MAC 500w failed at freewheel :(

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alfantastic   10 kW

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MAC 500w failed at freewheel :(

Post by alfantastic » Aug 26 2012 8:46am

After approximately 1500 miles, my MAC 500w rear hub motor has had a catastrophic failure of the side cover, which the freewheel attaches to.
I've read somewhere that other members have had problems with the metal fatiguing in this area.
I relate the failure of mine to me liking to help the motor spool up whilst on the smallest cog.
This must put a lot of torque strain on the point where the freewheel screws on to the cover.
S**t happens and I'm not going to start crying and moaning about quality etc..etc..etc..
What I do need is a solution :wink:
I still want to run a geared motor, but am now a bit wary about the MAC's freewheel side cover.
I can replace it, but I only reckon it will fail again in time. Luckily I didn't come off the bike when it failed, but I might not be so lucky next time :shock:

So I want to talk about the BMC rear motor. I hear that they are similar.
Is the construction of the BMC better than the MAC? and could I just drop in a BMC as a direct replacement to the MAC?
I want to keep Cellman's 9 fet 30A controller, as it is CADP compatible and it's programmed perfectly for me.
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dogman dan   100 GW

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Re: MAC 500w failed at freewheel :(

Post by dogman dan » Aug 26 2012 12:37pm

My impression is that it's a luck of the draw thing mostly.

Might help to not pedal till you are going 7-10 mph. I started doing that beacause I was skipping chain on 14 t cogs unless I had a brand new on on the bike. I always did pedal hard off a stop, and it took a while to get out of that habit.

But your next cover might just be tons stronger than the last one, as it can be with cast aluminum stuff. It does seem though, like the occasional broken cover is a Mac thing, while I don't recall many if any at all reports of the same thing on 9c types. I remember it was sort of common on 5300 clytes though.

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Re: MAC 500w failed at freewheel :(

Post by neptronix » Aug 26 2012 12:41pm

Freewheel side cover failures are pretty common with hub motors. I've managed to destroy mine once on my MAC. It's happened on crystalytes, BMCs and bafangs as well.

You are right in that the high gear is likely the cause :(
How old is this motor? I believe there have been 2 different freewheel cover revisions. There may be a new revision of the freewheel cover available as a replacement part.

I'm not sure if the BMC is constructed better, the only advantage i know of is that the water seals. A lot of the parts are the same or functionally and physically identical. The side cover design is different, but the freewheel thread side cover is close enough in design that it may have the same problem. Not sure.
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My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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Re: MAC 500w failed at freewheel :(

Post by alfantastic » Aug 26 2012 12:58pm

I bought it within the last six months. It has the new upgraded composite gears, so assume it has the latest side covers???
It's all a learning curve, so once repaired, will use less pedal assistance and let the motor do most of the work.
I'm not at all fussed about the failure, but it was pretty unnerving when it went, as my driving foot shot to the ground like a bullet and I could have quite easily lost control.
Also, the bike was unrideable due to too much wheel movement for powered drive, and human power was obviously no go too :roll:
No more off seat pedaling for me.

The freewheel side cover should be manufactured in steel, as I can see this as a potential problem with all hub motors.

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dogman dan   100 GW

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Re: MAC 500w failed at freewheel :(

Post by dogman dan » Aug 26 2012 1:05pm

At least better alloy alumimun would be nice, rather than random mix formula. One day they pour old window frames, another day beer cans. How many regular alloy bike hubs twist in half? Different design of course, quite possibly not a cast part.
Last edited by dogman dan on Aug 26 2012 1:10pm, edited 1 time in total.

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Re: MAC 500w failed at freewheel :(

Post by neptronix » Aug 26 2012 1:07pm

OK, that sucks. I think you have the newest freewheel cover :(
I know what you mean in that the motor becomes useless, as it did happen to me once :/

OK, now the truth comes out. You were standing on the pedals at the highest gear, lol. Yeah, that's a no no. That would break some freewheel covers on a lot of hubs ;)

Yeah, they should be designed stronger, for sure. The only hub motor i can think of that doesn't consistently have this issue is the MXUS / 9C style motors.
alfantastic wrote:I bought it within the last six months. It has the new upgraded composite gears, so assume it has the latest side covers???
It's all a learning curve, so once repaired, will use less pedal assistance and let the motor do most of the work.
I'm not at all fussed about the failure, but it was pretty unnerving when it went, as my driving foot shot to the ground like a bullet and I could have quite easily lost control.
Also, the bike was unrideable due to too much wheel movement for powered drive, and human power was obviously no go too :roll:
No more off seat pedaling for me.

