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Azimuth mount for the T100 / T200 series


(Deckie) #1

Like many of you, I have a few thrusters on order, in this case a pair of T200’s for a large scale 1:27 RC model of a Damen 2310 ASD tug. Make no mistake, this model is being built for towing and bollard-pull comps at clubs throughout Australia.

I needed a high (perhaps these will qualify as stupidly high, given the application) power density drive in a small package and these fit the bill, with a definite plus in the inherent water cooling of the design. Needless to say, I had to become a kickstarter backer as soon as I saw them!

However I’m still not sure on whether to bother with fitting blue esc’s as the same quantity of slip-ring contractors will be required in each mount either way.

In order to do so, custom DIY azimuth mounts will need to be made for these units, and once they arrive early next year, you’ll find an account of the trials and tribulations i’ll be going through here along with any drawings/ CAD files, etc. If successful, it’d be nice to see these showing up on other models, even USV’s??? :smiley:

damendsasd-tug2310yn-512904tancred20120806 (1.11 MB)


Mission Planner Rover model skid steer vs differential steer?
Suitable servo for rotating T200
(Rusty) #2

Hi Deckie,

Welcome to the forums and thanks for sharing your project. Sounds really fun! I think two T200s will be a lot of thrust for a 1:27 scale tug.

I think an azimuth mount is very useful for a variety of applications. Are you planning to have continuous 360 degree rotation capability with the slip ring? The thrusters can run in reverse - have you considered using 180 degree rotation combined with forward and reverse thrust to provide thrust in any direction?

Please share your progress once you start working on the mounts! Excited to see it.

Best,

Rusty


(Deckie) #3

It’s going to be a hell of a challenge!


(Deckie) #4

Rusty,

Yes the intention is for continuous 360 degree azimuthing and only forward throttle like the real thing. Running forward only escs allows max thrust at all azimuth angles as well (we already would lose a pound or two of thrust running the thrusters in reverse).

Electronic and hardware components required are as follow:
Quadrature encoder with zero point.
Arduino Uno.
H-bridge Shield
Small geared 12 volt dc motor as actuator.
3 gears of identical size and pitch.

The Arduino would be required to translate/mix the RC TX’s joystick x and y axis’ into rotation angle for the thrusters and throttle pwm signals for the esc.

Other components such as the thruster shaft to be determined during design and dependent on how the mount will be built (built-up or cast?, built-in or external slip ring?, etc).

Another member is sending me an image of the design he has come up with, ill let him introduce that himself.

As for the thrust to scale ratio, well better too much than not enough, besides thats what we have throttles for :slight_smile:


(Rusty) #5

Deckie,

Sounds like you have it all figured out. I would recommend Pololu’s geared motors with quadrature encoders but they don’t have a zero point so it would be difficult to use. I built an actuator with those once and it had to be re-centered every time it was powered on.

I’d love to see the other member’s design.

Keep us updated.

-Rusty


(Deckie) #6

G’day Rusty.

Thanks for pointing those out! it’d be an easy fix with a hall effect sensor and perhaps a metal servo arm set to the Zero Point at the top of the shaft.

The biggest problem (and potential killer) with the whole project remains the slip-rings. Within the physical dimensions required and the current handling required, only the expensive ones can compete and there are only a few…


(Deckie) #7

Check this out:

 

http://forums.parallax.com/showthread.php/141590-Slip-Rings

 

The sneaky low-cost option might be good quality, 3 - pole, right angle guitar jacks and sockets like these:

 

The guy in the thread reckons they work alright at 30 amps with a slight temperature rise. Not sure how a brushless ESC will go commutating through them though…



(Spally) #8

Deckie,

I am woking on vector mounts myself. Below are a screenshot of my design so far. Needs some tweaking but I want to get a 3d printed version to see how it goes.

 



(Spally) #9

And a couple more…




(Deckie) #10

I’d definitely be printing and trying a prototype if I were you. I can see where I’d mount a slip ring at the top or a diy audio jack solution… The only change i’d make would be a small Teardrop platform perpendicular to the Vertical axis of the mount, near the top just under the flange. I’d through mount the gearmotor with encoder in an underslung fashion to it. It also provides a mount point for the zeroing sensor.

ABS, High-impact Nylon or Acetal are all good choices for this. What software are you using for designing by the way?


