Mating hub motor to fat tire mongoose dolomite

[caleb]

Hi All,

I am trying to adapt a new 1000 w 48 v hub motor to a new fat bike. I got a new Mongoose Dolomite Bike and a new motor for it. Getting a REAR 700C bikeling wheel, which had the 135mm spacing needed for the fat front fork. Looking at the hub motor, it has 12ga spokes. The OEM bike came with 14 ga spokes. Took it to bike shop to have him lace the wheel to hub, and he has some issues that halted the start of the project. Looking for other examples or input.

Issues:
Mongoose has 14 ga spokes, new hub motor has 12 ga spokes. Expect need to drill out rim to 12ga spoke nipples.
need shorter 12 ga spokes. anywhere I can buy custom lengths spokes that are already threaded 12ga?

Or alternatives for easier way to get 1000 watt hub motor adapted to a walgoose fat bike?

thanks

 

[wesnewell]

I've heard the rims on those aren't the greatest. You might consider using one of these. I'm pretty sure they come with 12G holes, but double check.
http://www.niagaracycle.com/categories/weinmann-dhl101-alloy-rim-26-x-4-0-36h-black
There are lot's of places to get custom length 12g spokes, even ebay.
http://www.ebikessf.com/catalog/41
Now, can you tell me the dropout widths? I've been thinking of buying one of these.

 

[caleb]

Thanks for links!

The front dropout is 135mm and fits a REAR hub motor no problem. The rear dropout is around 170mm, but I haven't taken the rear wheel off to measure exactly. The bike is pretty neat. I waited until price dropped back to $250, sold my beast single speed, and have been pedaling this Dolomite a few miles so far. I did 12 miles roundtrip to the beach including over a mile pedaling down the beach. very fun!

I bought this hub motor and it fits the front fork http://www.ebay.com/itm/141355018939?_trksid=p2059210.m2749.l2648&var=440494682141&ssPageName=STRK%3AMEBIDX%3AIT

 

[Drunkskunk]

Steer clear of 12g spokes. They are simply too thick to do the job. While the motor came with 12, they are likely softer low quality spokes, and not even comparable in strength to a thinner 14g.

14 gauge is thick enough for DH bikes flying off ski jumps and dropping of cliffs, so it's more than enough to handle an Ebike, yet still flexible enough to do it's job of spreading the load. Depending on the motor holes, you may want straight 14g, or single butted 13/14. JRH is a good source for them, but any bike shop should be able to get straight 14g spokes.

The Weinmann rim is an improvement over the stock rim, but not much. ChoppersUS rims are about double the money, but much better quality. If you plan to put much power through that wheel, or hit much speed, you may want to further the upgrade.

 

[wesnewell]

Thanks for the dropout info. I'm thinking of putting a 3kw or 5kw motor on the rear with a 21" motorcycle wheel, Should be plenty of room for it and a 7 speed freewheel.

 

[wesnewell]

Steer clear of 12g spokes. They are simply too thick to do the job. While the motor came with 12, they are likely softer low quality spokes, and not even comparable in strength to a thinner 14g..

Yeah, aren't all those people that make motorcycle wheels and spoked rims for sports cars really stupid to use such large spokes. They should all be using 14g spokes. I just can't understand why I haven't broken a spoke in over 2 years of using SS 12G spokes, since they are so much weaker than 14G spokes. :lol:

 

[cal3thousand]

Sure 12G spokes might work OK in some bike applications. But 14G is still the better choice for bike applications. Look at it this way, your butt may be fine with paper towels and napkins, but once you try real 2-ply toilet paper, you won't frock with the rest.

Whatever your tushes preference, the point still stands that a bike shop will not have the tools to get you 12G spokes, if and, when they do break. They also will not work on truing your wheel.

So, your choice. But be prepared to DIY if going 12G. My first motor was a poorly built wheel (I did not build it) using 12G spokes that popped and broke every other ride. The worst part was being a noob at the time, and getting NOWHERE with local bike shops. You'll also have to have different spoke tools for your front and rear wheels. I have yet to see the benefits of a 12G spoked bicycle wheel. ......Maybe if you're using a Cromotor Mammoth

 

[windtrader]

Really?

12 gauge spokes are not stronger and more durable on a bike? All my reading had me putting 12g spokes on my build list. Wheels from worksman for example are 12g and I never heard anyone say those wheels had any durability issues. Maybe there are not many ebikes built off this so less feedback here.

What is the rationale that a thinner spoke would be stronger than a similarly constructed one of a lower gauge (thicker)? Does added flex allow for a overall "stronger" wheel, one that absorbs more shock without breaking?

 

[cal3thousand]

Really?

12 gauge spokes are not stronger and more durable on a bike? All my reading had me putting 12g spokes on my build list. Wheels from worksman for example are 12g and I never heard anyone say those wheels had any durability issues. Maybe there are not many ebikes built off this so less feedback here.

