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[tonyH]

Upstairs Garage? Exactly how did you word the planning application?

[raflaunches]

Upstairs Garage? Exactly how did you word the planning application?

    You can see why it’s taken so long!
Should be an upstairs flat above the garage for my sister. She gets to live upstairs and we get to play in the garage beneath but as you can imagine that a lot of work was needed to fireproof and separate everything.
At least we get to play with the boats again 

[ballastanksian]

Yay for playing with boats again!!!!! I saw a period image (on this forum IIRC) showing the skeleton of a ship's rudder and being amazed at the complexity of castings and rivetted plating, and this is before you get to the plates that form the actual rudder skin!


Looking fab Nick.

[raflaunches]

Hi Ian


Many thanks- she is coming along nicely once again. Yay for playtime
The rudder has been filed and filled to fit and will have a final sand to smooth it completely tomorrow. The motors on the other hand are being a bit of nightmare at the moment especially the outers. Luckily the double coupling allows it to run smoothly in this position but it’s not 100% ideal. The joys of narrow hulls and large-ish motors!
Hopefully more tomorrow.

[Colin Bishop]

That looks really painful Nick!

Colin

[raflaunches]

Hi Colin


Yes it’s been a bit of pain in the preverbal behind! Might have to carefully reduce the length of the inner shaft tubes to move them further aft in the hull to give greater clearance for the outer motors. Due to the time passed since we initially planned this area we have forgotten or not remembered how we planned to do them.

[mrlownotes]

Hi Nick, can you increase the length of the coupling to allow the outer motor to just slip in behind the inner motor ?

[raflaunches]

Hi Alan


Possibly, I’ll have a look tomorrow morning to see how if any thing can be added.
Happy New Year by the way to you

[mrlownotes]

Hi Alan


Possibly, I’ll have a look tomorrow morning to see how if any thing can be added.
Happy New Year by the way to you

Happy New Year to you too Nick

[Geoff]

Hmm, what happened to the earlier set up as the motors seemed to fit okay. I would counsel you shorten the inner shafts so you can move the inner motors aft so you get a much better fit for the outer motors or alternatively move the outer motors forward even if it means cutting a hole in another bulkhead. You can always construct a waterproof box around the rear of the motors so there is room. The hull will easily be strong enough to take this kind of modification.


Whilst the couplings will work with the current level of misalignment it will put a great strain on the couplings which will at some point fail and in any case will cause vibration.


Nice to see the progress!


Cheers


Geoff

[Geoff]

Nick, as an alternative could you move the outer engines forwards into the next section and use a lay shaft with a coupling at each end as this would solve the alignment issue. I'm thinking you probably have room to do this!! 


Cheers


Geoff

[Akira]

I have had issues similar to this before. I solved them by taking a dogbone, in this case a Dumas nylon one, cutting it in half and inserting each half into a piece of brass tubing to fit. I think it was 3/16 id. I cross drilled thru the tubing and the dogbone  half and oined the dogbone into place with a brass micro screw, although just piece of brass rod would work as well. The nice thing about this rig is that you can make the jack shaft as long or short as you want, as long as it in not shorter than the original dogbone.
Just a thought.

[raflaunches]

Hi everyone


Sometimes work just stops play so Dad has been correcting the problem over the last few evenings.
When we trial fitted the motors in August/Sept the prop shaft tubes were not permanently fitted to the hull but when he came to fit them permanently in November he accidentally glued them so the motor ends were all level when they should be staggered. So to correct this the inner shaft has been reduced in length by approximately 1 inch allowing the inner motor to move aft and the outer motor to move inboard straightening both couplings.
On another good note: the Glorious now has her props from Prop Shop- a pair of 1415 LH and RH 3 bladed items fit beautifully as per the original vessel. They should propel this model very well especially with four motors.

[Akira]

Another way to skin the cat! Poor cat. I am glad it worked out for you. Simon's wheels look wonderful, of course!

[GG]

Raflaunches,
              I see you solved your motor placement problems with the use of couplings to cope with the misalignment of the shafts.  You, and possibly others, might find it interesting that, provided the shafts are in the same plane (doesn't matter if the plane is vertical, horizontal or anything in-between), the couplings we use in this hobby can accommodate surprisingly large angles with little power loss.


