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[davejay]

Ok, another daft question!!


I'm building a Deans marine 1/24 BPBCo 71ft 6 in MGB77............just fitting the propshafts (one in at the mo, one to go!)..........question is that Deans recommends using two 'HUCO' type UJ couplings for each shaft joined by a splined joiner, does this make ensuring  perfect alignment less necessary, I've experimented having the motor a various angles and seeing whether it affects the smoothness of the drivetrain, it appears not to.


Any input/good advice gratefully appreciated.


Cheers, Dave

[Shipmate60]

I have found it easier and quieter if instead of the coupling silicone tube is pushed over the splines.
Much more forgiving about alignment too.


Bob

[Antipodes]

I have found it easier and quieter if instead of the coupling silicone tube is pushed over the splines.
Much more forgiving about alignment too.


Bob

Agree with this method. It's all I use now.

B

[oldiron]

for some reason model boaters only use one Cardan joint in their prop shafts. This doesn't make up a universal joint. Two Cardan joints phased correctly make up a proper universal joint. Would you put a drive shaft into you car with only one Cardan joint?  A Huco coupling is only one cardan joint by the way.
 If you use only one, the joint has to be precisley matched because there is no room for out of alignment with one cardan joint. This is why many model boaters get vibration and noise using this method.
A rubber tube is a quick simple way out.....to a point. If you are running a small size prop, you may get away with it. If you are running a large one, say what would be used on a 40" plus tug, it won't hold up.
A year or so ago, myself and Irishcarguy did a peice on "universal joints" the the whys and wherefores of them. You may find it benficial looking it up.
http://www.modelboatmayhem.co.uk/forum/index.php/topic,33847.0.html

John

[RAAArtyGunner]

John,
Digressing off thread, how is Irish guy ???

[oldiron]

John,
Digressing off thread, how is Irish guy ???

 I talked to him a few weeks ago on the phone. He was doing better than he was earlier in the summer. I'm not so sure his health is top notch though

John

[rnli12]

Hi,
 
I would use heavy duty rubber flexible couplings with the torque and speed you are likely to produce.
 
Rich

[irishcarguy]

Hi guys it is nice to know that you still remember me. Health wise I am doing O/K if I just keep from falling over. I have never had good balance but it sure has got worse over the last 18 months. I read the forum posts every day without fail unless I am not well. I have a very good doctor & has given me great care he even comes to the house to check up on me & phones me most weeks as well. I met him when I built a very special motor for his M.G.B. he just can't get over how much power it now has. He bought a used Rover v8 motor with the idea of fitting it in the M.G.(after I rebuilt it with him )but now he has second thoughts  he is so happy with how it goes now. I called him one night feeling very ill & he said from the symptoms I had  a very bad case of pneumonia that I would be dead in 36 hours without the pills & got me antibiotics within an hour & brought them to my house @ 12 pm. Now my fear is losing him. He has given me both his home & cell phone #s as well.  I am still trying to finish my boats & have built a small workshop in the back yard to put my lathe (Chinese) & my mill (Chinese too) in it, they are at present in my workshop 12KM west from here. It will make things easier for me. I already have most tools I need at home (too much) I see the question of U/Joints still comes up. I have found in my ramblings at the model shops there is a new front wheel drive axle made by Traxxas that is a work of art & could be converted for boat use easily, it is a proper C/V joint & is about $30.00 dollars Canadian. I will convert one & try to get a picture up on the Forum ( Neil said if I send him pictures he will do it for me,) very kind of him & it is nice to see him back( Thank you Martin)I will rap up for now & thanks again for the concern, John is a great guy. Cheers from Mick B in CANADA.

[Shipmate60]

Sorry John but I have found the thick walled silicon tube stronger than the thin plastic couplings.
If you keep the tube short it is incredibly strong and tightens as the loading increases.
I have never had a failure using this method but have destroyed several plastic couplings.


Bob


PS Welcome back Mick, hope you are well, yes you are well remembered.

[RAAArtyGunner]

 

[Tug-Kenny RIP]

So nice to hear from you Mick.  Your contributions when you can, are most welcome.

When does the Snow season start where you are ?  I lived in Ontario many, many years ago and thought the snow a novelty until I went out in it by foot.  Never again !

Stay cosy

regards

ken

[chas]

I too use silicon tube couplings. And agree that they are strong, reliable and quiet. I went over to them after Hugo style couplings failed. I use them on 380, 540,550 size motors, direct  and geared drives. One model has a 60 mm prop and has been fine for 3 years.
The importance of accurate lining up of motor and shaft is hard to overstate, I always get the best alignment I can.
Chas.

[oldiron]

So nice to hear from you Mick.  Your contributions when you can, are most welcome.

When does the Snow season start where you are ?  I lived in Ontario many, many years ago and thought the snow a novelty until I went out in it by foot.  Never again !

Stay cosy

regards

ken

Thanks Kenny. I've got a kit  Irishcarguy couldn't finish.. The Imara, I promised him I'd finish it and post the thread on here. so you'll see me back.
The four letter word  "SNOW", yuk. Could be back any time from the end of October. That said, its going to -3C tomorrow night. We'll see what happens.

John

[oldiron]

I too use silicon tube couplings. And agree that they are strong, reliable and quiet. I went over to them after Hugo style couplings failed. I use them on 380, 540,550 size motors, direct  and geared drives. One model has a 60 mm prop and has been fine for 3 years.
The importance of accurate lining up of motor and shaft is hard to overstate, I always get the best alignment I can.
Chas.