What is the rationale that a thinner spoke would be stronger than a similarly constructed one of a lower gauge (thicker)? Does added flex allow for a overall "stronger" wheel, one that absorbs more shock without breaking?

a spoked wheel works opposite of most peoples intuition. They hold the wheel together in tension with spokes stretched to an elastic point. At no point do you want any single spoke to come out of tension and into compression.

With 12G spokes, they require more tension to properly stretch, thus making them more difficult to keep in even tension. Not that they can't build strong wheels, but you are adding unneeded (in bike applications) work since 12G are not in the normal bike realm (no bike shop support).

 

[wesnewell]

A thinner one is not stronger. The cause of most broken spokes is improper installation. Namely not tensioned enough. Thinner spokes reduce weight and drag a little and would be preferred if you were in a pedal race. But so would a fiber frame. I don't care what size spokes you use, if you don't install them properly they will break.

 

[cal3thousand]

A thinner one is not stronger. The cause of most broken spokes is improper installation. Namely not tensioned enough. Thinner spokes reduce weight and drag a little and would be preferred if you were in a pedal race. But so would a fiber frame. I don't care what size spokes you use, if you don't install them properly they will break.

And I contend that 12G spokes are tougher to install correctly in a bicycle wheel as opposed to 14G. Also tougher to find support when needed.

 

[windtrader]

And I contend that 12G spokes are tougher to install correctly in a bicycle wheel as opposed to 14G. Also tougher to find support when needed.

OK. That makes perfect sense and I thought this may be the rationale. But this goes with any wheel building. It is an art to get right and many broken spoke problems are most likely happening to those who DIY or go to some LBC where they have someone building and truing wheels who does not have sufficient expertise.

So the lesson to add to the builder's checklist is make sure, if using 12 gauge spokes, to have them built properly by an experienced 12g wheel builder.

 

[wesnewell]

Experience doesn't make up for stupidity. I'd never done it before, but I laced my own. Took a while to get the proper tension. I started way too loose. But that was almost 2 years ago and I haven't broken a spoke yet. And most already know I'm on the heavy side.

 

[Chalo]

If you ask, you can often get rim manufacturers to specify a per-spoke tension limit. Some of them specify 100kgf. I like Alex rims, and one of the things I like about them is that they specify a 140kgf per-spoke limit.

Well, 140kgf isn't going to stretch a 12ga spoke enough to keep it tight. You can crank it up even more, at the risk of damaging the rim, and contrary to the manufacturer's recommendations. But I am not aware of a spoke tensiometer that works with spokes thicker than 13ga anyway.

 

[dogman dan]

Definitely true about getting it right with 12g spokes. We need real ebike rims we can torque it down on. And nipples that can stand that. Cheap mismatched stuff limits you badly.

My approach has been to run a somewhat looser spoke tension. The wheel definitely creaks but not a lot. The key is not having any of the spokes tighter than the other. This can only be done with an undamaged, straight rim. Once you bend a rim, you end up with one side all tight and the other all loose. That's going to start busting spokes for sure.

 

[bowlofsalad]

If you ask, you can often get rim manufacturers to specify a per-spoke tension limit. Some of them specify 100kgf. I like Alex rims, and one of the things I like about them is that they specify a 140kgf per-spoke limit.

Well, 140kgf isn't going to stretch a 12ga spoke enough to keep it tight. You can crank it up even more, at the risk of damaging the rim, and contrary to the manufacturer's recommendations. But I am not aware of a spoke tensiometer that works with spokes thicker than 13ga anyway.

I think the common practice is to use a torque wrench instead of a tensiometer in wheels that might be classified as motorcycle wheels.

http://www.amazon.com/gp/product/B004MSMAPY/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B004MSMAPY&linkCode=as2&tag=xbnijgbr-20&linkId=ALO7CF3CWTSBHXWV An example of one.

 

[Chalo]

I think the common practice is to use a torque wrench instead of a tensiometer in wheels that might be classified as motorcycle wheels.

http://www.amazon.com/Motorcycle-Wheel-Torque-Wrench-Universal/dp/B004MSMAPY An example of one.

That's one way to do it, but the torque:tension ratio can vary by a factor of two between a dry fastener and a greased one. It can vary by another 2:1 or more between a greased fastener and a moly lubed one, or a dry clean one and a dry cruddy one. And of course any of the above can vary by an infinite amount from the torque:tension ratio of a spoke that's rusted solid onto its nipple. That definitely limits the absolute precision of a tension measurement predicated on torque.

Bicycle spoke tensiometers operate by flexing a spoke between three anvils and measuring the amount of deflection. This method has good fidelity, but depends on the spokes being thin enough that the effect of tension is greater than the effect of beam stiffness.