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Author Topic: True C/V joint.for our boats  (Read 17088 times)

oldiron

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Re: True C/V joint.for our boats
« Reply #75 on: March 13, 2013, 12:04:42 PM »

I like this hex idea you lot got going on. If you make the coupling oldiron post it on here. The only thing that would concern me about it being brass is that the hex might round off.

  If the fit between the inner and socket was sloppy, I agree, in time, it would round off. However, I think you'd be fine if you had a proper fit with no slop. Don't forget, there are six surfaces applying pressure during operation.

John
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w3bby

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Re: True C/V joint.for our boats
« Reply #76 on: March 13, 2013, 12:29:15 PM »

Too large maybe for you guys but from Ian's Boats, 7 -5mm or M8-5mm

Norseman

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Re: True C/V joint.for our boats
« Reply #77 on: March 13, 2013, 03:03:36 PM »

Hi guys
I'm following this thread with interest, and it's great to see people coming up with ideas. I have a question about the last few suggestions .... I think what got Mick started was the noisiness of his original set up - so are the last few suggestions as quiet as you would expect Micks joint to be?

Dave
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RMH

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Re: True C/V joint.for our boats
« Reply #78 on: March 13, 2013, 03:31:02 PM »

I quite like the idea of the Dumas dogbones but having had a trawl around the usual traders no one seems to sell anything like them in the UK
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Mad_Mike

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Re: True C/V joint.for our boats
« Reply #79 on: March 13, 2013, 03:31:02 PM »

  If the fit between the inner and socket was sloppy, I agree, in time, it would round off. However, I think you'd be fine if you had a proper fit with no slop. Don't forget, there are six surfaces applying pressure during operation.

John
yes that are 6 surfaces, and closer it is to being a circle. the more flats the more round it is. the more round it is the better its good for rounding off. It would be better if it was square or even triangle but then i dont think it would flex. It remind me of torx bits and screws from when i was a garage apprentive. I generally do not agree as whole that the more surfaces there are the better application of pressure. Especially torx bits, all you got to do is get a bit of rust in a torx screw use the bit and next thing you know your drilling the screw out because the teeth have crumbled.
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grendel

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Re: True C/V joint.for our boats
« Reply #80 on: March 13, 2013, 04:00:58 PM »

torx screws and bits - theres your splined drive.
Grendel
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Re: True C/V joint.for our boats
« Reply #81 on: March 13, 2013, 05:11:21 PM »

I think there are more ways than any of us can think of for making joints. I would point out here the C/V joint has been around for a long time & since the advent of the Mini in 1959 they have been the go to joint in various forms, & we should ask ourselves why. I like many of tha ideas discussed here, but for $20.00 & about 1/2 an hour of my time I can have a true C/V joint that will adapt to most motors & shafts & I am sure has been well tested in competition by its makers who are one of the leading companies in the model car racing business & are very successful at it. I can see good & bad in the hex drive for instance, you are assuming that the head of a nut or bolt is a true hex. Those of us that use nuts & bolts everyday of our lives are well aware that is not the case. Can you imagine a drive made from an Allen screw turning @ 6000rpm and does not run true. In the case of my own prototype it was only out about 3 degrees and the vibration was bad,putting it mildly. The Dumas dog bone seems like  good bet of all the ones you guys have discussed, but until something better than the HPI racing unit comes along, guess what will be fitted to my boats, Mick B.
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Mick B.

irishcarguy

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Re: True C/V joint.for our boats
« Reply #82 on: March 13, 2013, 05:18:22 PM »

One other point I would like to make, as long as we accept the joints that are been sold to us now nothing will change,it is up to us to put pressure on the retailers & the makers of this poor quality stuff to improve what they are selling, if not done let them keep them. Mick B.
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Mick B.

oldiron

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Re: True C/V joint.for our boats
« Reply #83 on: March 14, 2013, 04:09:47 PM »

Mick

  I totaly agree with your last entries, especially where it behoves us to press manufacturers for better quality universals. however, we have to realize there's a problem first.   
  Not to steal your argument, but I took one of the ideas/suggestions made by a previous contributor on this thread and made up a U joint using a socket and bolt arrangement. the cost came in at about $12 Cdn. As to the vibration concern. I have yet to try it under load. This is a build and try it exercise. We'll see where it goes. For the minute I'll show where I've gone with it.
  I selected two hex head bolts at my local hardware store (Canadian Tire for you Canucks), plus two 1/4" drive sockets to fit the bolts. I turned the square drive end off the sockets. This leaves enough round inside the socket to grip the prop/motor shaft. I drill out the round opening in the socket to an even 1/4". I then turned up a short length of brass that press fit into the 1/4" hole inside the socket. I then drilled and tapped the socket for a 6-32 grub screw to hold the unit to the motor shaft. The brass filer was drilled to be a good fit on the motor shaft.
 For the dog bone, I took the two hex head bolts and made a sleeve to connect them back to back (see photo). Each end fits inside each socket. There is tons of end play for those worried about that. These can be made in any size you want. They're not likely to round off under our usage. The only question remains, when the ice is off the water, what they're like for vibration under load.
  This was an hours work engineering and building this morning for a very cheap sum.

