CV's instead of half-shafts...
01-29-2012, 10:03 PM
#21
Le Mans Master
Thread Starter
Steve, the specific suspension geometry involved in adding an additional link, tho relative, is simply NOT the topic of this thread; rather IMHO it's a stand-alone subject whatever type of half-shafts or CV's one may have. Besides, I don't think anyone is arguing against optimizing it for a given vehicle (which isn't a one-size-fits-all proposition, btw). If you feel so compelled to engage in a discussion of suspension geometry and vehicle dynamics, why not open a thread on the subject (post a link here) and we can talk about it, ad nauseum. That said, I'd suggest bringing more to the table than your take on SLA 101.
01-29-2012, 10:29 PM
#22
Tech Contributor
Member Since: Jun 2004
Location: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Posts: 18,367
Received 771 Likes
on
553 Posts
In trade school you were taught the theory as well as the practical. I happened to be the guy that stayed awake during those sessions because I found it interesting. Well, Steve, believe it or not, in engineering school we were actually taught some practical stuff too. That is the theory that was taught. I believe it to be accurate for a few reasons.
1. It's in the text book we used.
2. Only one wheel is behaving like the ideal with the unequal arm setup. The other is leaning the wrong way. The outside wheel (of the corner) is leaned into the corner, but the inside wheel is leaned away from the turn, exactly opposite what we would like.
3. When this design was developed and first being used (1930's) the quality of the roads and the speed of the cars was such that designing camber change to lean into a corner would not have been a major consideration. Tire wear would have been.
Kaos,
Both control arms are moving inward because their outer ends travel in arcs as they go up and down. The lower moves inward for the same reason the upper moves in. As you move through the arc it moves toward centre. The shorter arm above moves inward more than the longer because it cuts a tighter circle. That's the principle of unequal arms. In equal arms they both move the same amount and the wheel stays straight and both pivots move inward the same amount.
However, when the top moves in more than the bottom the bottom of the tire pivots out on the lower outer pivot point. The design is that the bottom of the tire kicks out exactly as much as the lower joint is moving it in, resulting in 0 track change.
I don't question for a minute that your car handles great. I just think that the optimum setup might be where all these things are considered.
Skunk Works,
With all due respect, any discussion about u-joints vs CV joints is redundant without a replacement upper control arm. And any contemplation of that replacement needs to discuss the geometry. A discussion about which is stronger, a ball and trunnion or a cross and roller slip yoke combo, is not a discussion about replacing u-joints with cv joints. I didn't believe I was off topic here.
Steve g
1. It's in the text book we used.
2. Only one wheel is behaving like the ideal with the unequal arm setup. The other is leaning the wrong way. The outside wheel (of the corner) is leaned into the corner, but the inside wheel is leaned away from the turn, exactly opposite what we would like.
3. When this design was developed and first being used (1930's) the quality of the roads and the speed of the cars was such that designing camber change to lean into a corner would not have been a major consideration. Tire wear would have been.
Kaos,
Both control arms are moving inward because their outer ends travel in arcs as they go up and down. The lower moves inward for the same reason the upper moves in. As you move through the arc it moves toward centre. The shorter arm above moves inward more than the longer because it cuts a tighter circle. That's the principle of unequal arms. In equal arms they both move the same amount and the wheel stays straight and both pivots move inward the same amount.
However, when the top moves in more than the bottom the bottom of the tire pivots out on the lower outer pivot point. The design is that the bottom of the tire kicks out exactly as much as the lower joint is moving it in, resulting in 0 track change.
I don't question for a minute that your car handles great. I just think that the optimum setup might be where all these things are considered.
Skunk Works,
With all due respect, any discussion about u-joints vs CV joints is redundant without a replacement upper control arm. And any contemplation of that replacement needs to discuss the geometry. A discussion about which is stronger, a ball and trunnion or a cross and roller slip yoke combo, is not a discussion about replacing u-joints with cv joints. I didn't believe I was off topic here.
