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Author Topic: Universal & Flexible couplings  (Read 38260 times)

ACTion

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Universal & Flexible couplings
« on: November 17, 2011, 09:12:10 am »

A little local skirmish on another thread led me to research Huco couplings and I found some stuff on Farnell's website here. http://www.farnell.com/datasheets/529891.pdf. HUCO's own website has much more detail but I'm afraid that me and Newton.Metres don't agree at this hour of the day.
The implication is that those HUCO-Pol couplings much beloved by us boat mogglers are only rated up to 1000RPM! Our Aussie agent John Darke always recommends the use of the flexible jaw type with his geared motors. They are a lot more expensive but it makes you wonder how so many of us have got away with it for so long. I shall certainly think twice before using the 'plastic rattlers' again. There's always the flexible tube type made by our old friends Marks Model Bits.
I leave the floor to the cognoscenti for further debate.................
Dave M
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nick_75au

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Re: Flexible couplings
« Reply #1 on: November 17, 2011, 10:00:32 am »

Most of our models have low enough torque that the coupling can handle it, also commercial suppliers de-rate as the coupling could be used in a continuous duty application. At about 10000 RPM Ive had the "legs" that hold the spider fly apart releasing the spider.

Nick
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john s 2

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Re: Flexible couplings
« Reply #2 on: November 17, 2011, 01:13:18 pm »

Dave you are correct that it is not long before a Huco joint shows play in it. Sadly whatever plastic the joint is made of wears quickly. Why do i use them? Well its the range of inserts and the ease of fitting.Youre also correct that a lot of lads down my club run them at highish speeds.John.
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Martin [Admin]

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Re: Flexible couplings
« Reply #3 on: November 17, 2011, 04:23:39 pm »


In Hucos defence, I've not had a coupling go faulty or wear out that wasn't my fault.

 They used to do a range of white UJ with sort of alloy inserts that seemed higher grade components but I don't seem them around these days....
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6705russell

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Re: Flexible couplings
« Reply #4 on: November 17, 2011, 04:29:55 pm »

I always try and fit Mobile Marine ones with shear pins, good quality couplings.... :-))

Russ
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nhp651

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Re: Flexible couplings
« Reply #5 on: November 17, 2011, 06:53:15 pm »

A little local skirmish on another thread led me to research Huco couplings and I found some stuff on Farnell's website here. http://www.farnell.com/datasheets/529891.pdf. HUCO's own website has much more detail but I'm afraid that me and Newton.Metres don't agree at this hour of the day.
The implication is that those HUCO-Pol couplings much beloved by us boat mogglers are only rated up to 1000RPM!
I leave the floor to the cognoscenti for further debate.................
Dave M

glad you should mention that, Dave
The reason I made the constructive comment   was that I once had a Caldercraft PCF boat that I had built as a review model for (I think) Radio Control Boat Modeller and they were fitted with high revving big  torquey motors (similar these days to the torpedo 850) and was fitted with the couplings that Martin mentions. The white ones with alloy couplings. I had left the end shafts connecting to the couplings protruding some two-3inches from the Tubes for access to the motors under the deck, as the rear deck was fully closed for access/water tightness.................I only did one sailing run with it.and in my younger inexperienced days way back in the early 1980's...........yes, you guessed it....one coulping shattered under the high ( think about 6 -7000rpm,) and as it shattered, the shaft bent with the inertia at that speed with half a coupling still attached to it adding weight,almost at right angles, taking some of the prop tube with it and punched a hole through the grp hull.....I had to go into the lake at Fleetwood fully clothed to retrieve a very quickly sinking boat.I still hadn't got full photo coverage for the magazine article.
The electrics ( twin robbe 200 speed controllers at the time) plus futaba receiver where kaput with the salt water ingress into the hull and I learned from my experience.
Huco are not made for high speed motor transmission and the start up torque that a lot of motors give, especially if they are put under other stresses also.
Glad you brought it up  Dave, so that I could give my views in a calm and none biased manner. :-))

neil.
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ray123

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Re: Flexible couplings
« Reply #6 on: November 17, 2011, 08:42:12 pm »

i have used huco couplings & found them very good  however i now use the robbe  / graupner one's on all my boats now   they seem a better coupling :-))   

 i have seen on e bay metal couplings  any one else seen them or used them???  regards ray
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irishcarguy

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Help With U/Joints
« Reply #7 on: December 10, 2011, 08:02:11 am »

I have read conflicting reports on drive couplings. I will be running two Graupner 720BB motors with prop shop 55MM props.I am told that the Hugo( hope that is the right name) joints are noisy. I would like the best that I can afford & I don't want noise but I do want them to be reliable. I have NO experience with these joints, Help please, Mick B.
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Mick B.

Martin [Admin]

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Re: Help With U/Joints
« Reply #8 on: December 10, 2011, 08:12:34 am »

Hi irishcarguy,

 They shouldn't be noisy if you spend the time to align them... and align them perfectly.
 If you don't feel confident about achieving perfect alignment, use two couplings back to back, which creates
 a cardan type coupling like a prop shaft on a rear wheel drive car.
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barriew

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Re: Help With U/Joints
« Reply #9 on: December 10, 2011, 08:13:29 am »

I would agree that HUCO joints are noisy, even when the alignment is perfect. Both Marks Model Bits and Mobile Marine Models sell a joint which consists of two brass fittings joined by heavy duty hose - rubber or plastic depending on the duty required. These have no moving parts and so are quite silent.

