Thor

[Paul TParticipant @pault84577]

The props have arrived and I am sure that the design will be controversial.

The motors have been mounted on a prototype removable mount

Paul

[Bob Abell 2Participant @bobabell2]

I like the new props, Paul…..They will look very nice on your new look tug boat and will stand out from the crowd

Just the job for the Haydock Show this year

It's a pity they weren't handed?…..Errrr…….They look like injection mouldings to me?

Why not have a chain drive, then you could change the ratio to suit the new prop design?

A speed up looks about right?

Just thinking out loud

Bob

[Paul TParticipant @pault84577]

Hi Bob

Thanks for the prompt and to answer a few obvious questions about the props.

No they aren't injection mouldings, they have been machined from high tensile Nylon 66

They haven't been handed because I didn't want to spend the computer time designing a handed version.

They look like computer cooling fans because that is where the inspiration for the design came from but the pitch and camber of the blades is different.

The central boss is so big because the calculations indicate that these type of blades operate better with a 'dead area' in the centre of the rotating area.

The circular indentations in each unit are the results of the units being balanced.

I hope this helps answer a few questions that the readership might have but if anyone has any technical questions I will be happy to answer them.

 

Bob

Regarding your question about chain drive …there is no need to change the ratio as the props are designed to be fully effective operating on direct drive. 

Paul

Edited By Paul T on 14/07/2014 14:56:32

[ashley needhamParticipant @ashleyneedham69188]

Paul.

1) These are to be shrouded?

2) Will there be a central hydrodynamic fairing for the central flat area in these props, one or both sides? or is the dead area bit coming into play here.

3) they look very cool, bit like a pump jet arrangement on a sub.

4) I will think of somethiing else.

5) ah yes… the motors look almost mundane now, connected as they will be to such exotic exterior hardware.

Ashley

[Colin BishopModerator @colinbishop34627]

Ah! So that explain the new F35 fighter was not able to make it to Farnborough. Somebody pinched the lift fans…

Colin

[Paul TParticipant @pault84577]

Hello Ashley

Yes they will be shrouded in a Kortz type arrangement.

Your assumption regarding the role of the hydrodynamic dead area is correct.

I spent some time researching submarine propulsion simply to compare water density performance results.

The motors do look mundane and they look tiny inside the hull, perhaps I should chrome plate the finished motor mount.

Hi Colin

I wish……but you have given me an idea for getting boats onto the plane faster.

Paul

[mike farrellParticipant @mikefarrell21522]

Hi Paul ,Well I like the motor mount being removable ,now do you think a pair of ESPs could be placed in the same manner so as all maintaince can be do out of the hull. I am failing badly finding some high torque motors .Tried golf club motors but not suitable .Looked at Moxon motors but very expensive for the revs. I want

Never seen props like these but would like to try some.

Having had the plans a few days I spent this Am cutting the front end which has slotted together like a jigsaw as her indoors said when I showed her the finished article Along way to go so must be patient

[Paul TParticipant @pault84577]

Hi Mike

All of the electronics can be placed on a removable tray within the upper superstructure (this is where I intend to position my escs) this leaves space available within the lower hull for ballast.

As for motors you could look at the MFA 850s or I was thinking about getting them from China **LINK** loads of power but not so good on revs

Nice to hear its going together ok

Paul

Edited By Paul T on 14/07/2014 19:32:18

[Bob Abell 2Participant @bobabell2]

Paul

There`s nothing worse than to build an awesome model like Thor…..Only to be accused of using a pair of unknown mundane motors!

Why not use two pairs of mundane motors chained together…..and if necessary, print your own motor labels and tart `em up a bit?………They need to look……A gruesome twosome!

Just being frivilous

Bob

[Paul TParticipant @pault84577]

Hi Bob

The motors might look mundane but they pack a big punch and their power output is matched to the new props so there is no need to 'beef them up' by chaining two of them together.

Do they really need tarting up? I ask this question in all honesty as I belong to the school of less is more and I don't see the point in adding unnecessary frivolities.

Paul

[mike farrellParticipant @mikefarrell21522]

Hi all Cut and out pump base in this morning ,now what a problem . Advice for anyone building (strongly recommended) recommend you build up the bows complete then fit to stringers . Then removed to fit the pump base and refit the bows unit .The pump base will not fit any other way . This is a true jigsaw which will be a joy to build .

I must say it is a very impressive sight and larger than I expected . It will now require very strong motors and decent ESPs Thanks to Paul for guidance re motors

To Bob well I will be blinging up my hull with a paint job with girders hand painted by her indoors (well I can dream)

Paul how much ballast will I need ?Having a day off tomorrow as the monthly shopping have to be done

[Paul TParticipant @pault84577]

Hi Mike

The calculated displacement is 65lbs and the ballast 50lbs but each model is different so the best method is to stick the model in the bath and fill it with weights until the correct level is achieved.

Paul

[mike farrellParticipant @mikefarrell21522]

Hi All I have a few photos of Thor in its skeletal state held by my wife which I hope to get on line when grandson comes home from Uni

Paul . Looked the suggested motors and found them doing the same revs, as Moxons I had found but at a lot less cost. Still important to me is to have a slow pulling Tug than a scooter racing about . Matching the ESPs will be important and any advice is welcome Thanks for now Michael

[Paul TParticipant @pault84577]

Hi Mike

The downside of buying motors from China is the lack of technical data or a proven track record.