Having long striven to keep motor and prop shafts perfectly aligned, it seemed worthwhile to see just what angular misalignment could you get away with.  So a little experiment was undertaken to fill the Covid enforced free time.


Much to my surprise the single Universal (Carden/Hooke type) did not seem significantly distressed by angles up 10 degrees. This was similar to a coupling made up from some silicone tubing about 11 mm O/D.

The other couplings (Double Universal,Ball and Socket, Dog Bone and 8 mm O/D silicone tubing) could accept double this angle.  In fact the "Ball and Socket" and "Dog Bone" types did not seem to be aware of any misalignment at all.

Not an exhaustive experiment and, as said earlier, the two shafts were in the same plane.  But, it does suggest that my previous obsession with getting both motor and prop shafts perfectly aligned could have been misplaced?

A fully detailed article was sent to the magazine Model Boats several months ago, so I will not elaborate any further.
Glynn Guest [size=78%]    [/size]

[Colin Bishop]

Handy video animation here showing relative motions and why a single joint is not constant velocity but a double one is.

Even I could understand it. 

https://www.youtube.com/watch?v=LCMZz6YhbOQ

Colin

[Geoff]

How very interesting! I suspect that if the angle is slight then there will be very little practical difference but if a significant angle the output shaft will be rotating at different speeds depending on its point in the curve/motion but in aggregate will probably be very close to the input shaft, unless I'm reading this wrong but what a fascinating take on this topic.


Cheers


Geoff

[Colin Bishop]

Yes, at significant angles you could get propeller oscillation - would that have an effect on the motor or ESC?

I was just wondering if it puts sress on some of the bearing surfaces leading to uneven wear.

Colin

[GG]

Re my previous post on coupling test.
I must confess although knowing about this possible problem with simple couplings, I have never experienced them in practice.


This might be due to my preference for "loose" rather then "tight" couplings.  Some Universal types have been so stiff when first bought that they might have well been rigid couplings. If they could not be freed-up with a running in session then I'll admit to opening up the holes slightly'.


Simple motor-prop shaft coupling made with silicone tubing would only suffer from some hysteresis losses from the repeated bending/unbending cycles along with some frictional losses from side loading at the bearings I guess?


It still seems the best idea to get motor and prop shafts in line, but I refuse to loose any sleep if my next model demands a modest angular mismatch, provided the shafts are at least in the same plane!


Glynn Guest

[Baldrick]

  I guess the big problem with the single flexible joint is that it is creating harmonic impulses into the prop shaft when at an angle and not straight . Depending on certain other factors such as the shape of the hull and stiffness of the shaft mountings their is the likelihood of generating all sorts of vibration and noise.

[BrianB6]

I think one of unmentioned problems is current draw by the motor.  I always put an ammeter in circuit when aligning a motor. It is amazing how little variation in angle can increase the load.

[dodes]

As everyone is talking about flexible couplings, myself gave up mechanical couplings some time ago because of noise etc and went over to rubber hose couplings and have not looked back since. They can accept some misalignments and they do take out some of the stress caused by overloading when as some do full speed one way and then full the next way, which technically can only be done on steam recip engines.

[Akira]

Excellant video Colin. Thank you for posting it. It explains where a lot of folks vibrations come from.

[raflaunches]

Hi everyone and especially Ballastankian who wanted to know this process that my Dad uses for inside his hulls.
I’ve included some pictures of using PVA (Wood glue) method but it takes a while to do and we still paint over the top of it anyway.
In areas that have large gaps we paint on PVA to fill the gaps and seal the area. We usually run it around the frames to skin plates much in similar way that you’d seal up a shower tray.
Using the paint method we use oil based household paint by Dulex. It can be thinned slightly with white spirit to allow the paint to seep into the wood grain. You will need to apply several layers to build up until you get a solid coat of paint. The final picture shows that there was a small hole in the hull that wasn’t 100% visible but the thinned paint seeped through and sealed the gap internally. The outside of this hull will be painted with a resin and sanded flat so I can paint with spray rattle cans and airbrushes.

[ballastanksian]

Super dooper chaps! Do say thanks to Steve for me Nick. I recall his description, but there's nowt like some snaps to give the eye-brain coordination something to latch onto.


I assume Steve uses whatever Oil based household paint he has to hand as long as there is enough to do the job reliably?