomed. If I was doing this for the first time I would definitely use the telemetry and some of us Speedline builders did exactly that as we had nothing to compare from other models.
I do have RPM and Temp readings on my other but the temperature has never been abnormal when I forgot to turn on the cooling pump.
I also don't need RPM now I'm familiar with the motors and batteries.
The most likely reason for not overheating is that they only draw half their current capability at full throttle. I failed to blow 25 amp fuses at continuous full throttle and now don't use fuses either but rely on the ESC internal protection

With this model I want the weight to be the minimum to fit more battery capacity so no frills

dpbarry · « **Reply #51 on:** September 23, 2019, 03:07:26 pm »

Maybe slightly off topic here and probably covering in another thread but what radio system are you using (Name probably says it all

) and what way are you controlling the buckets on the radio independently??

Declan

Taranis · « **Reply #52 on:** September 23, 2019, 03:32:03 pm »

I will cover OpenTX set up in this thread but I have to re learn it first.

Scarborough uses this.

Buckets are on the left and right side levers
Throttle is on left stick (friction) but operating switch S2 (red sleeve) changes to independent throttles on S1 S2 slides

dpbarry · « **Reply #53 on:** September 23, 2019, 03:57:26 pm »

Changing my Radio is something I'm considering at moment but not sure which version to go for at present. I have an old F14 and an FC16. The F14 is the navy version with the twin stick and I've a couple of the Robbe Multi encoder/decoders plus a encoder/decoder from https://cp-elektronik.de/index.php/en/ (not built yet)

I think I need to retire in order to allow me to do the things I want to do rather than shoe-horn all this between wife/work/lifeboat/parents etc

Declan

Taranis · « **Reply #54 on:** September 23, 2019, 04:12:37 pm »

When you retire you'll have even less time

I am very lucky retiring at 61

Right here I've glued two pieces of T bar offcuts to the hull.
The tray is now a sliding fit and won't jump out due to the angle of the T's
Some stops glued at the front end and something removable at the back end will make it sweet to take out.

It should not be an over complicated affair to disassemble, the four swing keepers are easy to undo

I'm thinking the ESC's could go on the tray underside or even fix them to a metal plate right against the hull bottom. That would certainly dissipate any heat being next to the water

kinmel · « **Reply #55 on:** September 23, 2019, 07:37:41 pm »

Quote from: dpbarry on September 23, 2019, 03:07:26 pm

Maybe slightly off topic here and probably covering in another thread but what radio system are you using (Name probably says it all ) and what way are you controlling the buckets on the radio independently??

Declan

OpenTx allows us to change the inputs according to the task.

When my model is cruising, both motors are on the left hand stick. As the model accelerates ahead, the trim tab angle is proportional to the same stick.
Stopping involves dropping the buckets, do it at full power and you can damage the buckets. So when you pull back the left stick a sequence starts 1. the motors stop 2. the trim tabs lift 3. the buckets start to come down and after a very short delay the motors start up again. The model is then reversing and adjusting the stick manages the power and buckets to produce the speed you want.
Different things happen if you select throw a switch for slow manoeuvring, another switch throw will set the controls for crabbing to port, throw the switch the other way and it will crab to starboard.
Right now some of that is a work in progress, but I am getting there.

Taranis · « **Reply #56 on:** September 23, 2019, 10:47:03 pm »

I'm struggling tonight. I have both receivers bound and have the nozzles working and trimmed. With these drives being symmetrical (optional) one rod is pulling while the other is pushing to make a turn. So no servo travel reverser needed but setting the stops is different.
Anyway that is done but the struggle now is the buckets as I cannot get my LS & RS slider switches to operate them so I've given up today

The reason for the nozzles being on independent channels is so the stops can be set for each servo. The channels are then mixed to operate together on the Aileron stick (right horizontal)

Taranis · « **Reply #57 on:** September 23, 2019, 11:54:46 pm »

Some very very good reading

http://www.rc-soar.com/opentx/basics/index.htm

Taranis · « **Reply #58 on:** September 24, 2019, 06:54:16 pm »