As the motors are labelled as gearbox motors and operating at 24v I expect them to have plenty of grunt but how they perform when running for long periods (do they get hot or rattle themselves to bits) or even what the maximum amp load is would be a complete mystery until I got them on the bench and tested them.

After the testing I would know the build quality and the maximum amp draw from which I could specify the batteries and ESCs

They could work out to be fantastic tug motors but they could also be expensive scrap iron.

Paul

[mike farrellParticipant @mikefarrell21522]

Hi Paul ,re the motors running on 24 volts may be a small problem for me as I was intended running on 12 volt batteries as I have a fair few. In theory that should cut down the revs to about 2500 revs . .

I found a motor with 5 magnets and it stated it was a high torque motor running at 17000 rpm but as I often do I lost or forgot to save the page so will start afresh . Cutting the last of the 9mm ply tomorrow ,then will dry fit the lot and if it looks as good as I believe it will I will glue it up ready to skin it early next week

Would love to get it ready to take it to Haydock but I think the motors from China will take about a month so we,ll see Michael

[Paul TParticipant @pault84577]

Hi Mike

It is worth mentioning that if you wish to install the thrusters it is far easier to cut the holes in the pump base before gluing it into position.

Please forgive me for telling you 'how to suck eggs' but our hard of thinking member from Bushy Park might be glad of the information.

By connecting your 12v batteries in series you will have a 24v power supply.

Paul

[ashley needhamParticipant @ashleyneedham69188]

That Paul is so clever. I shall make notes.

Having seen the super dooper new props I would go for a pair of 2.5:1 geared 850`s on 12v as then you know what you are dealing with. Easy to watercool if reqd. . Although the props are 90mm in diameter, the blades are only on the outside bit and …well, Paul.. what is the effective blade area compared to say a normal 90mm 4 blade prop?? and having seen Trevors installation at the park in the corvette of a geared 850 it is a nice bit of kit

What sort of revs are you contemplating for these `normous twirlers?

Ashley

[mike farrellParticipant @mikefarrell21522]

Now then Paul I ,m not sure will fix 4 thrusters but question .What if I use 2 as water jets to rear as an extra power source without interfering with prop drive.daft question

[Paul TParticipant @pault84577]

R/Hon Sir Ashley Needham First Sea Lord of Bushey (sounds better than Mr Needham)

I expect the props effective operating range to be between 5000 to 10,000rpm, Theoretically the rotor type blades will produce and maintain an effective thrust across a far wider power band than traditional propellers: as applied to this particular model boat design.

The rotor design showed that the actual working part of the blade. i.e. where most thrust is produced, came from the outer 60% of the overall rotor length and that the inner40% added little or no extra thrust. The large 'dead water' area of the propeller boss actually increases performance.

R/Hon Sir Mike Farrell KBC & plug

Any extra push is always welcome but the two jets would have to operate outside the thrust area of the main propellers so that the wash from the thrusters didn't interfere with the water flow over the propellers.

I was trying to invent a mechanism to produce a rotating vector type thrust outlet for the model to enable the side thrusters to be turned either to the stern or bow and so increase the forward or astern power. I am ashamed to say that, as yet, I haven't been able to devise such a system.

Paul

[curlyParticipant @curly]

Hi Paul

In the army we had a piece of kit called the heavy ferry, we used to moved tanks across water with it. There where four drive motors one on each corner, they drove through the base of the hull. The drove through veins about 40 degrees, so thought if you put them on the thruster ports it will give you more movement, and extra speed. Hope this will help.

Dave

[Bob Abell 2Participant @bobabell2]

Paul

Got an idea for your nozzle predicament?

I assume the side thruster nozzles are squirting at right angles the the screws?

You could have a swivelling baffle that normally rests in line with the water flow

A servo could rotate the baffle through 45 deg each way and deflect the water jet…..Fore and Aft?…..ie….. A bit like a rudder action

No charge for this novel suggestion

Bob

[Paul TParticipant @pault84577]

Hi Curly

Thank you for the information and it is a big help.

You have reminded me about a programme I watched showing these amazing vehicles drive into a river and then join up to let a tank cross the river. It was like watching a ballet with 26t dancers and I remember thinking then how adaptable and powerful the drive units were.

Thank you again Curly as you have started me thinking again.

All the best

Bob

I have been playing around with a similar idea but couldn't turn the flow through 90deg (side thrust to astern / forward) the most I could achieve is 45deg which didn't work but now both you and Curly have set me thinking about vectors.

  

Paul

For the interested its a General Dynamics M3.

Edited By Paul T on 18/07/2014 19:28:41

[Bob Abell 2Participant @bobabell2]

Paul

The baffle/rudder could be a Becker rudder!……Now we're talking?

Bob

[Paul TParticipant @pault84577]

Bob

One of the problems is that I don't want the pieces of equipment to stick out more than 20mm from the hull sides, so they have to be flexible through 180deg.

Paul

[curlyParticipant @curly]

Hi Paul & Bob

The M3 was a later version of the old heavy ferry, it came many bits we needed a crane to build it. I'm long in the tooth. The vents moved 360 she could rely dance. The vents only were only about three ", so on a model I would say about 4mm. So I now leave it in the hands of the experts, sorry

Dave

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