primary belt question

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ks8780
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primary belt question

#1

Post by ks8780 » Wed Mar 26, 2014 12:26 am

I am putting a Primo 1.5" belt drive on my '49 pan with a tapered sprocket shaft. I have concerns with the heavy flat washer that is mounted under the nut on the engine pulley. With the washer on I the threads come about 2/3rds of the way thru the nut. Is this enough thread engagement for the nut ? Do I dare leave off the washer ? Without the washer I have full engagement with the nut.

How tight should I get it ? All I could find on Primo's websight is 150 footpounds.

Thanks



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Re: primary belt question

#2

Post by Bigincher » Wed Mar 26, 2014 12:37 am

I've got about the same thing. I used the washer, even though the nut doesn't fully engage all the threads. I installed that setup in 1975, and it's never been a problem in all these years.

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Re: primary belt question

#3

Post by Omarine » Wed Mar 26, 2014 12:39 am

I have the same set up - same year - it's still in the box though.

What if you opened the washer enough to clear all the threads? I'd prefer to have all threads grabbing...

if my memory serves me right, I think that nut in the shaft is 80 ft lbs- dont quote me though....

150 sure sounds like a lot for a tapered shaft with roller bearings ...not sure


im sure the next few posts will finish answering this one...

cheers
oscar

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Re: primary belt question

#4

Post by bangkokbob » Wed Mar 26, 2014 1:53 am

150ft/lb should be more than enough. Don't forget the Loctite red on shaft and nut to be sure.

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Re: primary belt question

#5

Post by Bigincher » Wed Mar 26, 2014 3:04 am

That's one place a never use red Loctite. It's a left-hand thread.

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Re: primary belt question

#6

Post by Cotten » Wed Mar 26, 2014 3:09 am

Bigincher wrote:That's one place a never use red Loctite. It's a left-hand thread.
Left-hand thread on a sprocket shaft?

Not.

....Cotten

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Re: primary belt question

#7

Post by Mark44 » Wed Mar 26, 2014 7:25 am

Bigincher wrote:That's one place a never use red Loctite. It's a left-hand thread.
You're probably thinking of the nut on the clutch. It's the one that has left-hand threads. Also, the torque spec for the motor sprocket is 80 ft-lb, per the document here: viewtopic.php?f=103&t=1073" onclick="window.open(this.href);return false;. This page was published in Kirk Perry's "Mechanics and Owners Guide to 1941 - 1959 HD OHV Big Twins".

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Re: primary belt question

#8

Post by Bigincher » Wed Mar 26, 2014 1:08 pm

Yep, I'm wrong. Sorry, don't know what I was thinking. Obviously not thinking ....
But I still don't use red Loctite on it.

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Re: primary belt question

#9

Post by ks8780 » Wed Mar 26, 2014 1:24 pm

Thanks guys......that chart is helpful and the 80 foot pounds sounds more reasonable for that nut than the 150 I saw somewhere. I think I will stick to just a couple drops of blue loctite and go with that.

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Re: primary belt question

#10

Post by panhead george » Wed Mar 26, 2014 6:49 pm

You may just want to call Primo to get their blessing in case you have a incorrect part in the kit. It happens !!
Also get the name of the person you talk to and document the time and date in case the info they give you is incorrect. At least you will have a name of who you spoke with rather than "I spoke with someone there but I didn't get a name and he told me to..." It gives you a little more leverage in case there is a problem. Just sayin'

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Re: primary belt question

#11

Post by Huck » Wed Mar 26, 2014 7:16 pm

ks8780 wrote:Thanks guys......that chart is helpful and the 80 foot pounds sounds more reasonable for that nut than the 150 I saw somewhere. I think I will stick to just a couple drops of blue loctite and go with that.


Yep, I put that stuff on everything red sometimes blue always, especially on hardware that’s been worked countless times.

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Re: primary belt question

#12

Post by blewcrab » Wed Mar 26, 2014 7:28 pm

I used a large acorn nut, and I never knew how many threads extended thru. but it is still working 4 years later....knock on wood !

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Re: primary belt question

#13

Post by Cotten » Wed Mar 26, 2014 7:56 pm

Just a note on tapered shafts, Folks,..

It is the taper that holds things together.
Like a nail in oak, you are squeezing the shaft into its female taper pf tje spsrprocket, clutchhub, flywheel, or whatever, and it holds things quite securely.

The nut is basically an assembly aid, as in theory, it should all stay together without it. That's why there is a loud report when a clutch hub is pulled.
In real life, of course, shocks to the assembly, just as are used to split a taper, can occur under duress, so the nut is kept for security against a "catastrophic failure".

Let us also not forget that if the flywheels turned in the opposite direction to the way the nut tightens, it would be a greater concern. Instead, inertia works in favor of the nut.
That is why the transmission mainshaft has reversed threads, as the resistance of the drive train places inertia in the opposite direction.

...Cotten
PS: Tapers should never be lubed or loctited.
You may face a road-side repair some day.

....Cotten

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Re: primary belt question

#14

Post by panbagger » Thu Mar 27, 2014 1:52 am

I also have never used loctite on the nut of the front sprocket, and never had a problem with it. I put my nut on with an impact. My belt drive has been on there for 7 years.

Scott(panbagger)

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Re: primary belt question

#15

Post by Huck » Thu Mar 27, 2014 2:42 am

I’d be in dire straights to put an “impact” (think about it) to my motor bearings. I think he was referring to the taper itself which should be assembled clean and dry. I’ve seen them slathered in loctite, also never seize. I do what I do as follows> open belt (modern bike) items are punch marked/indexed any movement is easily detected. No such option with tins so loctite installed per the instructions hasn’t been an issue for me. I like safety wire here & there also. Most road side repairs are self induced.

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