GoldenMotor.com Forum
General Category => Magic Pie & Smart Pie Discussions => Topic started by: wattsup on May 21, 2011, 09:06:37 PM
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hi, does anyone know the thread size of the majic pie 1000w 48 v axle shaft, and is it metric, imperial or chinese, the nuts supplied with mine wobble on the thread of shaft and I want to replace them with a better fit if possible, as they do not inspire confidence to stay tight
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send a pm to webby, he got some replacement nuts recently , should be able to help ;D
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I'm pretty sure they are M14 x 1.5mm, but I could not find stainless domed nuts in that size to fit mine.
(http://www.proboat.co.uk/uploaded_images/Nuts_dome_nut.jpg)
Alan
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thanks, as usual this forum comes up trumps on helpfullness, cheers guys !
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Hi wattsup,
Try the local car-tyre shop.
I got my extra nuts there for free. :D
Usualy they got a box with all kinds of bolts and nuts.
14x1.5 is the size.
Erik
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Hello Mate
I think they are 14mm (locking nuts) but I took the old one with me when I went to the merchants near where I live and he got the right ones for me.
I'm happy to post you my 2 spare that I have if you like? There only a few pence each so don't need to worry about money or anything. I not back to the UK until Tues evening 24th May.
When I get some more next time I will remember what size he said.
Anyway let me know if you want mine.
Webby
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thanks for the offer webby but no need bud, as i,ve already bought some from fleabay. my next challenge are the torque arms and some soldering, as i,ve shortened and tried to tidy my wiring. I will post pictures of my build. thanks again all.
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the thread size is NOT 14mm 1.5mm pitch, it is; 14MM X 1.25MM METRIC FINE
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the thread size is NOT 14mm 1.5mm pitch, it is; 14MM X 1.25MM METRIC FINE
You must have a different axle to mine, as my Magic Pie is definitely M14 x 1.5mm, I couldn't lay my hands on my pitch gauge so I set my vernier gauge at 15mm and it lined up across the top of ten threads exactly (1.5mm pitch)!
M14 x 1.0mm, M14 x 1.25mm and M14 x 1.5mm are all referred to as as metric fine, whereas M14 x 2.0 mm is metric coarse.
If you could measure across the top of ten threads, you should be able to confirm whether it's 12.5mm or 15mm.
Alan
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could not do it with vernier, about 13mm across 10
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i bought some 1.5 pitch nuts and they would not screw on to 1 thread even. webby sent his spare ones to me as I pm, ed him , they screw right on good without wobbles
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I've checked again, and the only details I could find from GM relating to axle threads was for the HBS hubs, which are clearly marked as being M14 x 1.5mm.
(see attachment)
From your measurements, it would appear that they have changed to a finer pitch on some axles.
Alan
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my motor, 1000w 48v majic pie external controller, was purchased,26/04/2011. the m14 part is correct, but not 1.5mm, because as mentioned, this pitch wont screw on 1 thread. it appears that you may be correct about thread change. anyway my problem is now solved to a satisfactory conclusion, thanks alan.
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I've had this problem too. I bought some M14 1.5 'half nuts' and they didn't fit. I've just been too embarressed to mention it 'cause I thought you all might laugh at me :-[
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dear andrew, don,t you feel like a great weight has been lifted off your shoulders! coming out like you have, it must have been difficult living with the burden, and I feel for you. bet you feel great now.......feel the love ;)
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Yep, now i've just got a pack of M14 nuts with no purpose, I feel cheated.
a problem shared is a problem halved!
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likewise
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Sorry to bump such an old thread but does anyone know the axle nut size on a pro 901 rear? I was putting on some new rubber and stripped one side of my axle. I had a torque wrench on it set to 55lbs??? I don't understand how 55lbs can strip it but it's done now.
I guess I can re thread it and get a new nut but I've never really done this before. Can I just clean the threads and put a new nut the same size on or do I need to totally redo the threads and get a smaller nut?
Any advice would be great.
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i have done this with other bolts not the magic motor ones. the easiest way I found is sae and metric are very close in size. find the sae nut that is just a hair to small to thread get the proper size die and re thread the axle. then use the appropriate size nut for it and you should be all set. do not try to re thread with the nut. die's are not that expensive and most hardware stores you can buy just one die and not have to buy a complete tap and die set
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The thread size on my MPIII was 14mm with a 1.5 pitch. I went to the local auto parts supplier and found the the correct nuts there. I put them on backwards with the tapered ends out. You might check my earlier post on stripped axle on MPIII (http://goldenmotor.com/SMF/index.php?topic=4583.msg26625#msg26625).
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Thanks for the fast reply guys, I ended up putting the nut on backwards like jbc@ did and it grabbed the thread good enough for now until I can get it fixed properly. I also marked the nuts and frame with a red permanent marker so I can monitor it closely if it decides to back off or move on me in the meantime.
I have lots of good thread under my torque arm and on the end of my axle so I have a few options that should only require cleaning the axle threads as best I can and getting a few original replacement nuts.
