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Prop turning stiffness and sound

(Hugh Somerset) #1

Hi, I have two T100 thrusters and I noticed that the stiffness when spinning the two props by hand is different, one also makes a louder almost rattling sound when turned on. In water one is also seems more powerful- Ive switched which ESC controls it so I’m sure its the thrusters.

I know the stiffness of rotation can be adjusted by opening up the thruster and adjusting the bushings. What stiffness and type of sound should I be expecting from the thrusters?


(Rusty) #2

Hi Hugh,

Some of the thrusters have a “clicking” noise caused by the tolerances of the bushings. We’re working hard to resolve that for future thrusters but unfortunately there’s not much you can do. It is usually much quieter in water because the water acts a lubricant in the bushing. If you think it’s a problem, email me and we’ll see what we can do.

As far as the stiffness goes, that’s definitely not normal and you should see equal thrust from both thrusters. If you’re comfortable doing so, could you take the stiff thruster apart and see if there is anything obviously wrong? If not, we’d be happy to have you ship it back and we’ll repair or replace it. We want to make sure everything works well for you!

Let me know.


(Hugh Somerset) #3

Thanks for the reply. I’ve played around with the motors and whats been making the ROV not move straight is using one clockwise and one anticlockwise propeller. Once I put identical propellers on both thrusters the ROV goes forwards perfectly. It seems strange that the props are the root of the problem.

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(Rusty) #4


That’s a very strange problem. What ROV and software are you using?


(Hugh Somerset) #5

We built our ROV and we’re using the basic ESCs that came with the thrustsers.

Last weekend we competed and won the Hong Kong Mate ROV regional contest using two T100 thrusters from the kickstarter. On the trial day however one of the plastic rings that sticks out the stator- does it count as a bushing? snapped off causing it to jam. We managed to take out the broken pieces and still use it sufficiently for the second day of competition but as a result the prop would wobble a lot. We really want to use these motors in the international competition at the end of June and were wondering how we could get that thruster repaired/ replaced.

We would also like to only feature blue robotics thrusters on our ROV by buying two more thrusters for vertical movement but we’re on a tight schedule for the comp, if we were to order one now could it be delivered within the next two weeks?


(Rusty) #6

Hi Hugh,

First of all, congratulations on winning the Hong Kong regional contest. That’s great!

I’m sorry you had trouble with the bushings! We are planning to change the adhesive used to install the bushings to eliminate that issues. It has happened once or twice during our long endurance testing as well. We’d be happy to replace the broken part on that thruster.

In terms of getting more thrusters, we are currently finishing a batch of T100s and we will be caught up with standard T100s. We should be able to ship within a week or so.

If you don’t mind, please send me an email (rusty@bluerobotics.com) after ordering to remind us to send replacement parts for your existing thruster as well.



(Harold Scadden) #7

Have you tried “staking” the bushings vice adhesive? I don’t know what the torque is like on the bushing from the motor shaft but if it is low enough, you could do this process vice adhesives etc.


(Hugh Somerset) #8

Cool we’ll make the order in the next couple of days. I’m not too sure that I was clear in my description of what’s snapped in the thruster as I dont see an easy way of fixing it. I’ve attached a picutreo of the problem.

(Rusty) #9


Okay. We’ll send a replacement for the whole “core” of the motor with plastic, stator, bearings.


(Hugh Somerset) #10

Perfect thanks, we’ve just made the order for two T100s and basic ESCs.

(Hugh Somerset) #11

Any idea how it managed to snap? We’ve been testing in an outdoor pool that’s quite dirty and we also found a it of hair around the outrunner.

(Rusty) #12


I definitely think the hair could have contributed if it was long enough to block the propeller or if it got tangled up. Similar damage was caused when we hit seagrass with our “SolarSurfer” and then ran the motor forward and backward repeatedly trying to clear it.


(Hugh Somerset) #13

All our gear has arrived, at looks great on the ROV. I can’t thank you guys enough for the replacement stator, obviously the thruster works as good as new now. I’m still not 100% sure how much turning friction there should be from the motor. I notice that of the four thrusters, when spun by hand, one of them clearly has much less turning friction than others and free spins a bit after letting go. I know this friction can be adjusted by playing around with the position of the bushing on the shaft. What is the ideal turning stiffness for the motors?


(Rusty) #14


Glad everything is working again. We we’re happy to help.

In terms of friction, less is obviously better, as long as the bushing is properly supporting the shaft and doesn’t allow too much room to move radially. The bearings are actually glued in place so I would not recommend trying to adjust them. Once they are wet, the water lubricates the bearings and the friction is reduced.