John
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irishcarguy

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Re: True C/V joint.for our boats
« Reply #84 on: March 14, 2013, 04:31:09 PM »

It will be interesting to see how it works John,glad to see you bought the good Canadian Tire sockets, I use a lot of their bits & pieces, cant beat them for price either. There are other solutions but the quality of the HPI joint & price makes it a no brainer for me. I must learn how to post photos, a picture is worth a thousand words. Mick B...
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vnkiwi

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Re: True C/V joint.for our boats
« Reply #85 on: March 14, 2013, 05:22:43 PM »

nice one - keep up the good work.
inerested in how it reforms
cheers
vnkiwi

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oldiron

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Re: True C/V joint.for our boats
« Reply #86 on: March 14, 2013, 06:59:46 PM »

Well lads, I just tried out my U joint described above. As much as I can test it on the bench it passed in flying colours. There was no discernable vibration no matter what angle I placed the motor relative to the prop shaft (within the limits of the dog bone of course.)
The only noise was from the gear box in the Decaperm motor. As i said, this unit can be made to any size desired at minimum cost.
  The boat its installed in is the Joffre I'm building for another thread.
   The bottom picture shows the motor in operation.

John
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vnkiwi

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Re: True C/V joint.for our boats
« Reply #87 on: March 14, 2013, 07:17:28 PM »

That's cool. Will have a go at one of these, but could be interesting without a lathe.
Mick, we now need to see yours in a boat and trialed.
Will be haunting the hobby shops tomorrow to see if I can find a cv like yours.
cheers
vnkiwi
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boneash

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Re: True C/V joint.for our boats
« Reply #88 on: March 14, 2013, 07:37:45 PM »

That was a brilliant build and trial, most impressed at your speed of manufacture and installation!!
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Mad_Mike

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Re: True C/V joint.for our boats
« Reply #89 on: March 14, 2013, 08:08:25 PM »

love it oldiron give yourself a pat on the back :-))
Im sure there are all kinds of solutions to this problem, it seems though so far you need  a lathe to do anything about it though.
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tt1

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Re: True C/V joint.for our boats
« Reply #90 on: March 15, 2013, 02:14:00 AM »

Well done John - well impressed, you don't hang about do you! {-)   Am following your Joffre build - will you be using your new coupling?
                                       Regards, Tony.
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irishcarguy

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Re: True C/V joint.for our boats
« Reply #91 on: March 15, 2013, 05:47:56 AM »

Hi John I had a sneaking suspicion you are a bit of a genius, I think you just confirmed it. Patent it, if Huco See's this I wonder what they are thinking now. Mick B.
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Subculture

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Re: True C/V joint.for our boats
« Reply #92 on: March 15, 2013, 06:06:49 AM »

If you look at the driveshafts of a Tamiya Frog and other cars that used the same chassis from the early to mid eighties, you will see the same dual hexagonal arrangement. The reissues use dogbone driveshafts however, as the original hexagon axels were prone to stripping.

RAAArtyGunner

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Re: True C/V joint.for our boats
« Reply #93 on: March 15, 2013, 06:22:45 AM »

love it oldiron give yourself a pat on the back :-))
Im sure there are all kinds of solutions to this problem, it seems though so far you need  a lathe to do anything about it though.
>:-o   <:(   >:-o   <:(
 
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boatmadman

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Re: True C/V joint.for our boats
« Reply #94 on: March 15, 2013, 08:32:14 AM »

Hi,

I have been following this thread with great interest and just did a quick google for rc cv joints and found these:

http://www.wheelspinmodels.co.uk/s/?q=cv+joint&x=0&y=0

Look like sensible prices to me!

Ian

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craggle

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Re: True C/V joint.for our boats
« Reply #95 on: March 15, 2013, 08:48:02 AM »

I've used these before for shaft couplings on production line equipment.


http://ondrivesus.com/pdf/couplings/double%20loop%20coupling_ondrives.pdf


No moving parts, can cope with both axial and radial misalignment and are strong enough I'm sure for spinning a small boat propeller under the water.


I have a standard plastic universal joint in my boat with the motor mounted on a soft rubber mount. It works fine but I can see improvement could be made especially in high RPM situations.


Craig.
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Mad_Mike

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Re: True C/V joint.for our boats
« Reply #96 on: March 15, 2013, 09:24:48 AM »

could work but they limited to 3000 rpm max which is the slowest of model boat prop speeds. props like that are usually around 80mm/3" in diameter. Plus i would have thought that the rubber would have been springy. I would say when ever the coupling was used at an angle, on the inside curve of the joint there would be compressional forces acting upon the rubber, which in turn being springy would fight against the revolution of the coupling, effectively trying to push back the other way. UJ's and cvs dont do this.
On a straight coupling though these would be very very quiet .
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oldiron

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Re: True C/V joint.for our boats
« Reply #97 on: March 15, 2013, 09:57:21 AM »

Thanks for the compliments gentlemen. I had thought about production of these, commercially. I don't know if there's some obscure patent on them or what it would take to get some one to produce them.
 If made commercially they could be made of Delrin plastic which is very slippery. This would reduce any concerns on friction, although I put a dab of light grease on mine to reduce an friction.

John
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irishcarguy

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Re: True C/V joint.for our boats
« Reply #98 on: March 15, 2013, 02:58:46 PM »

I must say this has been a very satisfying thread for me & the discussion & suggestions & ideas that it has produced shows how much talent is on this forum if only we would use it all the time. This time we did & look what transpired. As I have thought & actually known for as long as I have been on the forum there are a lot of talented people on here, we just need a wake up call now & then, Mick B.
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Mick B.

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Re: True C/V joint.for our boats
« Reply #99 on: June 01, 2013, 02:18:35 PM »

 Well, just to shown that Mick will put his money where his mouth is, a beautiful little CV joint arrived this morning from sunny Calgary. The whole joint is less than 50mm end-to-end and is as smooth as greased weasel-pooh. My profuse thanks go to Mick for his effort and expense. No more crummy Huco's for this guy!



 

 
 
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