I would really appreciate your guys opinions on this if maybe one way is safer then another or something... My current setup on stripped axle side is like this ( Rear hub )... Bike dropout > tabbed washer > GM tourqe arm > axle nut.
So I figure I can either,
A: Clean axle threads as best as I can, and go Dropout > tabbed washer > new axle nut > tourque arm > then add another nut to hold torque arm. \this setup the torque arm covers the stripped section of axle.
B: Clean axle up and go Dropout > tabbed washer > torque arm > washer > washer > new axle nut. \ This setup washers cover stripped section.
C: I don't know.
D: Throw it in the gutter and get another.
E: Just redo the whole thread and get a new nut.
Appreciate any suggestions guys, thanks!
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Does anyone know the axle nut size on a pro 901 rear?
According to the drawing (http://www.goldenmotor.com/hubmotors/hubmotor-REAR_WHEEL.pdf) the thread is exactly the same as the Magic Pies, M14 x 1.5.
It sounds as if Jack used some of these taper seat wheel nuts:
(http://www.burtonpower.com/prodpics/large/Wheel%20Nuts%20Open.jpg)
I don't know how difficult it will be to obtain longer ones, but the more thread they have, the less likely they will be to strip the threads when tightened.
Alan
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Thanks Alan.
I'll pick up a 14 x 1.5 die tomorrow along with some new ( Preferably long ) nuts and see if I cant clean up my mess.
If that doesn't work what would be the most logical size to rethread the 14 x 1.5 to?
Thanks.
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Here's what I've done so far - The original bike had angled dropouts and a derailler that hung on the axle (a real pain), I stripped off all the spare parts and threw the frame away. I then purchased a CCM, full suspension bike with VERTICAL dropouts and a rear derailler NOT mounted on the axle. Then I cleaned up the axle with a 14mm, 1.5 pitch die and mounted the rear wheel with a rear torque arm and various spacers to get the nut off the damaged area of the axle. Various places have quoted between 32 - 50 ft/lbs of torque - I gave it 40lbs and so far it has held. If this arrangement doesn't stand the test of time, I will turn the damaged axle down to 12 mm and rethread @ 12mm and 1.5 pitch. I also have had a replacement axle on order for over a month now, hopefully it will arrive before this whole issue rears its ugly head again.
Jack
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Thanks jbc,
This is turning into a real pain in the ***
I took the motor to a few local automotive places to see if they could just clean the threads, none of them have anything that will fit, I called some local auto parts stores and same thing. Looked around hardware stores but they mostly sell complete sets and anything that has that size is well over $140+ CAN
I'm thinking maybe I'll try a drive shaft shop or something but I'll have to drive across the city for that.
Anyways thanks again for all the input everyone, I'll take jbc's advice and torque to 40lbs max once I get this resolved. I'll also update if I find any alternate solutions not mentioned to help someone else in the future.
I wish GM would give us torque specs for these wheels instead of just saying "put them on really tight" unless I missed it somewhere?
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Try a motorcycle repair shop - that's next on my list of options. The die sets come on sale periodically at Canadian Tire for about $70. You're right about that "put them on real tight" comment. This kind of "cutesy-poo" nonsense is silly and maddening.
Jack
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The biggest I found at Canadian Tire only had 12mm dies, so after spending hours locally ( to avoid driving across the city ) trying to get what I thought would be a standard die I ended up calling a buddy that works at an auto shop across town and he had a 14M 1.5 die.
We chased the threads and they cleaned up pretty good, but he didn't have any nuts he could give me. No problem, bolt supply house was only a few blocks away. So I get there and they didn't even have the bolt, nice " bolt supply house " that was.
I ended up getting 2 bolts for free at Acklands industrial so I didn't have any out of pocket expense except for my fuel and about 3 hrs of my time. Still a huge pain!
So I'm all set to put this thing back together, 40lbs max from now on. I think that should be the recommended torque cause I stripped mine at 55lbs so that's obviously way to much.
Jack, out of curiosity what did a new axle cost you?
Thanks again for all the help guys.
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Update:
Ok I'm starting to think I might have a "dud" axle. I rethreaded the stripped section, and got brand new m14 1.5 nuts. I set my torque wrench to 40lbs exactly, checked and rechecked again.
I'm not even tightening the lug up on the stripped section anymore as I moved my torque arm to the other unstripped side of the axle so I'm tightening up where the torque arm used to be on clean threads and it stripped again. I didn't even get the click to 40lbs and I can tell it's stripped. It just kept spinning and didn't get any tighter.
I stopped and set the torque arm to 30lbs and got a click, 32 click, 34 one 1/4 turn then click, 36 2 1/4 turns click, 38 3 1/4 turns no click.
So it stripped somewhere around 36 - 38 lbs
I put my other new nut tight against the stripped nut and managed to get it to 40lbs with both combined but now I know the next time I need to pull that tire I'm gonna have to deal with this again >:(
Is it possible I got a bad axle, maybe lower grade steel or something? stripping at 55lbs I can understand but 36 - 38lbs??
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I have just been Googling torque figures, and for a low grade M14 x 1.5 nut the tightening torque is 79Nm (~58ft/lbs).
