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thompson coupling

Old 04-16-2007, 09:03 PM
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Default thompson coupling

http://en.wikipedia.org/wiki/Thompson_coupling

it would be cool if one day this becomes common... i cant seem to see whats those diagonal things on the inside but by the video on youtube it looks like it works better than a bearing-based cvd

better yet, all you gotta do is have MIP or one of the hong kong companies start churning out new driveshafts based on this,[link=http://cvcoupling.com/index.php?option=com_content&task=view&id=36&Itemid=58]their homepage[/link] says that its not that hard to make ....

Old 04-16-2007, 09:25 PM
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Default RE: thompson coupling

Wow, I really want to build a model of it now, I wish there were better pics.
Old 04-16-2007, 10:03 PM
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Default RE: thompson coupling

more information.... its basically like a double concentric universal joint, but with abit more things in it to help it work at different angles better



this is stolen from a website about helicopters apparently, hence the word 'rotorhub' in it
on our current U-joints, the problem is that the shafts dont spin at exactly the same speed... lets say that you have discs stuck on both ends of a u joint, and you bend it at an angle... if you look at one disc face on, the other disc would look like an elipse because of the angle... when you are turning the shaft (the driver shaft), the disc on the shaft your turning is spinning normally, while the disc on the other side would be like an elipse trying to follow the rotation of the pin of your side of the u-joint, it goes faster and slower every half turn

the double concentric joints is just like, another 'elipse' after the first one, at right angles, that slows down the fast parts and speeds up the slow parts, turning a final circular shape at exactly the same speed that your turning the shaft on your end... I THINK....


when you are turning this joint, it wants to straighten itself , and i assume thats what the extra bits in the thompson joint is meant to overcome and make it work with less friction...
the other way that i can see it work well, is that if the part thats represented in black in the pic is something really really really lightweight, because it is spinning like a traditional u-joint, faster and slower with every turn, and the variation in speed increases as you try to make the shaft work at greater angles

one way that i can see it, is that its good for cars and trucks using a solid rear axle... if the pinion can be mounted at an extreme angle, torque twist could be history...
Old 04-17-2007, 06:56 AM
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Default RE: thompson coupling

i kinda get how it works and it sounds good soooo how come thay dont sell them for RC cars??
Old 04-17-2007, 08:16 AM
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Default RE: thompson coupling

I would love to see these things in RC models. At first though, they would be expensive because the manufactures have to recover the initial cost shock of retooling their machines to mass produce these. Also, the requied extra machining to produce the extra parts wold keep these "CVs" generally high even after the manufactures have recovered their retooling costs.

At first, these parts would be bulky and might be feasible for 8th scale monster trucks (these are big enough to accept the bulk), but eventually, they probaly can be applied to 10th-scale on-roads as they are refined and better stronger material are found to promote mass efficientcy.
Old 04-17-2007, 08:28 AM
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Default RE: thompson coupling

imagine seeing a realy tiny ting one of these in a micro t, lol tiny.
Old 04-17-2007, 09:23 PM
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Default RE: thompson coupling

for rc cars, the only advantage would probably like being able to mount your joints at twice the steepness, which normally you wouldnt need to unless your building a crazy crawler or something...like you could have joints that rotate at 90 degrees to each other and it would feel like what we have now working at 45 degrees...

for shaft driven trucks this is going to be useful, much more freedom on where your center tranny is in relation to the other gearboxes, plus the pinions dont have to be level with the ground...

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