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Electric EZGO Electric EZ GO Marathon, Medalist, TXT and RXV. |
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08-07-2013, 10:19 AM | #11 |
Happy Carting
Join Date: Dec 2007
Location: Southern California
Posts: 73,344
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Re: Tire size versus speed
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08-07-2013, 10:39 AM | #12 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: Tire size versus speed
Don't thank me. I'm just a hoarder, and digital hoarding is usually neater. It can still get cluttered, but at least it doesn't grow cobwebs.
I think JohnnyB is the author. |
08-07-2013, 10:53 AM | #13 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Tire size versus speed
That spreadsheet looks sorta familiar.
The PDS controller in freedom mode limits the motor RPM to about 4,400, which is about 18MPH on 18" tall tires and about 21MPH on 20" tall tires. Be aware that with the 10% gain in speed you also lose 10% in torque. ---------- If you want more torque and more speed, replace the controller with an Altrax DCX400. On stock height tires, that will up the speed to about 24MPH (~5,500RPM) with a 36V pack and about 28MPH (~6,500RPM) with a 42V pack. Word of caution: Going downhill, you can over-rev the motor with this setup and stock height tires. |
08-07-2013, 11:11 AM | #14 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: Tire size versus speed
Speaking of over-reving, have you decided out whether you motor damage was mechanical or electrical? It looks like the motor and stator windings were doing bad things to each other, but I guess that could have been mechanical.
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08-07-2013, 11:18 AM | #15 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: Tire size versus speed
I'm curious if this a a regen thing, or if I should worry about my series motor. Granted, my motor's built for high RPM, but everything has its limits, which I usually manage to find.
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08-07-2013, 11:42 AM | #16 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Tire size versus speed
Quote:
I removed the bolts holding the back of the case and the bolts holding the field windings in place and hit the output shaft with an 8lb sledge a few times, but only got the back part of the case to separate about 3/8". I might be able to get some heavy bars in that space to hold the case still while pressure is applied to the armature, or cut the back part of the case off and push it through the other way, but for the moment getting it apart is on hold while I get the cart going again. (Life has a way of interfering with fun) |
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08-07-2013, 11:49 AM | #17 | |
Not Yet Wild
Join Date: Jul 2013
Location: Ohio
Posts: 72
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Re: Tire size versus speed
Quote:
Yes yurtle, that is the chart I saw, thank you! |
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08-07-2013, 11:54 AM | #18 | |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Tire size versus speed
Quote:
My guess is that the pull of the intense magnetic field being generated added to the centrifugal forces trying to pull the armature apart and the combination of the tow succeeded in doing exactly that. I'm not sure how fast you spin your motor, but mine was spinning at about 7,600RPM when it failed, so I'm not planning on spinning my new motor quite that fast. |
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08-07-2013, 12:07 PM | #19 |
Gone Mad
Join Date: Oct 2009
Location: Buford, GA
Posts: 8,988
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Re: Tire size versus speed
I don't have Excel loaded on this machine right now, but I hit 37.6 mph with stock gears and tires. Would go faster, but I run out of hill.
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08-07-2013, 12:31 PM | #20 |
Techno-Nerd
Join Date: Jun 2011
Location: West Virginia
Posts: 19,654
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Re: Tire size versus speed
With 18" tires and 12.44:1 gears, 37.6MPH is 8,735RPM.
But Carlisle Links Tires (Typical stock) are only 17.4" tall, which is 9,036RPM!!!! That might be pushing the forces of Nature a tad. I'd give AND a call and ask them what the max recommended RPM is for your motor, which will be conservative due to the lawyer and accountants on the committee that write the specs. My guess is that a 10% to 15% fudge factor would be safe and 20% would be in the realm of reality for a relatively new motor. |
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