Barrie
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Arrow5

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Re: Help With U/Joints
« Reply #10 on: December 10, 2011, 09:23:02 am »

I agree with Barrie , I replace the central part of the coupling with silicon tubing as used for exhaust pipe joiners on model glo engines. Make sure you have a size smaller than the splined parts of coupling.
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Chuffy

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Re: Help With U/Joints
« Reply #11 on: December 10, 2011, 09:55:59 am »

Can't agree more, changing all mine over to rubber fuel pipe, silent and with a little bit of give.

Paul.
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Circlip

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Re: Help With U/Joints
« Reply #12 on: December 10, 2011, 11:34:55 am »

Don't matter which coupling type you use, still not fully effective if drive and driven shafts are misaligned.

  Regards   Ian.
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Nige52

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Re: Help With U/Joints
« Reply #13 on: December 10, 2011, 11:43:39 am »

I've just checked my brass Huco couplings and the splines are about 7.9mm, so I take it that any tube with a 7mm ID will be ok to use? Only problem is I can only find silicone tubing with a 6mm ID....I'm just hoping it will stretch if I buy a length.. :embarrassed:
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derekwarner

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Re: Help With U/Joints
« Reply #14 on: December 10, 2011, 11:53:08 am »

I must agree with Circlip  O0

An engine to shaft alignment ...be it on a model ship or a full size vessel is the same

Today we have theodolite encrypted digital equipment to analyze the alignment & still get it wrong <*<
 
 >>:-( what happened to practical engineering of 50 or 150 years ago?

I could suggest the same applies to our model engineering today..... {-) Derek

 
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andyn

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Re: Help With U/Joints
« Reply #15 on: December 10, 2011, 12:34:55 pm »

Our couplings are free from any noise, and unlike Huco couplings don't put uneven strain on your motor and driveline, and won't break...

Andy :-)
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Marks Model Bits

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Re: Help With U/Joints
« Reply #16 on: December 10, 2011, 12:46:01 pm »

We have loads of 6mm ID silicone tube here. Ours stretches to 8.5mm no problems.......

Mark.
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daveorgan

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Re: Help With U/Joints
« Reply #17 on: December 10, 2011, 12:49:42 pm »

if you want something even more heavy duty use these there great.
http://www.modelboatbits.com/index.php?p=1_58
i use mmb ones there great never had a problem they dont slip there quiet highly recommend mmb couplings :-))
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Circlip

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Re: Help With U/Joints
« Reply #18 on: December 10, 2011, 12:51:02 pm »

Used one of the spline/PVC tube type couplings marketed by Rip-Max more than 50 years ago to fasten an ED Racer to a propshaft on the old Seaplane tender, - broke the propshaft due to whip  and that was at far less revs than some of todays Electric offerings. Another type was the Spring type, section of coiled spring  (like the Sillycone ones shown) between the shaft ends. Best one we found was the single ball and pin type. Never let us down, although it was correctly aligned.

  Yes DWD, what has happened to Muddle building and ingineering???

  Regards  Ian.

  Just seen the MMBtype offered, sorry, there must be a strain on the shafts if not aligned, basic mechanical properties.
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oldiron

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Re: Help With U/Joints
« Reply #19 on: December 10, 2011, 01:14:27 pm »

  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
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Circlip

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Re: Help With U/Joints
« Reply #20 on: December 10, 2011, 01:23:15 pm »

Don't forget John, cardens, either single or double, when used in industry usually have a sliding coupling (Car prop shaft) in the drive line.

  Regards  Ian.
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derekwarner

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Re: Help With U/Joints
« Reply #21 on: December 10, 2011, 01:33:31 pm »

Hi Circlip & all.......

This is not a simple or silly issue....... >>:-( <*<  "the installation of the prop shaft & alignment of the engine in our models"

My call is we don't need theodolite encrypted digital equipment  %%......but..... O0 we may use dial indicators  :o .......[a version of a dial indicator is the human eye  :-X]

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

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bobk

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Re: Help With U/Joints
« Reply #22 on: December 10, 2011, 01:35:32 pm »

I could never understand why we use a single universal (Cardan) joint in our boats.   John

I agree with that.  I used them on my first ship, and the transmission is noisy.  I used double ball  joint couplings in my destroyer and that is much quieter, which indicates that it is mechanically more efficient in compensating for minor missalignments, inevitable when using 2mm shafts despite using Plastruct tube to align the motor mountings before fixing down.  Even 0.1 mm out is 5% of the shaft diameter.  A single ball joint can only compensate for angle, not angle and axial missalignment.
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Circlip

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Re: Help With U/Joints
« Reply #23 on: December 10, 2011, 01:55:55 pm »

It is a simple issue Dereck, Lazyness and conveniance makes it complicated. Check how the old Flash steamers used to couple up.

   Regards   Ian.

  Edit. It's not a "Senior builders" problem, It's Mechanical Engineering.
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oldiron

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Re: Help With U/Joints
« Reply #24 on: December 10, 2011, 02:09:57 pm »

Don't forget John, cardens, either single or double, when used in industry usually have a sliding coupling (Car prop shaft) in the drive line.

  Regards  Ian.

 Quite right Ian, forgot to mention that.

John
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