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Rear Suspension and Half-Shafts

Printed From: Official Baja SAE Forums
Category: General
Forum Name: Design Discussion
Forum Description: Discuss Design, Tech, Cost, and related issues
URL: http://forums.bajasae.net/forum/forum_posts.asp?TID=2667
Printed Date: Jun/25/2019 at 2:21am


Topic: Rear Suspension and Half-Shafts
Posted By: kelleybe
Subject: Rear Suspension and Half-Shafts
Date Posted: Dec/28/2017 at 4:13pm
To anyone that can help...

I'm designing the drivetrain, and our suspension guy is not around (winter break).  I need to keep making progress on our design, and all I know is that he said he would need about 1" of plunge at full compression. Attached are some pictures from SolidWorks of basic linkage drawings (Lotus never responded and we do not know who to contact).

We decided to design for CV half-shafts, and develop and test against a u-joint style shaft design (if we have time).  I need some guidance here on the articulation/operating angle.





In the picture, with the full articulation "arc" (not sure here if plunge is taken into account) we have about 34 degrees.

I've read that most off-road axles can, but shouldn't for extended periods, handle around 28 degrees, and that 25-30 degrees are considered high angles.

Should we take the operating angle to be from the centerline of the output shaft of the gearbox to the CL of the shaft when at ride height?


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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!



Replies:
Posted By: bracer
Date Posted: Dec/29/2017 at 11:59pm
I would believe that you have explained the operating angle correctly, and assuming that it is at ride height. But the angle that you are expressing interest in, the 28*, should be +- 28* from the shaft to the shaft of the bell. Word of advice, make sure to check the outboard bell as well as the inboard bell.

In the past, we have set up sensors and a motion study in SW to measure the angles and length of the shaft between the two CV points to verify on an excel graph that our shaft would be within limits.

This year, we have switched to Shark suspension modeling, and was able to give us the data for the shaft with only defining the CV points. This might help depending on what you're running for suspension software.


Posted By: kelleybe
Date Posted: Dec/31/2017 at 9:46pm
I think we're going with aftermarket Polaris Ranger axles (Sixity XTA) that can handle a 40* drive angle, but I am not sure if that is 40 each way, or 20 each way, they did not specify and have not gotten back with me yet.

Also, I tried contacting the tech support for Lotus again and I am waiting to hear back from them. How exactly did you guys get your hands on Shark?


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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!


Posted By: bracer
Date Posted: Jan/01/2018 at 12:14pm
After checking over our own shaft specifications, the angle that they specified as 40* is each direction. Putting this into driveline terms, it can handle 40* of droop, and 40* of compression.

Checking with the suspension team, Shark is from Lotus, so I am not sure of the differences between our versions.


Posted By: kelleybe
Date Posted: Jan/01/2018 at 12:21pm
Thanks for the insight. We're probably going to order that shafts as long as we can get them, but we'll probably have to cut, balance and weld in sections.

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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!


Posted By: kelleybe
Date Posted: Jan/04/2018 at 10:09pm
Anyone know how to read the Plunge/Angle Diagram, and what it means?

file:///H:/2017-2018%20Baja/Drivetrain/Polaris%20CV%20Shaft%20Data/half_shaft_spline_data.pdf


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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!


Posted By: Adam_Clark
Date Posted: Jan/05/2018 at 7:33pm
Try to get your axles as soon as you can. We have run into issues with the max angle a cv axle can do. The non-plunging joint tends to be able to do 40* of droop and 40* of rebound, but we were unable to source a plunging joint that was above 28* each way. It was a large source of suspension and drivetrain redesign issues this season. I would recommend seeing if you can go to an AVT supplier and just try out their stock. If you are running no plunge on the outboard or the inboard joints 40* in both directions is more than fine for most axles. Goodluck!


Posted By: kelleybe
Date Posted: Jan/05/2018 at 7:46pm
The axles are on their way, unfortunately I think the splines stub shafts are too big for my design, so I'll have to contact the company and get exact specs.

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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!


Posted By: RLM
Date Posted: Jan/05/2018 at 8:40pm
https://www.polarissuppliers.com/sae_team/half_shaft_spline_data.pdf

Are these the plunge diagrams you are referring to?
if so, what are you struggling with?
they show the max plunge the axle can hansle based on the angle between the cup and the axle shaft.


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McMaster Baja Racing (09-Dec 2015)
Team Captain 2012-2015
Suspension Lead 2015-2016
All spoonfeed PM requests will be billed at $10 USD per reply, payable via paypal.


Posted By: kelleybe
Date Posted: Jan/05/2018 at 10:45pm
Those are the ones. Is it the plunge angle versus the amount of plunge from the center line? Also am I correct in assuming that they all have 1.6 in of plunge since that's what the graph says?

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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!


Posted By: Mohit Yadav
Date Posted: Jun/27/2018 at 1:24pm
Hi, Did you get any CV joint with with both plunging and articulation angle greater than 40 degree? can you provide details regarding this.


Posted By: kelleybe
Date Posted: Jun/27/2018 at 1:39pm
We ended up going with Polaris sportsman 500 axles from Sixty.com. we broke all sets (torqued in half) due to too small of a rear track, and high drive angle (use a greater width than 48" or this might happen to you). The plunge was fine, but I would recommend finding the smallest CV joints you can find. Lots of teams not using custom yoke style shafts use modified Polaris axles for the CV joints, but we had no luck finding the specific joints that are very small (~2") compared to ours were fairly large (3" diameter) and heavy (17lb for both axles)

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Driveline Design '17-'18 Raider Racing

You silly? I'm still gonna send it!


Posted By: RLM
Date Posted: Jun/28/2018 at 8:09am
check out the front axles from the RAZR

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McMaster Baja Racing (09-Dec 2015)
Team Captain 2012-2015
Suspension Lead 2015-2016
All spoonfeed PM requests will be billed at $10 USD per reply, payable via paypal.



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