Glad you've had  good sucess. A proper U joint is there to take misalignment, intended or other wise. Here again, I go back to car , or any other vehicle, drive shaft (either front wheel  or rear wheel.. Porperly done, they are designed to take misalignment.
John

[grendel]

Having just gone through this, the Huco joints are fine if you are only having low revs, I was running one through a 2.5:1 reduction gearbox and it was fine, as soon as I needed to remove the gearbox and it was turning at 11,000 revs the coupling was screaming - even in perfect alignment. so I swapped over to silicon rubber tubing and its been fine. dont heavily grease the prop shaft, the motor slows down and gets hot. suffice to say I now have a bigger motor on my model and its finally performing as I want it to.

[oldiron]

A single Cardan joint, Huco or other wise can be a great frictional drain on a drive system as well as producing noise and vibration. Granted  a rubber (call it what you will) tube will do for smaller props (the tug in my head picture runs a 94 mm prop), I doubt if a rubber tube would last long. This is where you need the strength of a double Cardan joint.
Since the question, initially was about Huco joints, the solution to them is , as I've mentioned before, a double, phased Cardan joint. If they are not double and not phased, they are a total aggrevation. Done properly, which model boaters seldom do, they are an absolute pain. Why not do them right?

John

[Shipmate60]

John,
Once again I will take exception to your theory on Huco couplings versus thick-walled silicone tubing.
From an engineering point of view the Huco coupling is not made for large props or high speed.
The defining strength is in the rivet through the thin plastic body.
When placed under high loads or speed either the rivet or the plastic where it is thinned to allow the joint to move.
With the silicone tube you can ensure that the coupling ends are aligned and within a few mm of each other. this ensures that "kinking" is impossible and as the forces increase the tube tightens on the coupling end.
I my years of experience using both these methods I have had several Huco failures on high speed and large props bun so far have never had a tubing failure using the splined end and a suitable size inside diameter and at least 3mm walled tube.


Bob

[oldiron]

John,
Once again I will take exception to your theory on Huco couplings versus thick-walled silicone tubing.
From an engineering point of view the Huco coupling is not made for large props or high speed.
The defining strength is in the rivet through the thin plastic body.
When placed under high loads or speed either the rivet or the plastic where it is thinned to allow the joint to move.
With the silicone tube you can ensure that the coupling ends are aligned and within a few mm of each other. this ensures that "kinking" is impossible and as the forces increase the tube tightens on the coupling end.
I my years of experience using both these methods I have had several Huco failures on high speed and large props bun so far have never had a tubing failure using the splined end and a suitable size inside diameter and at least 3mm walled tube.


Bob

My point is from the start, , whether they be Huco or some other Cardan style coupling, from an engineering a=standpoint model boaters don't use Cardan joints correctly. They expect one joint, no matter what the manufacturer to make a proper universal joint. Like you. I've had years of experience on U joints, both from an indutrial stand point and a model aspect, and you can't use a single Cardan jopint and expect it to operate as a universal. Propely used Cardan joints don't need the shafts closely aligned, thats why they are used.

John

[chas]

Hi John, in your example of a car etc, the ujs are there to cope with designed in or expected misalignment. They are a necessary part of the design. In a correctly installed model boat installation, there should be no or next to no misalignment. The coupling is just a coupling, and the smoother and quieter it runs the better. Silicon tube does just that, and if I ever need to use a larger prop than the 60 mm I've used so far I will have no hesitation in continuing with what I consider a strong and proven method.
Chas.

[oldiron]

Hi John, in your example of a car etc, the ujs are there to cope with designed in or expected misalignment. They are a necessary part of the design. In a correctly installed model boat installation, there should be no or next to no misalignment. The coupling is just a coupling, and the smoother and quieter it runs the better. Silicon tube does just that, and if I ever need to use a larger prop than the 60 mm I've used so far I will have no hesitation in continuing with what I consider a strong and proven method.
Chas.

no one said you had to change, Don't take it personal.
But engineering is engineering no matter what the size relative to Cardan style joints.

John

[chas]

No problem John, I have the utmost respect for your view. I just prefer another method. It's all part of the fun of modeling.
 My whole point was that the need for a good uj shouldn't normally arise .
Chas

[Shipmate60]

John,
From an engineering point of view there are several types of marine cardan shaft that do use bonded rubber interior parts so in full size engineering we could BOTH be correct.


Bob
retired Sea Going Marine Engineer.
Not boasting just letting you know I am  Marine Engineer.

[oldiron]

John,
From an engineering point of view there are several types of marine cardan shaft that do use bonded rubber interior parts so in full size engineering we could BOTH be correct.


Bob
retired Sea Going Marine Engineer.
Not boasting just letting you know I am  Marine Engineer.

 
Now that we have the chest waving out of the way, can we get back to the first question that started this list for the poor chap that has probably run off by now.

 I think the poor lad has got the picture by now

John

Not boasting but stationary engineer and marine engineer and nuclear engineer

[Colin Bishop]

Personally I don't favour direct drive. I have always preferred pulley drive. It makes alignment a doddle and has the great advantage of enabling you to gear down the motor to the prop which enables both to run much nearer to their optimum efficiency. What's not to like?

Colin

[Bob K]

I agree, this is getting silly.  The unfortunate chap only asked a reasonable question.

In my experience, no matter how accurately you try to align model boat motors and their shafts, there will always be a very small misalignment in 1 to 3 planes.  Stiff foam rubber around the clamped motor helps, but you should always plan to fit a coupling.  A single joint is better than nothing, but double is theoretically ideal.
What type you use it up to you, all have advantages and disadvantages.