Author Topic: Fixed Negative Camber  (Read 492 times)

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Offline DBSMowman

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Fixed Negative Camber
« on: June 14, 2019, 04:49:50 PM »
On your axle, if using top and bottom heim joint (spherical rod end) why cut the axle with a fixed 10* of negative camber? Isn't the whole reason you spend a extra money on the heim joint is to set that adjustment manually? Seems like at max go with 3*-5* fixed camber and use heim joint adjustment there to get the exact KPI and camber you want. I was thinking of leaving the axle ends square and using the the heim joint to get the KPI and camber I want. Am I wrong here?   



Offline birdman_express

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Re: Fixed Negative Camber
« Reply #1 on: June 14, 2019, 11:54:49 PM »
Read this and see what you want to do. http://www.heymow.com/index.php/topic,425.0.html
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Offline DBSMowman

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Re: Fixed Negative Camber
« Reply #2 on: June 15, 2019, 11:36:14 AM »
Thanks for the response. I have read that write up, and read a few engineering journals on it for on road vehicles. Also some great videos on youtube by SK8215 who is pretty much an engineering genius. I don’t agree with georges write up about camber. The OEMs do it, look at the new Craftsman tight turn mowers that now have ackerman steering and negative KPI. Having a large scrub radius in turns on dirt and grass is not a good thing. Agree with him we’re running bias tires so there is a difference. At the end of the day its probably splitting hairs on something like this. I’m going to build mine square and use the chromoly heim joints to get the camber I want. I dont see any advantage to fixing camber negative if using rod ends on your spindles.


Offline birdman_express

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Re: Fixed Negative Camber
« Reply #3 on: June 15, 2019, 01:27:17 PM »
George had 20 racing mower championships in his lifetime,
Something had to be working somewhere.
Marc Baker

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Offline DBSMowman

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Re: Fixed Negative Camber
« Reply #4 on: June 16, 2019, 09:04:30 AM »
Sure, but I wouldn’t contribute those wins to 0* camber.

Offline DBSMowman

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Re: Fixed Negative Camber
« Reply #5 on: June 20, 2019, 09:18:21 PM »
I spent some time modeling this in Fusion 360 and can show here if you cut the axle end at 20* and use Carlisle Turf Masters 13X6.50-6 and Douglas 6" wheels with and offset of 6.5'' x 2.5' and a 4" x 5/8" spindle that will produce a scrub radius of 2.5" I would go with less scrub radius but I'm maxing out the mechanical capabilities of the heim joint. I'll set caster at 12*.

In short, 20* KPI, 12* caster, 2* toe-in and 2* camber. (weld spindle with static or fixed camber)

If you don't do this and put front brakes on your axle then every time you apply breaking force the wheel with the most traction will force your steering wheel to turn the opposite because of the rotational force. The negative camber will give the added benefit of providing more grip in the turns while sacrificing some on the straights. Like I said, when you're on turf or grass and going in circles it's less effective to have a large scrub radius with no camber as George has suggested. Less scrub radius and a few degrees of camber is good, even with bias ply tires. Might also be a reason why George had to shift his weight so much like he talks about when he was racing and taking corners.

Here's a CAD drawing of it to illustrate what I'm saying.

Offline DBSMowman

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Re: Fixed Negative Camber
« Reply #6 on: June 23, 2019, 07:53:04 PM »
Here it is fabricated.