The freewheel side cover should be manufactured in steel, as I can see this as a potential problem with all hub motors.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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dogman dan   100 GW

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Re: MAC 500w failed at freewheel :(

Post by dogman dan » Aug 26 2012 1:12pm

Yeah, I stand the pedals in high gear all the time with muxus, 9c stuff. Couldn't break one with a 56 tooth chainring.

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Re: MAC 500w failed at freewheel :(

Post by alfantastic » Aug 26 2012 1:24pm

neptronix wrote: OK, now the truth comes out. You were standing on the pedals at the highest gear, lol. Yeah, that's a no no. That would break some freewheel covers on a lot of hubs ;)
Oh yeah, I admit total liability for this little mishap :oops:
It's good to let the community know what happens when these things break.
I was on an off road track, so the ensuing wobble of man and machine didn't cause any problems, but if one was riding in traffic.... Ewwwwwww :shock:

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Re: MAC 500w failed at freewheel :(

Post by Wurly » Aug 26 2012 2:52pm

When you get a replacement cover, you might want to try this idea by mxer. It's a sealed bearing and a machined spacer. The idea is the bearing takes the load of the freewheel rather than the cover. It's a cheap and easy solution. I have done the same this with my BPM hubs.
http://www.endless-sphere.com/forums/vi ... 7&start=15

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Re: MAC 500w failed at freewheel :(

Post by d8veh » Aug 26 2012 5:35pm

Sorry to hear of your problem. I thought that everyone recommends MACs because spare parts are availablr. Perhaps someone would be so kind as to point you to the source of a new cover.

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Re: MAC 500w failed at freewheel :(

Post by docnjoj » Aug 26 2012 6:24pm

That outboard bearing seems like a good fix. I only ride a recumbent but I can still put a fair amount of force using the seat back. I have only destroyed one old Crystalite brushed motor by breaking off the freewheel. I can't break a 9C even with maximum force but I also use 155mm pedals. That could help! Yeah I'm old but I use to have a 36" vertical leap playing basketball. Once had good legs.
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Re: MAC 500w failed at freewheel :(

Post by alfantastic » Aug 26 2012 11:00pm

d8veh wrote:Sorry to hear of your problem. I thought that everyone recommends MACs because spare parts are availablr. Perhaps someone would be so kind as to point you to the source of a new cover.
I can get an original replacement part no problem. It seems a shame that I will have to change my riding style to minimize it happening again.

I have spotted this, but unsure of the vendor or whether it is the freewheel side cover (not gonna trust picture):

http://shop.efairy.eu/E-Bike-Hub-Motor- ... anguage=en

Stainless steel, now we're talking :D
I've e-mailed them to find out the details.
If it is the correct part, then I'll order one and be the guinea pig :wink:
Expensive I know, but who said electric biking was gonna be a cheap hobby :shock:

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Re: MAC 500w failed at freewheel :(

Post by teklektik » Aug 26 2012 11:28pm

The BMC sidecover has a threaded steel insert for the freewheel. I understand from Ilia at ebikessf that the newest MAC side covers he is getting also now use the same approach instead of the older all aluminum design. He carries both MACs and BMCs and sources gear clusters for both - not sure about cover plates. He ships quick and has great support - worth checking.
Wurly wrote:When you get a replacement cover, you might want to try this idea by mxer. ... The idea is the bearing takes the load of the freewheel rather than the cover. ... I have done the same this with my BPM hubs.
I always wondered how folks removed the freewheel once the bearing was in there... it kind of prevents using the standard splined freewheel tool.
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Re: MAC 500w failed at freewheel :(

Post by veloman » Aug 27 2012 12:00am

I am not certain that you have the NEW Mac freewheel cover. Your hub looks gray which is the older weak style which has this problem a LOT. My gray cover is cracking but didn't fail. Cellman got me a new black cover. If you tap it with your fingernail and do the same with the old gray one, they sound different.

Are we sure that the new black Macs are not steel? I should have weighed them to compare. I hope my black one doesn't fail as I sometimes sprint like hell on it. At least I have my 9c as a back up if it happens. Right now my gf is riding the replacement cover on my old gray Mac.

Someone with some machining capabilities could make us steel covers.....
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Re: MAC 500w failed at freewheel :(

Post by neptronix » Aug 27 2012 12:03am

the Mac sidecover also has a stainless steel insert.
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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Re: MAC 500w failed at freewheel :(

Post by veloman » Aug 27 2012 12:04am

neptronix wrote:the Mac sidecover also has a stainless steel insert.