Steve g
01-29-2012, 10:40 PM
#23
Steve, the specific suspension geometry involved in adding an additional link, tho relative, is simply NOT the topic of this thread; rather IMHO it's a stand-alone subject whatever type of half-shafts or CV's one may have. Besides, I don't think anyone is arguing against optimizing it for a given vehicle (which isn't a one-size-fits-all proposition, btw). If you feel so compelled to engage in a discussion of suspension geometry and vehicle dynamics, why not open a thread on the subject (post a link here) and we can talk about it, ad nauseum. That said, I'd suggest bringing more to the table than your take on SLA 101.
Are you wanting to build a luxury 6 seater or a sports car.
Gee, you say a previous thread on this topic went south too? Go figure.
Steve g
01-29-2012, 10:47 PM
#24
Hey, we're all here looking for answers, aren't we?
Steve g
01-29-2012, 11:31 PM
#25
Le Mans Master
Thread Starter
Dang it, now I'm doing it too.
I guess if nobody want's to talk about the CV's a sidebar on geometry might at least keep the thread bumped for a while.
01-29-2012, 11:36 PM
#26
Le Mans Master
Thread Starter
Steve, I don't have any problem with relevant issues directly concerning CV's being brought up, as I don't pretend for a minute to know everything about them. I'm just trying to keep the main topic of possibly doing the CV mod from getting lost in the mix, relevant as may be surrounding issues. Geometry wasn't intended to be front and center here, however much you may want to put it there.
Last edited by TheSkunkWorks; 01-29-2012 at 11:39 PM.
01-30-2012, 01:35 AM
#27
Steve, I don't have any problem with relevant issues directly concerning CV's being brought up, as I don't pretend for a minute to know everything about them. I'm just trying to keep the main topic of possibly doing the CV mod from getting lost in the mix, relevant as may be surrounding issues. Geometry wasn't intended to be front and center here, however much you may want to put it there.
I presumed the title of CV vs u-joint was referring to replacing the fixed length half shaft, which is the upper control arm, with a shaft of variable length such as is used on most front wheel drive cars which is commonly referred to as a CV (constant velocity) joint. Fairly presumptuous on my part because there are other designs of constant velocity joints that do not use a ball and trunnion and are not variable length.
However, under that assumption, the question I saw (right or wrong) was , how do you vary the length of the shaft? I see two options, cross and rollers with a slip yoke or ball and trunnion (what I believed you meant by CV joint). To me, that doesn't involve a very deep discussion and there is no clear advantage of one over the other. But it's the least of the decisions you have to make.
The change from a system using the half shaft as the control arm to introducing a third supporting member is huge. This to me is the challenge. What type of joint you use is like deciding what color it should be. And before anyone takes on a project like that they should have an idea as to what it involves. And from the reading I've done on this forum it appears that this is a topic that needs discussing.
So, if I misinterpreted, set me straight. Maybe you had a fixed length halfshaft with a cv joint in mind and didn't anticipate any major suspension change.
Steve g
01-30-2012, 01:33 PM
#28
Le Mans Master
Thread Starter
Due to the direction the previous thread had gone, I felt it a good idea to limit the scope of this thread strictly to modern prop-shafts, as commonly referred to as CV's in layman's terms and of the type similar to those utilized in late generation Corvettes, and incorporating them into the C2/C3 chassis.
Suspension design, tho one would obviously have to undertake developing and install a proper additional member in order to replace the half-shafts as the upper link (going with CV's isn't the only reason one might do that), is IMCO a topic best left unto itself. I'm not saying such isn't important or unnecessary, rather that including such complexities as suspension theory here can very easily swamp the topic at hand (much as has this very discussion about it swamping the topic...).
If I had any questions about suspension geometry relative to this topic, I would have asked them. I don't, so I didn't. Thing is, Steve, by the nature of your recent posts on the subject (here and elsewhere) I feel you're assuming everyone needs elementary schooling in the matter to keep us from getting in over our heads. (Hope my own previous posts regarding suspensions haven't come off like that.)
