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Proper way to measure a CV joint

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I have a custom project I've been working on on and off for quite a while.   While it's not a Tamiya, the axle stub portion is your standard 5mm OD so I'm looking to find a new CV axle/shaft just a little longer than this one as it has a tendency to come out of the drive cup at full droop and I think this is why the shafts are getting bent.  I can limit the down travel but this is a rock crawler project so I'd rather keep the travel as much as possible.   What measurement (from where to where) is standard for selecting these?   From the edge of the cup or perhaps the part the bearing will stop at?   Or some other measurement...????    

Thx.......

cv 2.jpg

cv 1.jpg

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My guess would be same as dog bones?  (Please do not rely on this, because I don't really know.)

That is, one centers of pin to the other center of pin. I'm assuming that the center of the CV and the dog bone would be the same.  But also, I have a strange suspicion that CV axle (wheel axle) would come in just few millimeters inward toward the chassis. I don't know why I think that. Dog bones move in and out like 5mms, but CV can't.  Somehow that makes me think that CV joint part needs to be closer to the chassis.  Again, it's just a gut feeling. I could be wrong. 

 

Looking up on some Aliexpress sellers, it looks like they are measuring pin-to-pin?  

erg3g.jpg.c58f741d7e80df729c737b9e62d139d9.jpg

https://www.aliexpress.us/item/2251832876840644.html?spm=a2g0o.detail.pcDetailTopMoreOtherSeller.1.3e643797P6SN4t&gps-id=pcDetailTopMoreOtherSeller&scm=1007.40050.354490.0&scm_id=1007.40050.354490.0&scm-url=1007.40050.354490.0&pvid=f505602c-273f-4e2c-9cec-60646a463410&_t=gps-id:pcDetailTopMoreOtherSeller,scm-url:1007.40050.354490.0,pvid:f505602c-273f-4e2c-9cec-60646a463410,tpp_buckets:668%232846%238114%231999&pdp_npi=4%40dis!USD!3.64!3.64!!!26.11!26.11!%402101e5c517098375289906557e01f9!12000025673018650!rec!US!2630314545!&utparam-url=scene%3ApcDetailTopMoreOtherSeller|query_from%3A

I'm sure you are aware of this but for future members, the the barrel inside the CVD should be in the same orientation as the pin on the dogbone end. Two silver pins should be crossing each other, not parallel. Tamiya did it the same way on Monster Beetle (like your unbent CVD). Later they changed it on Blackfoot because of vibration issues.  I've got a pair just like yours, but I'm not using them. For crawlers, it might not be a big deal, though. 

 

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I've just checked my Tamiya CVDs which are marked "70" and they are 70mm pin centre to pin centre.

On whether a CVD vs dogbone pushes things inboard a little, I've never looked at this, and it could, but a CVD could potentially get away with a little of the opposite even, since it doesn't allow play at the CVD end. Where I've upgraded a dogbone to a CVD I've searched for the same measurement CVD as was quoted for the dogbone I think (XV-01, TT-02). 

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Great info all!   Thanks.   I'll start to see what I can come up with.  

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On 3/7/2024 at 8:11 PM, BuggyDad said:

I've just checked my Tamiya CVDs which are marked "70" and they are 70mm pin centre to pin centre.

On whether a CVD vs dogbone pushes things inboard a little, I've never looked at this, and it could, but a CVD could potentially get away with a little of the opposite even, since it doesn't allow play at the CVD end. Where I've upgraded a dogbone to a CVD I've searched for the same measurement CVD as was quoted for the dogbone I think (XV-01, TT-02). 

Can I just ask @BuggyDad please - are the 70mm CVDs you quoted for the XV-01/TT-02? I'm looking for some about that length! :) 

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37 minutes ago, jonboy1 said:

Can I just ask @BuggyDad please - are the 70mm CVDs you quoted for the XV-01/TT-02? I'm looking for some about that length! :) 

Ah no, these are 70mm for just the swing shaft, not the total length, for various buggies including the DT-03 and I hope (some discussion there!) the Boomerang. XV-01 uses, I believe, 42mm fronts and 39mm rear? 

