Reverse-mount 12V alternator

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kdiqq
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Re: Reverse-mount 12V alternator

Post by kdiqq » Thu Jul 11, 2019 3:00 pm

pinzi wrote:Or you could go for a second 24v alternator :wink:
Yeah exactly! Whatever you can find in a 10SI case, it shall bolt up.

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1977 Austrian 710M

whitesik
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Re: Reverse-mount 12V alternator

Post by whitesik » Fri Jul 12, 2019 1:55 pm

Not even close to an engineer here, but how does this tax the already meager HP of the motor? I think that has been a concern in past discussions.
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kdiqq
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Re: Reverse-mount 12V alternator

Post by kdiqq » Fri Jul 12, 2019 2:12 pm

whitesik wrote:Not even close to an engineer here, but how does this tax the already meager HP of the motor? I think that has been a concern in past discussions.
There's a couple of ways to figure that out and there are a few discussions on which is best online. From what I can find, the range is somewhere between 4 and 10HP. Since I'm using a smaller 90A alternator, Id say I'm somewhere in 6HP range. You may notice that on a 90HP motor, you might not. There are always tradeoffs with pulling accessories off engine power.

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TechMOGogy
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Re: Reverse-mount 12V alternator

Post by TechMOGogy » Fri Jul 12, 2019 2:53 pm

Lots of post here about trying to run both 24v and 12v and issue with common ground I believe.
Others here with more knowledge than I should chime in!
Dan
72 Pathfinder | 75 710M 2.7i | 96 350GDT Worker

kdiqq
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Re: Reverse-mount 12V alternator

Post by kdiqq » Fri Jul 12, 2019 3:10 pm

TechMOGogy wrote:Lots of post here about trying to run both 24v and 12v and issue with common ground I believe.
Others here with more knowledge than I should chime in!
Dan
I consulted with an electrical engineer that I work with who has built a few electric motors. He said you can try and keep the grounds split, but the alternator grounds through the case. It shouldn't be a problem. Sounds believable since there are a few guys on the military truck forums who are running dual systems with a common ground without issue.

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kdiqq
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Re: Reverse-mount 12V alternator

Post by kdiqq » Sat Jul 20, 2019 10:49 pm

Sorry for the slight delay, I got a little preoccupied helping a friend install a 3" lift... for his Miata. Really awesome project!!
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I had a bunch of trouble getting the idler how I wanted it and everything and keeping cost down, but I finally got it worked out and I'm super happy with the solution. The addition of the idler and shaft come out to about $70. A little more than I'd like, but it's beyond automotive grade with dual ball bearings and cast steel construction. Likely could have done nylon and single bearing, but I want to throw this on and forget about it.
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I modeled in a rough belt routing to demonstrate my thinking. Pulley diameters and distances are approximate, it's just for illustrative purposes.

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One question I asked when going through this was is backside tensioning a v-belt is okay. Short answer is, yes. I contacted Brewer Tensioner (who makes exceptional belt and pulley products) and they said it is doable, but may reduce belt life. The Pinz so far has awesome belt life and I'm thinking with a simplified belt tensioning method, it should be very easy to monitor and stay on top of. Testing will definitely give the best results!

I have a couple additional tweaks I want to make before this next rev hits the printer. Looking forward to getting the system going!
1977 Austrian 710M

Tjerk
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Re: Reverse-mount 12V alternator

Post by Tjerk » Sun Jul 21, 2019 4:15 am

Reverse idlers are hard on belts and some belts are possibly constructed differently than others.
On my John Deere ride-on lawnmower, the OE belt lasts twice as long as a standard Gates belt but is also twice as expensive.
Tjerk

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