A good day was had starting with the cinema and Ad Astra

Yesterdays issue was overcome having not added the sources to mixes.
Now all servos are operating and stops set. Probably set the channel mixes tomorrow.
Currently mounting the ESC's and will program them to run during tomorrow also.
Trim tabs will be here by Friday hopefully and weather permitting could be launched on Sunday

Pictures later

Taranis · « **Reply #59 on:** September 24, 2019, 07:33:47 pm »

A series of pictures showing the sliding equipment tray and the ESC's mounted beneath both with and without deck

mk1 · « **Reply #60 on:** September 25, 2019, 06:22:43 am »

Hi Andy were did you get the 2mm brass servo rod couplers from and also the servo rod keepers.
Thanks John

Taranis · « **Reply #61 on:** September 25, 2019, 08:41:44 am »

Hi John
https://www.ebay.co.uk/itm/25-50pc-Solid-Brass-M2-M3-Hex-Standoff-Spacer-Pillar-Phillips-Pan-Head-Screw-Nut/162046569212?ssPageName=STRK%3AMEBIDX%3AIT&var=461013985820&_trksid=p2057872.m2749.l2649

https://www.ebay.co.uk/itm/Servo-Swing-in-Keepers-2mm-x-8pcs-radio-controlled-aircraft-plastic/172933759880?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Taranis · « **Reply #62 on:** September 25, 2019, 01:21:28 pm »

This morning the Stixall adhesive has set enough to drill & tap for mounting two AE fuse holders. These are 28 amp rated so I will run with a 25 in one and a 30 in the other and learn something when running.

Here the tray is in place with an aluminium bracket fitted nearest centre as a backstop to prevent any movement when servos operate.

Here a view of the receivers mounted to their own plate located with two M3 screws.

Here the first dry run
https://photos.smugmug.com/photos/i-4S4rTjt/0/3c1c1031/1920/i-4S4rTjt-1920.mp4

For the rest of today I will input the mixes for buckets and trim tabs. I may even stick it in the hot tub

Taranis · « **Reply #63 on:** September 25, 2019, 07:06:40 pm »

I found that the supplied couplings are not really suitable and the Stbd side was vibrating.
I have 4mmx5mm solid brass in stock and this has cured the problem

Both changed

derekwarner · « **Reply #64 on:** September 26, 2019, 01:36:12 am »

Andy...I am surprised the manufacturer of the drive kits has included those aluminium CNC spiral helical cut one piece couplings

They are ideal for low speed transmission of rotation with ZERO backlash......typically stepper motor positioning...or in lower power and speed applications the like of Photo Copy machine internal drives etc

At higher speeds, typically 10,000 RPM unloaded, these one piece couplings have been shown to develop harmonic vibrations

Having 2 sets of 2 steel HPGS at 90 degrees [with both pairs in line with each other] in the lighter aluminium body were attributed to this resonance [vibration]

The other issue is the lack of appropriate bore tolerance [ H7] also contributes to off axis securing to the motor shaft

[If the coupling HPGS were tightened at 12.00 and 3.00 o'clock, effectively the coupling body axis is pushed toward the 7.30 o'clock position]

For reference, an H7 tolerance on a hole from 3 mm to 6 mm diameter is + 12 micrometre, - zero]

Derek

Taranis · « **Reply #65 on:** September 26, 2019, 08:25:23 am »

Absolutely spot on Derek
Dave “The old fart” was surprised at seeing them at the onset and he was right.
I have of course told OceanWorks. Hopefully they will be changed in future
The solid couplings were purchased from eBay China when I was building the Speedline as that too had coupling issues. The brass ones can be found very cheaply

This is of course a Research and development subject and changes are being made all the time for future users.
I am dealing with the first unit that was created directly from my requests and they have done very well in a short space of time

Taranis · « **Reply #66 on:** September 26, 2019, 09:10:10 am »

For others but of course if using a motor shaft other than 5mm choose the correct size
Typical example https://www.ebay.co.uk/itm/4mm-to-5mm-RC-Aircraft-Toy-Brass-Motor-Shaft-Coupling-Connector-Coupler-C9B3/283449122243?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D39ffd21070ba46f0987d136b1b772018%26pid%3D100005%26rk%3D3%26rkt%3D4%26sd%3D323711043701%26itm%3D283449122243%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

dpbarry · « **Reply #67 on:** September 26, 2019, 10:03:28 am »

Hi Andy.

