On my Ralt RT5 the rear wheel hubs are located slightly forward of the differential centerline causing the axles to be angled forward from the inner CV joints to the outer CVs. Was this designed this way for a purpose other than meeting a wheel base dimension? Since I have to build a new diff carrier to install the Hayabusa I figure now is a good time to change to a geometry that would allow for straight axles if it would be more desirable.
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Scott Woodruff
83 RT5 Ralt/Scooteria Suzuki Formula S
65 FFR Cobra Roadster 4.6 DOHC
I am not too familiar with the RT5 - ask Russ - but the axles should be pretty much perpendicular with the chassis centerline. This can be affected by the adjustment of the forward leg of the lower A arm. I have seen this sometimes when someone tries to get as much caster as possible and they pull the lower link as far forward as possible.
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Charlie Warner fatto gatto racing
Now after I looked at it again I see the hubs are actually located aft of the diff centerline by about an inch. The upper arms are nonadjustable rockers & the lower arms are rigid A arms with the rodends adjusted evenly, so I would think the 1" offset was designed into the car. Anyone know if rear suspensions are purposely offset, like driveshafts on front engine vehicles, or can I improve it by locating the diff carrier aft to line up with the hub centerlines? Doing this would also help with more clearance for the drive chain to the rear sprocket.
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Scott Woodruff
83 RT5 Ralt/Scooteria Suzuki Formula S
65 FFR Cobra Roadster 4.6 DOHC
There is a possibility that the lower wishbones are actually on the wrong side. On mid 90's Van Diemens the lower wishbones are nearly symmetrical, but not quite. Installing them on the wrong side results in the caster being off and the driveshafts being mis-aligned.
Assuming you dont have this issue then I would say you are best off putting your diff such that the driveshafts are perpendicular at normal ride height. This results in the least amount of CV joint wear and least power losses, even if it is small.
It is very common for drive shafts to sweep back. It is usually done to shift some weight to the front for handling purposes.
CVs do not want to be run square to the diff (ie - no angularity fore-aft or up-down) - the balls need to run back and forth a bit every revolution to keep from fretting the races.
I would think the variations in angularity caused by the normal vertical movement of the axles due to normal ride changes would suffice for this purpose.
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Charlie Warner fatto gatto racing
Thanks to both of you for the info. Since the halfshafts are not perfectly horizontal when the car is at rest I would think it would be fine to build it with zero fore/aft angle & let the horizontal angle take care of the ball rotation.
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Scott Woodruff
83 RT5 Ralt/Scooteria Suzuki Formula S
65 FFR Cobra Roadster 4.6 DOHC
And just how small a percentage of the total track time would this be?
Hardly matters - the fact that without angularity the balls will just sit in one spot and vibrate against the races is what the CV manufacturers such as GKN (Lobro) recommend strongly against allowing to take place.
How about using a Tripod joint instead of a Lobro. No balls to rattle around, what lubrication needs to take place is done with the movements of the suspension. Also, the tripods can be lighter for the same torque transmission.
Having checked with some other RT5 owners I would do as Craig suggests and make sure the lower A arms are not upside down. They are double sided but not symmetrical. It should only take a few minutes to pull one and compare it to the other side to see if by flipping it over you can move the outer link to locate the upright so as to better align the half shaft.
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Charlie Warner fatto gatto racing
And, I submit in this technically esoteric discussion that it is virtually impossible for that to happen in a dynamic environment.
You would think so, and it is, but only up to a point. A few designers in the past - both road cars and race cars - found out the hard way that CV life will be shortened considerably when the design was such that there was almost no angularity in either direction at normal operating life. A lot naturally depends on how close to maximum capacity it is being stressed, the high-pressure film strength of the grease being used, as well as the change in angularity during those movements - and on a car such as the RT5, those movements are very small indeed.
Which is why the manufacturers recommend against such designs.
Okay, since I have spare lower A arms it was easy to check. It turns out they are identical on both sides of my 83 RT5, just flipped over on one side. Also, if they were flipped over & installed on the same side it would cause the hub centerlines to be positioned even more aft & the halfshafts to be angled even more. So, Im' still thinking with the halfshafts naturally angled up from the inner to outter CVs I should be good with no lateral angles. Anyone disagree?
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Scott Woodruff
83 RT5 Ralt/Scooteria Suzuki Formula S
65 FFR Cobra Roadster 4.6 DOHC
If the legs are installed properly on the car (if you don't know they were re-epoxied in the last year then do it yourself!), the right year A arms are used, and the lower tub-to-gearbox adaptor fits properly the odds are great that your configuration is proper. Set the suspension up with the factory nominal settings and see where the half shafts are. From memory they should be around .5 degree negative camber, equal and positive caster (no number specified) and 1/8 total toe in. Try settting the caster at zero and see what happens.
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Charlie Warner fatto gatto racing
General Formula Car Discussion
rear axle angles?