But this does not take into consideration the fact that the axle thread is incomplete due to the two flats which have no thread whatsoever:
(http://www.arhservices.co.uk/GoldenMotor/Smart%20Pie/Nut.JPG)
According to my calculations, machining the flats will have actually removed almost 50% of the threaded section of the axle, therefore it would be a bit unfair to expect it to withstand the full recommended torque.
As half the thread has been removed, I would therefore suggest that the recommended torque should also be reduced by 50% too.
This would give a more realistic recommended tightening torque of just 39.5Nm, or 28.76 foot pounds.
As I mentioned in a previous post (http://goldenmotor.com/SMF/index.php?topic=3266.msg26971#msg26971), a longer (deeper) nut will be able to withstand a much greater torque without stripping because the applied load is spread over more thread.
If a 10mm deep nut strips at just over 36 foot pounds, then a 20mm deep nut should withstand just over 72 foot pounds (97.61Nm) before it strips.
I must admit that I usually tighten my axle nuts by feel, because after 40 plus years of tightening nuts and bolts, I now have a pretty good "feel" for the correct tightness of wheel nuts etc. and often have more confidence in my own judgement than the accuracy of some torque wrenches that I have used in the past. ;)
I previously used a torque wrench to check exactly how much I had tightened my axle nuts up, in order to answer a similar question (http://goldenmotor.com/SMF/index.php?topic=4494.msg25953#msg25953).
I positioned the torque wrench so it was just about level under its own weight and then slackened the nut. I then carefully retightened the nut until the released torque wrench was in the same position as it was before I slackened the axle nut.
The torque required to tighten the nut back to the same position as before was ~80Nm (59 ft/lbs).
Unfortunately, I am unable to explain why your axle threads appear to be unable to withstand the higher torque that mine are tightened to, unless they had been weakened by over-tightening them initially.
Here is my preferred tool for tightening the axle nuts, a 7/16 Whitworth ring spanner:
(http://www.arhservices.co.uk/GoldenMotor/Smart%20Pie/Tighteningaxlenut.JPG)
I would expect a standard Magic Pie to exert a maximum torque of around 50Nm through the axle, and most of this torsional force would be counteracted by the dropouts and the tabbed torque washers rather than the axle nuts.
Theoretically, the two axle nuts should be able to withstand this amount of torque without the assistance of the axle flats and torque washers etc., provided they were both tightened to at least 25Nm.
I therefore feel that the 39.5Nm, or 28.76 ft/lbs tightening torque calculated above should be more than adequate, especially when combined with the axle flats in the dropouts, torque washers and an additional torque arm.
Alan
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Thanks Bikemad:
It sounds like my 40ft/lbs should be okay. I especially like the vertical dropouts on the CCM Static bike since I feel if the wheel does want to move it will try to pound up into the dropout without any lateral movement. The torque arm should also encourage the axle to twist up into the dropout. Time will tell.
As to the cost of a new axle: Gary at GM Canada has not quoted me a price yet and the axle has not been shipped yet either. Once again, time will tell.
Jack
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Thank you Alan.
Like you I usually tighten things up by feel aswell, but I have never had a hub motor before and everything I read always just said "put them on really tight."
I even seem to remember a MP installation how to someone made that even had a poem in it, something about put them on with all your might, or it wont be a pretty sight etc etc... and it even had a picture of the guy pulling on the wrench, looking like he really was using " all his might."
I know if I used " all my might " my axle would have been stripped before I could even do the first test drive so I opted for the torque wrench but from now on if I use the torque, 36lbs max.
Anyways, I have another update on my axle. Turns out my axle and nuts are fine, after I put it back together I flipped it up on it's wheels and tried to roll it across the room but the back tire was locked up. Hmmm, I thought maybe the brake was stuck or something but it was disconnected.
I looked at the freewheel and it was tight against the dropout, so tight I couldn't even spin the wheel. I guess when I thought it was stripped, or stripping it was actually just crushing the aluminum spacer between the dropout and motor just giving the illusion of being stripped lol.
Ok I thought this sucks but no big deal I can cut a new spacer out of steel from one of my old ( on it's way to the dump ) mountain bikes. The rear of one of them had the perfect diameter metal so I pulled out my pipe cutter and cut a piece. Installed it and it crushed almost instantly.
So I searched my house and garage for anything stronger and I managed to find ( ironically enough ) an old broken torque wrench and tore into that. These new spacers are bullet proof, the steel on them is about an 8th of an inch thick so I don't think I will have that problem again. Although my pipe cutter is now going to the dump along with my old mountain bike.
I added some pics,
- My original spacer ( One bent spacer pic )
- My new steel spacer that buckled and new torque wrench spacer ( 2 spacers in pic )
Also in my search I found something that could be useful to someone and everyone should have one at home. Check out the big washer looking thing I found, it's used to hold on the blade on a skill saw and the hole fits over the axle almost perfectly and the steel is really thick and heavy. plus it has 2 holes already in it.
Maybe these could be used as torque arms or washers? Just thought I'd share. I'm a carpenter so I go through a few saws a year so I have a few of these kicking around.