On the one hand, many of us have studied and/or worked in the field with suspension geometry and setup for a good number of years (since the late '70's in my case), and already have somewhat of a background on which to rely. On the other, many may only want to know what to do without burning out their grey matter over the theory behind it. And, there are plenty of those who fall in between, but attempting to educate them here would very likely be in the way IMCO, as that's far more involved.
That we may have a better chance to learn something worthwhile about the original topic itself, maybe I'm being thick about it, but I request again that we stick to it specifically, and consider the fact that re-engineering suspension geometry and/or components would necessarily come into play as being established and read. And, as I said earlier, feel free to open a thread on suspension geometry and post a link here, and we can talk about it until the cows come in.
OMG, we're 28 posts in and have barely scratched the surface on CV's.
Is there a lack of interest altogether, or is there just that little to say about them in the first place that hasn't already been brought up?
Suspension design, tho one would obviously have to undertake developing and install a proper additional member in order to replace the half-shafts as the upper link (going with CV's isn't the only reason one might do that), is IMCO a topic best left unto itself. I'm not saying such isn't important or unnecessary, rather that including such complexities as suspension theory here can very easily swamp the topic at hand (much as has this very discussion about it swamping the topic...).
If I had any questions about suspension geometry relative to this topic, I would have asked them. I don't, so I didn't. Thing is, Steve, by the nature of your recent posts on the subject (here and elsewhere) I feel you're assuming everyone needs elementary schooling in the matter to keep us from getting in over our heads. (Hope my own previous posts regarding suspensions haven't come off like that.)
On the one hand, many of us have studied and/or worked in the field with suspension geometry and setup for a good number of years (since the late '70's in my case), and already have somewhat of a background on which to rely. On the other, many may only want to know what to do without burning out their grey matter over the theory behind it. And, there are plenty of those who fall in between, but attempting to educate them here would very likely be in the way IMCO, as that's far more involved.
That we may have a better chance to learn something worthwhile about the original topic itself, maybe I'm being thick about it, but I request again that we stick to it specifically, and consider the fact that re-engineering suspension geometry and/or components would necessarily come into play as being established and read. And, as I said earlier, feel free to open a thread on suspension geometry and post a link here, and we can talk about it until the cows come in.
OMG, we're 28 posts in and have barely scratched the surface on CV's.
Is there a lack of interest altogether, or is there just that little to say about them in the first place that hasn't already been brought up?
Last edited by TheSkunkWorks; 01-30-2012 at 02:06 PM.
01-30-2012, 02:04 PM
#29
Instructor
Member Since: Jul 2008
Location: Wertheim Baden-Württemberg Germany
Posts: 123
Likes: 0
Received 0 Likes
on
0 Posts
Half shafts,and the idea of using the idler shaft in my differential as an axle stop never appealed to me anyway.
I repaired a C3 for a friend of mine,after a "euro compact" tagged the right side B post,and wiped out the TA.After it was back on the road we noticed the diff really making noise.Tore it down and found the idler pin bent to death and the left side yoke had the "C" clip groove ripped out.An extra link will not prevent this in the event of an accident,but it will relieve the stress exerted inside the diff when the yoke is pushed in during "normal" driving.
I really don't think it would be complicated at all to add ,say, strut rods to the top sides left.Mount them in a negative angle to the bottoms so that the camber changes that already exsist in the suspension travel stays the same.
Heck it ain't rocket science.
Last edited by Ravoll; 01-30-2012 at 02:20 PM.
01-30-2012, 02:20 PM
#30
Le Mans Master
Thread Starter
Ravoll, you can apparently remove the inner yoke C-clips and allow the OE type half-shafts to float, as long as you add a new upper link.
For the record, my own desire to relieve the half-shafts of their duty as upper links is more about changes to the suspension I wish to make, rather than about changing the suspension just so I can have CV's. I just figure while I'm at it (if I can ever afford it), since I already have flanged inner yokes, why not think about going with the state of the art.
For the record, my own desire to relieve the half-shafts of their duty as upper links is more about changes to the suspension I wish to make, rather than about changing the suspension just so I can have CV's. I just figure while I'm at it (if I can ever afford it), since I already have flanged inner yokes, why not think about going with the state of the art.