(Deckie) #11

You could also try Shapeways for the printing.


(Rusty) #12

@Deckie - Very cool find with the audio jack. That seems like it could work really well. I assume the slip ring will be mounted inside the enclosure so that it doesn’t get wet?

@Spally - Looks like you’ve got a good start on a design. We’ve used Shapeways and Sculpteo with lots of success and you get very high resolution models for a good price.


(Spally) #13

Rusty & Deckie,

I will check out Shapeways and see how much it will cost to print. What I need to determine is how much clearance I need between the moving parts. Currently it is 0.2mm between the tubes and 1mm vertical play in the tubes. I have designed it so that the tubes can be lengthened to ensue the top is above the waterline to prevent water ingress. I am also looking at fitting 2 rubber rings and a capped hole where marine grease could be pumped into it but I will have to see how the current design works.

I have changed the bottom where it mounts to the thruster to mirror the T100 top with an extension at the front for the power cable hole. This also allows easy extension to adjust the depth off the hull without adding a lot of drag. I will post some picks tomorrow.

@Deckie, it would be easy to add any mount designs for your slip rings. Until last week, I had never used Autocad for 3D work. Wouldn’t have got anywhere without Google :slight_smile: Now I am confident in creating any shape you need.

@Rusty, any thought of integrating the power cable in the front vertical support rather than being exposed?


(Spally) #14

New design. Needs a couple of tweaks.




(Rusty) #15

Looking good, Spally! Is there a motor inside yet?


(Spally) #16

I install the 2 T100s onto my test boat tomorow for speed test. I am getting quotes now to print 2 of my mounts so I should have them tested in a few weeks. I even thought about leaving the 2 BTD150 units and mounting the 2 T100 opposite for a “Thrust Off”. No real reason, just cause I can!

Since I am running a pair, I will be using one high torque servo between them to do the steering. If you look at the top image, you can see that 2 holes are not countersunk, ready for a ball joint. I can get over 70deg either side of centre which is more than enough for my use case. As for Deckie, if he sends me a sketch of how he wants to arrange it, I will see what I can do. (I work for Beer!)


(Deckie) #17

Could I grab the dimensions for the top flange/mount? You’ll be getting a .3ds file via email.

I’ve got two main options. Both use a metal ring bolted to the top flange with teeth on either the inner or outer diameter, hence an internally or externally mounted azimuthing motor. Its drive gear would ideally have the same diameter, pitch and teeth count as the ring on the top flange, will help simplify the code.

Regarding your setup, as Rusty pointed out earlier you can get 180 degree servo’s. Top work so far too mate!


(Spally) #18

Deckie,

Inner Tube Radius: Internal 19mm External 24.8mm

Inner Tube Cap Radius: Internal 16.9mm External 30mm

Mount Tube Radius: Internal 25mm External 30mm Outer Flange 40mm

Mounting the T100 centrally means that a minimum internal dia of 38mm is required to allow access to the rear mounting screw. If you mounted the T100 such that the center line is in line with the screws, you could reduce that down to the mid 20’s. Just got to give yourself the screwdriver clearance.

I have been working on a Servo Mount. I cam up with this design. It Key fits onto the Mount tube and is captured with a newer wider Inner Tube Cap. Simple, no screws, can be moved around to help fitting in difficult installations. If I needed to, I could just print a mirror image of the Servo Mount and it will still fit.

Got a quote back from one firm, over $600! See what the others come back with…




(Rusty) #19

Spally,

$600 seems steep for Sculpteo or Shapeways, but in line with what I’ve seen from other companies. I would recommend reducing wall thickness if you can to reduce cost. I generally use wall thickness between 2-3mm and the parts are pretty strong.

-Rusty


(Spally) #20

Rusty,

I have submitted a job with 3D Hubs and got a price of $260 for 2 complete sets. I have thought about reducing wall thickness but I still need to allow for the screws. Maybe I could reduce the thickness in the middle sections or even make them hollow where possible. These are to be mounted to boats for Bathymetric Surveys and will have 20kg of equipment in it so I want to ensure that they will withstand that weight if placed on the ground. The overall height could be modified easily for other installations but I need to ensure that the top of the mount is significantly above the waterline. I saved a significant amount changing to these over the BTD150’s plus I don’t need to purchase rudders which saves me again.

Hopefully have the sets by this weekend.