Rear MAC replacement nuts and lock washers

[alfantastic]

I'm after top quality nuts to fit the axle on a rear MAC motor. The supplied nuts seem to have quite a bit of free play, and I fear that the thread will strip at some stage whilst tightening.
Also, what size should a Nord-Lock washer be for a perfect fit on the axle?

What's best, one Nyloc type nut or Nord-Lock washer and nut?

 

[dogman dan]

Most look to car lug nuts to improve the nuts. The fit, due to china machining of the axle may still be sloppy, but more threads on a wider nut will spread the force over more of the axle threads.

Not sure what the Macs take, but M12 is the size for lots of hubmotors.

 

[alfantastic]

Most look to car lug nuts to improve the nuts. The fit, due to china machining of the axle may still be sloppy, but more threads on a wider nut will spread the force over more of the axle threads.

Not sure what the Macs take, but M12 is the size for lots of hubmotors.

Thanks dogman, whatcha reckon is best, one Nyloc type nut or Nord-Lock washer and nut?

 

[dogman dan]

Lug nut.

IMO, loose axle nuts are always caused by a mis fit of the larger axle and nut on bike dropouts, or regen. Properly installed torque control devices is the key, not locknuts.

That's just my opinion. In 5 years, I had a nut get loose once, on the first half mile of riding my first ebike. If your nut is getting loose, you have problems no locknut can cure, like stripped threads, or the washer is not fitting the dropouts.

 

[spinningmagnets]

The BPM uses an 12mm X 1.25 nut, and the MAC uses an 14mm X 1.5 (M12 and M14 edited out)

edit: Just found out this post is wrong! The MAC does indeed use 14mm X 1.5, which I personally verified. But...M14 is the shorthand for ONLY the common industrial coarse thread of 14mm X 2.0

BPM is 12mm X 1.25, they are NOT the common coarse M12

 

[alfantastic]

Thanks again dogman.
I'm certainly no expert when it comes to nuts

I see that some nuts come with different figures after the M rating i.e. M12 x 1.25 or M12 x 1.50

I believe this is called the thread pitch???

If I get an M12 nut, what thread pitch do I need?

 

[alfantastic]

The BPM uses an M12 nut, and the MAC uses an M14 (14mm X 1.5).

Thanks spinningmagnets, must have posted after yours lol.

Any advantage in changing the thread size? i.e M14 x 1.5 to M14 x 1.25

edit: that was probably a really dumb question

 

[spinningmagnets]

No dumb questions, you should definitely use the same threads on the nut that the axle came with from the factory. The first number is the diameter of a cross-section of the threaded portion of the shaft. BPM has the common 12mm diameter axle. (Both the BPM and the MAC are 17mm diameter where the axles go into the motors, but the axle-ends are smaller where the threads clamp down on the bike frame).

The MAC has a 14mm diameter axle at the frame attachment point. The second number tells about how many threads there are per length of bolt. For the USA, we still often use Society of Automotive Engineers (SAE), meaning inches. In SAE, the second number is threads per inch (TPI), so a higher TPI means a finer thread (less coarse).

But...in metric measurements, it is the opposite, meaning length X thread-count (mm per one thread revolution), so a larger number = more mm per one thread. The bigger the second number, the coarser the thread.

Just learned something new, when using the shorthand "M" designation, it is only for the common industrial standard coarse threads. The MAC axle-ends are the fine-threaded 14mm X 1.5, and "M14" is a quick way to designate the common 14mm X 2.0, the BPM is 12mm X 1.25 (both personally verified).

If the pitch is the commonly-used "coarse" pitch listed in ISO 261 or ISO 262, it can be omitted (e.g., 8mm x 1.25 = M8)

 

[fechter]

I was able to find some lug nuts that fit at the local auto parts store. Another nice thing about lug nuts is they are thicker than the stock nuts so you have more threads engaged. This makes it harder to strip out the threads. I've found that if you get the nuts tight enough to start with, you won't have problems with it loosening up. Hollow axles are scary though, as you could snap it off it you go too tight. For solid axles, 40 ft-lbs is a good torque.

