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[oldiron]

A method I've used ,with success , to get alignment with a single Cardan coupling is to couple the motor as close as you can to the correct alignment. Connect the motor to a battery with an ammeter appropriately connected between the two. Start the motor and and adjust it's alignment until you have the minimum number of amps going to the motor. You'll here the noise level, amp draw decrease as you get closer to the proper alignment.

John

[oldiron]

Possibly....one of our more senior builders may take up challenge & offer comment to help us all....... .....Derek

 Derek
 Must have missed something, thought I'd already done that.

John

[derekwarner]

Guys.... I think my point has been missed.......

I am sure many senior members [not necessarily in years but in building experience]....could offer say ten liners on how to  

Consider the design......install the prop shaft.....install the engine mounting...."alignment".....bedding in the engine mounting....etc...

This may be too easy for experienced senior builders ....but the thought was for our newer or younger members.....Derek

[CF-FZG]

 I like the PVC and similar tubing for motor/shaft couplings for all the reasons given above. However, as boat modellers I could never understand why we use a single universal (Cardan) joint in our boats. We  think of universal  joints allowing for some degree of misalignment in between the driven and driving shafts, however with a single universal or Cardan joint we have to have the two shafts perfectly aligned. If we don't we get jogging in rotation, noise and the accompanying vibration. Getting shafts properly aligned in our small sizes can be quite difficult at times. When they are close enough aligned to prevent the noise and vibration, we may as well install a solid joint rather than a single Cardan coupling for all the good a single Cardan joint does.
  If we use a double Cardan joint separated by 90 degrees we end up with a constant velocity joint  and a for smoother quieter operation. We can have slight misalignment between shafts with no detrimental effects such as noise and vibration. The "rubber tubing" joints do this very well for our sizes. There are manufacturers of double Cardan joints, Graupner comes to mind, that do a far better than a single cardan joint.

John

John, I understand what you're saying about the 'double joints' which are soooo much better than a single U/J (of any size), due to the difficulty of setting, and maintaining, a single joint.

However, strictly speaking the joints are 'universal' and a Cardan is a shaft assembly with a U/J at each end - so you can't really have a 'single cardan joint'


Mark.

[Shipmate60]

There are several quite easy ways to align the motor to the shaft.
One of the simplest is to simply cut a length of brass tuning the same length as coupling and fit over the splines.
If you use this method you will need to cut a spiral in both ends.
This is so the tube can be a good tight fit and will not affect the alignment (eg droop) too much.
Do not let the motor hang on the tube but adjust your mounting till you get a good sliding fit.

Another way is to fit heat shrink around the universal joint and use as avove.
With a little patience it is not so terrible to get good alignment.

And lastly of course there is by good old eye and slow running.

One additional problem is that some of the coupling ends are not bored true so even lining up exactly CAN still lead to vibration.

The rubber tube type couplings can take misalignment and although will use additional friction, surprisingly little, and of course with no moving parts no noise.
These can still be aligned as above.

Bob

[oldiron]

Martin

 At Derek's worthwhile suggestion, I offer my name into the hat to do a write up on motor mounts and U joints in model boats if there's interest. It'll be along the same line as the air brushing tutorial I did.
 I'm due to give a talk on this subject at one of our upcoming boat club meetings, so I may as well do both.
 if interested let me know.

John

[RaaArtyGunner]

Guys.... I think my point has been missed.......

I am sure many senior members [not necessarily in years but in building experience]....could offer say ten liners on how to  

Consider the design......install the prop shaft.....install the engine mounting...."alignment".....bedding in the engine mounting....etc...

This may be too easy for experienced senior builders ....but the thought was for our newer or younger members.....Derek

as well as the less senior ones , that is, less experienced 

[RaaArtyGunner]

Old iron,

I am interested  you are never tooooooooooo old to learn

[derekwarner]

Thanks oldiron......... ....everyone 'sort of' thinks they know 'the best way' about couplings .....but thats why the subject keeps cropping up 

Now....an example.....if a new member asks.........how do I go about spraying my model?...........easy answer ...."just read the tutorial on the subject by oldiron".........

Derek

[Welsh Wizard]

One of the simplest of ways to align a shaft and motor is to get a various brass rods made up by someone with a lathe bored out to teh relevant shaft dia.
I have had some made up with 2mm/3mm/4mm/5mm dia the right length of a Huco coupling and never get a missalighned coupling.The more solid the coupling for alignment the better it is



Dave

[irishcarguy]

Thank you all, it is obvious that this is a topic that needs some more research & discussion from what I am reading here, so John I think it would be very good if you did just as you suggested. In the auto industry I have found on several occasions propshafts have been assembled wrong because the u/joints at either end were not aligned with each other & caused massive vibration. Usually we find it right after a customer installed their own u/joints(mechanics get it wrong too) What does surprise me is that no company has made a constant velocity joint which today are nearly universal in front wheel drive cars. Now there is a challenge for one of our interprising companies.The response to my question leaves me in no doubt that this is an ongoing problem & an area in modeling that could be greatly improved with some research. Not everybody in our hobby has the skill to make sure that drivetrains are in perfect alignment. My final thought is that the use of plastic tube in the joint is the safest bet for now. So once again thank you fellow forum members as always you all have been a great help to me & others reading this thread. Mick B. 