01-30-2012, 02:54 PM
#31
Drifting
I considered both but saw that the movement was small. I also saw ujoints used on some C3 roadracers.
Local driveline shops built the halfshafts up easily as I used stock u joints at both ends.
This is my version below
Local driveline shops built the halfshafts up easily as I used stock u joints at both ends.
This is my version below
01-30-2012, 04:52 PM
#32
Le Mans Master
Thread Starter
Not CV's, but nice suspension re-work Dave. 
Modded C2/C3 TA's or all new "uprights"?
The thought is disappointing, but starting to sink in that perhaps going to CV's only makes sense in the event one is starting over with an entirely new rear suspension/driveline setup which already incorporates them. Anyway, I'm sure there's someone out there who could do a set that would work, who hopefully wouldn't charge both an arm and a leg.
Modded C2/C3 TA's or all new "uprights"? The thought is disappointing, but starting to sink in that perhaps going to CV's only makes sense in the event one is starting over with an entirely new rear suspension/driveline setup which already incorporates them. Anyway, I'm sure there's someone out there who could do a set that would work, who hopefully wouldn't charge both an arm and a leg.
01-31-2012, 01:25 PM
#33
Drifting
All new uprights built for the project. I used a monoball for the top pivot.
I may used C5/C6 uprights in the future that would allow me to use ball joints. This would also allow for C5/C6 hub and CV joint at the wheel end.
I may used C5/C6 uprights in the future that would allow me to use ball joints. This would also allow for C5/C6 hub and CV joint at the wheel end.
Dave, I want to be just like you when I grow up.
02-14-2012, 05:03 PM
#36
Le Mans Master
Thread Starter
From what I've been able to come up with when looking into this previously, one may well be able to order plenty stout enough CV's from specialty aftermarket resources with the correct length, plunge and possibly with ends which will mate directly up to the OE outer spindle flnages. In my case, my inner yokes are also flanged (12-bolt IRS) with the same pattern, and so if I find a match for one end I've solved them both. Other than that, I'm not sure what all anyone ought best to understand about CV's (previous discussion of indirectly related issues aside) before going that route.
04-20-2012, 12:56 PM
#37
Digging up an old thread because I've wondered about this too. The thompson CV joint will tolerate large lateral loads without pulling apart, unlike the CV joints we see on most cars.
The fact that the C2,C3, and C4 (plus the Jaguar E-types) gain camber and have toe that doesn't remain constant means the u-joints are routinely operating out of 90° parallel to each other. That equals vibration.
I would very much like to see a PST or Denny's develop a half shaft with thompson couplings or something similar that could do away with u-joints.
The fact that the C2,C3, and C4 (plus the Jaguar E-types) gain camber and have toe that doesn't remain constant means the u-joints are routinely operating out of 90° parallel to each other. That equals vibration.
I would very much like to see a PST or Denny's develop a half shaft with thompson couplings or something similar that could do away with u-joints.
08-03-2012, 05:27 PM
#38
Melting Slicks
The topic of CV's was opened recently, albeit by a noob [sic] with attitude issues, however the thread has unfortunately deteriorated into an argument between U-joint vs. CV. So, for anyone interested in actually discussing possible replacement of the half-shafts with CV's, feel free to chime in with constructive input. And, for the sake of this discussion, anyone opposed to this type of mod please just look the other way and leave us to it. Thank you.
TSW
TSW
08-03-2012, 07:14 PM
#39
Le Mans Master
Thread Starter
Ok so I am not a writer or tech term guru, but the tude was in result to replys that did nothing other than insult. Something as simple as an idea can inspire progress, despite the count of my post. I read many forums and been a member to them for many years and all of my user names on them have low post counts. I choose to only ask somehting if I cna't find the answer or add to a topic if I think it's useful to the OP.
FWIW, and that's most likely nothing to you sort, I've since learned a great deal about the specific issue in question of CV's, but haven't seen the point in updating...
IBTL