 

[alfantastic]

E-mailed Paul , just to verify the thread pitch on the MAC rear motor, and he sent me a schematic which states M14 x 1.25

https://skydrive.live.com/view.aspx?resid=92088474CCB8CD05!1776&app=WordPdf&authkey=!APNfLHhsrxiL7oM

Please read a few posts down the page reference this

 

[spinningmagnets]

Thanks for posting that. I recently converted a MAC to shaft-drive, and after using a custom axle I have the stock MAC axle and nuts just sitting here. I had taken them to the store I get metric bolts from, and they have one of those SAE/Metric sampler boards that allow you to insert a mystery bolt to find out the thread pitch.

Perhaps the thread was loose enough that it fit on 14mm X 1.5, even though it is actually 14mm X 1.25? This requires an investigation.

 

[alfantastic]

I was able to find some lug nuts that fit at the local auto parts store. Another nice thing about lug nuts is they are thicker than the stock nuts so you have more threads engaged. This makes it harder to strip out the threads. I've found that if you get the nuts tight enough to start with, you won't have problems with it loosening up. Hollow axles are scary though, as you could snap it off it you go too tight. For solid axles, 40 ft-lbs is a good torque.

Just out of interest fechter, were these lug nuts M14 x 1.25 as stated in the schematic in post above?
I can't seem to find automotive nuts in that size, just M14 x 1.50

 

[fechter]

The wrong thread pitch won't work. It might go on a couple of turns then sieze.
If I dig around the shop I might be able to find the package. I remember it was a pretty uncommon size, but fit something like a Porsche 911. My motor is not a BMC, but a Puma which is essentially the same thing. The axle threads might be different though. Too many brain cells died off to remember exactly. I'll try to check when I get home.

 

[fechter]

Found some here:
http://stores.ebay.com/Megapacks/Nuts-/_i.html?_fsub=3532137018&_sid=694482138&_trksid=p4634.c0.m322

 

[alfantastic]

I just want to clear up this issue with the thread pitch on a MAC rear axle.

Bought myself one of these bad boys, for a couple of quid or a few dollars:



It measures the thread pitch accurately, with a wide array of little gauges that sit in the thread grooves to determine the correct pitch.

The MAC rear motor axle thread pitch is 1.50 and not 1.25 as stated in the schematic shown above

I repeat the MAC rear motor axle thread pitch is 1.50

Hope this clears up this little saga and help members select correct nuts or dies, if they strip threads

 

[fechter]

I repeat the MAC rear motor axle thread pitch is 1.50[/color]

Hope this clears up this little saga and help members select correct nuts or dies, if they strip threads

Ah, that explains a lot. I found the lug nuts in my garage, and they are 1.5mm pitch.

From AutoZone: http://www.autozone.com/autozone/ac...l-lug-nut/_/N-25ns?itemIdentifier=223769_0_0_
$2.49ea.

 

[spinningmagnets]

Whew! (*wipes sweat from forehead). If they wanted to save money by leveraging mass-production, the lugnuts found on millions of Asian cars is about as mass-produced as they come...

 

[cal3thousand]

Thanks for getting to the bottom of this. Needs to be wiki'd

 

[alfantastic]

These got delivered and fitted today:

http://www.ebay.co.uk/itm/370592445586?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

They are deeper/longer than the original flange nut, so have around 5 more threads to grip the axle with.
The threads also start sooner within the nut, where the flange has a small part at the flange end with no threads.

The original flange nut left around 4 or 5 threads on the axle unused, but the automotive nuts use all the threads, bar 1 on the nut beyond the axle:



BTW, I have one washer and one ebikes ca type torque arm on each side of the axle.

It just feels so much more secure when tightening the nut and I'm glad I made the switch.

FYI, if anyone wants even deeper/longer nuts, then go for the tapered type. I bought both types to see which was more suitable:

http://www.ebay.co.uk/itm/280984378740?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

 

[tkollen]

If you want to make sure of not stripping your threads again please see my thread: http://endless-sphere.com/forums/viewtopic.php?f=2&t=43287&p=728181&hilit=stripped+threads#p728181