[oldiron]

  I'll start to put something together on the subject. Give me about a week to get prose and pictures together.

John

[Norseman]

Hi guys

As a newbie this alignment issue has been a big problem to think about pre restoration (fifties Hales Spraymaster). Just slowly turning the prop I could see a little movement at the unsecured motor. A friend has just made me a mount that has a little adjustment possible and is better layed out for my ex IC boat- so I really think I can do it now......... but I remain puzzled how one could tell the motor thru red moveable joint and on to the prop is perfectly aligned before I tighten everything up .............. after all the beeping red thing is loose and moves in a couple of planes at once and seemingly at will.

Yes please lads- a nice sticky lesson with the various options explained would be lovely for anyone new like me.

Regards Dave

[ZZ56]

I use the Dumas 'dogbone' connectors because they are easy to extend or shorten and they 'float', allowing the propshaft to slide under load without putting pressure on the motor.

[irishcarguy]

Thanks John, I will be glued to my computer & hanging on every word. I think it has been needed for a long time & it will benefit a lot of members. That is very kind of you to take the time. Mick B.

[RaaArtyGunner]

One of the simplest of ways to align a shaft and motor is to get a various brass rods made up by someone with a lathe bored out to teh relevant shaft dia.
I have had some made up with 2mm/3mm/4mm/5mm dia the right length of a Huco coupling and never get a missalighned coupling.The more solid the coupling for alignment the better it is



Dave

It follows logically, that if the shaft et all, are aligned as per the above and other similar methods, then why is it necessary to fit any type of "flexible/universal" type coupling, why not a direct rigid connection shaft to motor.
My understanding is a "flexible" coupling compensates for any miss alignment.

[Martin (Admin)]

"My understanding is a "flexible" coupling compensates for any miss alignment. "

Yes but also, allows for other separation of the shaft and motor... mind you a solid coupling would do that.

 Another thought is that the shaft and motor are mounted independently ( an uncommon datum? ) so  the
 coupling should compensate for this. Things like servos, drills, food mixers, internal combustion engines all share
 a common chassis that is internal to the construction of the machine, I don't think a boat's hull truly provides that.

There are a few motor mounts that do sort of do that, the Robbe & Graupner straight-to-shaft mounts and integral
 gear reduction drives.

 .... my science teacher, Mr Davies, was right, "Are you listening boy?"

   





 (  also see:  http://matthewsmodelmarine.wordpress.com/writings/all-geared-up/  )


 

[Nige52]

Although you would think that a solid brass coupling with grub screws is infallible, it's not.

I have a couple of these that have double grub screws, 2 at each end. I have found that if the motor shaft is not exactly the same diameter of the bored hole, when tightening the grub screws up onto the shaft, one will always tighten before the other, throwing the shaft off centre. it the same thing happens at the other end, but opposite, the 2 shafts end up well out of alignment and vibration is quite bad....

[roycv]

There is hope!

Hi all, I am just setting up a Huco coupling in a bare not completed hull.  Mine was noisy with vibration.  I tried everything, 2 sets of joints you name it, I have lots of spare inserts etc.

After a long morning I found the culprit.  The threaded coupling locked onto the prop shaft was slightly misaligned when the locking nut was tightened.

I put a washer between the lock nut and the coupling and carefully tightened up (counter turning nut and coupling), keeping it nice and 'square'.
I put the power on again and it just went silent!  Vibration and noise all gone.

Mind you I have to disconnect for painting and hope I can again get a nice free running connection.
Hope this helps, Roy

[Shipmate60]

Roy,
Did you use a "locking" washer or plain washer?

Bob

[roycv]

Hi Bob, just a plain washer a bit less than 1mm thickness.  So that it did not deform.
I have in a previous boat used a plain end with grub screw but it was a tight fit onto the shaft.  This worked OK.
regards Roy

[Shipmate60]

Just a thought Roy, might be worth a spot of locktite on the threads as the washer will reduce the effectiveness of the locking.

Bob

[roycv]

Hi Bob, thanks, I will do that on final assembly.
regards Roy

[RaaArtyGunner]

"My understanding is a "flexible" coupling compensates for any miss alignment. "

Yes but also, allows for other separation of the shaft and motor... mind you a solid coupling would do that.

 Another thought is that the shaft and motor are mounted independently ( an uncommon datum? ) so  the
 coupling should compensate for this. Things like servos, drills, food mixers, internal combustion engines all share
 a common chassis that is internal to the construction of the machine, I don't think a boat's hull truly provides that.

There are a few motor mounts that do sort of do that, the Robbe & Graupner straight-to-shaft mounts and integral
 gear reduction drives.

 .... my science teacher, Mr Davies, was right, "Are you listening boy?"



 (  also see:  http://matthewsmodelmarine.wordpress.com/writings/all-geared-up/  )


 

Martin,

Thank you  

[irishcarguy]

Hi all, I raised the issue on another thread last week as I noticed during some tests that the Huco couplings were very noisy, no they were not misaligned !. I am waiting for some bright engineer to design a C/V joint like we use on cars, or even some company with skilled designers should be able to do it . Any ideas anybody?.