At work at moment and reading your thread (on my break

)

Would you happen to know offhand the diameter of the shaft on the impeller. Don't worry if you don't. I can always measure it tonight. Sorry. Scrub this one. Just discovered on the Oceanworkscale website its 4mm

Incidentally, are you using the standard supplied impeller or one I hear being supplied by PropShop?

Declan

Taranis · « **Reply #68 on:** September 26, 2019, 11:02:58 am »

I’m using standard impeller for testing
Prop shop are not making an impeller for this drive. I doubt they know of it but the one they make for Kehrer will fit

Ocean works do all manner of brass propellers for their superb Z drives so an impeller for the jets is a possibility but I guess it depends on how many units they sell

Taranis · « **Reply #69 on:** September 26, 2019, 11:21:03 am »

Right Declan I've asked the question
OW are already playing with more improvements and they will try a 3 blade CNC impeller (not cast bronze)

This is a 2 blade CNC already being considered.

This is the prop shop for KMB drives

dpbarry · « **Reply #70 on:** September 26, 2019, 12:05:09 pm »

Cheers Andy.

Will just stick with what I have at moment but will keep an eye on your developments.

Declan

Taranis · « **Reply #71 on:** September 30, 2019, 10:52:43 pm »

Still waiting for trim tabs but had they arrived it would have made no difference due to the weather.

I have followed up on my idea to make greasing easier with these silicon extensions. This is 4mm bore pipe with a suitable brass sleeve fitted to hold it extra tight over the grease brass stub

Greasing will happen under the upper helm. The pipes coming through the deck where not visible until cabin removed.
https://www.ebay.co.uk/itm/Mobil-Mobilgrease-XHP-222-High-Performance-Grease-Marine-Grease-390g/173699059342?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

derekwarner · « **Reply #72 on:** October 01, 2019, 01:02:33 am »

Andy......checked for an OceanWorks MJ21 WEB site & hopefully a sectional view...but no and very little in general from other full size builders

What type of bearing/bushing [to be lubricated] is located in the jet housing?......just a confused mental image in my mind & not sure if the impeller will create a vortex or low pressure, or a high pressure in the cavity being greased

If it is the latter, you could find lubricant being pressurised back up into the silicone tubes, or if the void is subjected to low pressure, then any lubricant being squeezed into the void being sucked out at a great rate of knots

Also conventional Dow Corning type synthetic Rubber Grease as used in boat trailer wheel bearings is not rated to relatively high temperatures

I suppose it simply comes back to whatever the manufacturer recommends?

Derek

Taranis · « **Reply #73 on:** October 01, 2019, 08:44:00 am »

All I can says is that it’s a far superior design to the Speedline drives post my modifications and I don’t lose grease with those in any dramatic fashion
These have a prop tube with lubrication point similar to that I fitted to the SL units with a sealed bearing at the motor end and a silicon or the like washer at the impeller end
Other than that I have yet to sail and test

The bearing can be seen in a gallery here https://www.oceanworkscale.com/product/28mm-rc-boat-water-jet-with-mjp-reverse-bucket-without-motor/

Taranis · « **Reply #74 on:** October 02, 2019, 06:24:42 pm »

I'm still waiting for the trim tabs but today I have wet tested and I'm well happy that they are endowed with abundant power output with the standard impellers.
Hoping for good weather on Sunday and praying that we are cleared to sail as currently barred due to Algae

A video out of the water, this needs good internet for HD quality

8 channels are required for the basics as the 6 servos all have independent operation and where combined like for nozzle steering they also have independent travel end stops. Then 2 ESC's for separate motor operation.
More channels required for extras.
Using two receivers offers redundancy (The boat will operate on just Port or Starboard to return to operator) and allows a separate ESC 5amp supply from each ESC

https://photos.smugmug.com/photos/i-WrGfCpr/0/a6ae05ba/1920/i-WrGfCpr-1920.mp4

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Author Topic: OceanWorks Jet drives for 1:12 scale Shannon Lifeboats (Read 42855 times)