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2 minutes ago, BuggyDad said:

Ah no, these are 70mm for just the swing shaft, not the total length, for various buggies including the DT-03 and I hope (some discussion there!) the Boomerang. XV-01 uses, I believe, 42mm fronts and 39mm rear? 

sorry - i worded that question all wrong! :rolleyes:

I'm after some CVD's (or dogbones) where the pin to pin length is about 70mm. I've got some outer XV-01 hub axles and I reckon some 70mm long pin to pin dog bones should be about the right length to fit what I am after.

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33 minutes ago, jonboy1 said:

sorry - i worded that question all wrong! :rolleyes:

I'm after some CVD's (or dogbones) where the pin to pin length is about 70mm. I've got some outer XV-01 hub axles and I reckon some 70mm long pin to pin dog bones should be about the right length to fit what I am after.

Oh right. Well, the ones I've been buying are Tamiya 53791, but they are the full set, swing shaft and axle. I couldn't tell you whether the axle goes with the XV-01 hop-up CVD axle but it's a common length one, not the short one used in TD4. You won't be able to use a CVD swing shaft with an axle that's designed for a dog bone, but perhaps a hotshot series dog bone (not sure which - there are some slightly different lengths) might suit, since 53791 is quoted as a Boomerang hop-up. In fact, when I build my Boomerang I'll probably have some of these going spare I would happily send you, it's just it might be some weeks before I know (because need to confirm I can use the CVDs). If you want, I can have a look in the kit later and measure them. 

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1 hour ago, jonboy1 said:

I'm after some CVD's (or dogbones) where the pin to pin length is about 70mm. I've got some outer XV-01 hub axles and I reckon some 70mm long pin to pin dog bones should be about the right length to fit what I am after

I found 70mm CVD swing shafts under #19805979 - they are listed as spare to #53791 set @BuggyDad mentions.

The same CVD set is meant for DF-03, which uses #19805551 - so if you're looking for dogbones, those should be the length you're looking for.

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39 minutes ago, BuggyDad said:

Oh right. Well, the ones I've been buying are Tamiya 53791, but they are the full set, swing shaft and axle. I couldn't tell you whether the axle goes with the XV-01 hop-up CVD axle but it's a common length one, not the short one used in TD4. You won't be able to use a CVD swing shaft with an axle that's designed for a dog bone, but perhaps a hotshot series dog bone (not sure which - there are some slightly different lengths) might suit, since 53791 is quoted as a Boomerang hop-up. In fact, when I build my Boomerang I'll probably have some of these going spare I would happily send you, it's just it might be some weeks before I know (because need to confirm I can use the CVDs). If you want, I can have a look in the kit later and measure them. 

Thanks very much @BuggyDad and @Honza that's super helpful of you :) 

So, to cut a long story short (I decided not to do a full build on this as I don't think anyone would be that interested so don't want to start one here) I'm building a bit of a bitsa and have provisionally placed the gearbox and the outer hubs where I want them, and I thought I had worked out the length of the dog bones and ordered some off aliexpress. They arrived and.... didn't fit by a nautical mile. I measured again, and then again, scratched my head, measured again, did a bit of basic math and found myself flummoxed. I checked what I ordered this morning and discovered it is completely different from what arrived, so I'm super mixed up as to what I think I need, what I have and what is actually available. 

What I should do now is stop being lazy and actually model the outdrive and outer hub axle in my assembly and get a proper measurement. What I will probably do though is print out the manual page for the boomer with the dog bone on, cut it out of cardboard and see how it fits.... :ph34r:

Knowing that 70mm ones are out there in Tamiya world is invaluable though, as I can probably tweak bits to make this fit, so for that info I am very grateful :) 

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3 hours ago, Honza said:

I found 70mm CVD swing shafts under #19805979 - they are listed as spare to #53791 set @BuggyDad mentions.

The same CVD set is meant for DF-03, which uses #19805551 - so if you're looking for dogbones, those should be the length you're looking for.

Ah now that's great to know. I will pick some of those swing shafts up as spares. They can be had for £5/pair on ebay I see. 

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