How far into the cover does it go? I think I remember seeing some coloring/marking on the inside in that area.
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Re: MAC 500w failed at freewheel :(

Post by neptronix » Aug 27 2012 4:18am

Good question. I'm one revision away from the newest style of side cover, so what i have to say may not be relevant here.

My last one seemed to have the freewheel insert going fully through the sidecover.

http://endless-sphere.com/forums/viewto ... &start=105

^-- see the gore here!
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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Re: MAC 500w failed at freewheel :(

Post by alfantastic » Aug 27 2012 6:47am

veloman wrote:I am not certain that you have the NEW Mac freewheel cover. Your hub looks gray which is the older weak style which has this problem a LOT. My gray cover is cracking but didn't fail. Cellman got me a new black cover. If you tap it with your fingernail and do the same with the old gray one, they sound different.
The hub is actually all black, that's just the dusty crud on it that's making it look gray.
Thought about buying that stainless steel side cover from that link that I provided, but can actually buy a dozen covers from Paul for the same price.
So gone ahead and ordered a couple from him. 30 minute job to replace if the bugger goes again :wink:

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Re: MAC 500w failed at freewheel :(

Post by veloman » Aug 27 2012 12:25pm

Damn, well I think we should all send pics of our damaged side covers to Mac and tell them to make steel sidecovers on the drive side. I can't believe that stainless steel covers cost 5x more than aluminum.... maybe it's someone else manufacturing them.

So it looks like I'll be riding the 9c when I want to hammer on the pedals.......


I would really love it if they made the hub with a cassette body instead of freewheel threads. I can get used cassettes for next to nothing around here, and any gear ratio is easy. Freewheels are a LOT heavier too.
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Re: MAC 500w failed at freewheel :(

Post by alfantastic » Aug 27 2012 1:07pm

veloman wrote:Damn, well I think we should all send pics of our damaged side covers to Mac and tell them to make steel sidecovers on the drive side. I can't believe that stainless steel covers cost 5x more than aluminum.... maybe it's someone else manufacturing them.
Here's that link again for anyone interested in the steel cover. Think you may be right in that they are manufacturing these themselves and not MAC:

http://shop.efairy.eu/E-Bike-Hub-Motor- ... anguage=en

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Re: MAC 500w failed at freewheel :(

Post by Wurly » Aug 27 2012 2:08pm

teklektik wrote:
Wurly wrote:When you get a replacement cover, you might want to try this idea by mxer. ... The idea is the bearing takes the load of the freewheel rather than the cover. ... I have done the same this with my BPM hubs.
I always wondered how folks removed the freewheel once the bearing was in there... it kind of prevents using the standard splined freewheel tool.
I also was concerned about that, so i made sure the bearing and the spacer fitted without being forced into place. If i have to remove the freewheel i simply undo the cover screws, gently lever off and tap the spacer and bearing away from the inside of the cover. Then you can remove the freewheel with the removal tool.

I wish i could get a stainless steel cover for my BPM.

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Re: MAC 500w failed at freewheel :(

Post by veloman » Aug 27 2012 2:24pm

Wurly wrote: I wish i could get a stainless steel cover for my BPM.

Same place:
http://shop.efairy.eu/E-Bike-Hub-Motor- ... l::70.html
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Re: MAC 500w failed at freewheel :(

Post by alfantastic » Aug 28 2012 8:53am

Is there any way of visually checking for potential failure of this part, or do they go without warning?
I do feel that it just gave way and I could not have pre-empted it.
One of the reasons I never went for a front hub on aluminium forks :shock:

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Re: MAC 500w failed at freewheel :(

Post by veloman » Aug 28 2012 12:23pm

Yes, my gray Mac side cover is cracked in a circle around the freewheel threads but still completely intact and rideable (been riding it knowingly a fair bit, until now I got the replacement). So you can check your cover every few weeks, but it's still no guarantee that it won't just break without cracking first. I'm sure a lot has to do with how hard you are pedaling from a stop.
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Re: MAC 500w failed at freewheel :(

Post by neptronix » Aug 28 2012 12:47pm

I was not able to predict my failure :/
Efficiency is everything :bolt:

My first major build: 1.6kW 8T MAC motor on a Trek 4500.
The new all-arounder: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: 20" eZee on a Cannondale Semi Recumbent.
Whipper-snapper: ? on a lightweight BikeE Semi Recumbent

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