MXUS 3K Turbo Lacing

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Oct 17, 2020
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I've been having a real sticky time figuring out how to get my MXUS 3K motors laced into wheels, and I'm primarily stuck with spoke length. Has anyone ever done a 16" moped rim with the MXUS 3K that could tell me what he has used in terms of spoke length/rim? I'm also open to some kind of 20" BMX rim, but I'm a little fuzzier on the specifics of how I would drill out the holes in that rim. I've had a peruse through all the moped rim threads here, but as JRH doesn't seem to make rims anymore, there's a dearth of resources, and I hate randomly guessing. Thanks! :bolt:
 
Remember that moped rims have angled nipple rests while BMX wont. You'll have to radial lace the 20" BMX rim, good news is https://ebikes.ca/tools/spoke-calc.html has the info on mxus 45H aka 3kw in the pull down written as MXUS XF-40-45H hopefully they'll have your rim to, otherwise just input rim #'s into calculator. With Alex DM24 a 20" the spoke length would be 95 and 96mm for a 1X cross pattern which wouldnt be recommended but 80 and 81mm for 0X or radial pattern.

I do not know how you'd go about getting the ERD for a moped rim, unless its already given to you and even then you should double check the ERD. I was off by a bit on my last 19x1.40 moped rim ERD measurement.

https://ebikes.ca/tools/spoke-calc.html?hub=MX_45&pair=false&rim=20DM&cross=0
 
Thanks for the informative response! I didn't assume that the 3K was in Grin's calculator - that's useful to know. My worry with BMX rim use is the spoke gauge needed for the motor. It's 10G, is it not? How would I get spokes that both fit in the rim and in the motor?
 
I've never found a 16" moped rim wide enough for my desires. So I'm using what were originally the old Zero Motorcycle rims, off what was probably the first version of it, which are basically heavy duty wide BMX rims with nipple reinforcements. Some rims taht were suggested as replacements are over in this thread, when I ran out of these.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=109053&hilit=rim%2A
but they were all on the expensive side (because of shipping, mostly).


You can use spoke washers, or you can drill the spoke flange with smaller holes like I did (which has worked fine even on my heavy-cargo-hauler trike SB Cruiser...the internals of the motor have had problems, and the axles have broken, and the rims have been crushed by potholes, but the spokes and flanges and nipples and nipple holes are all still fine. (even after relacing the same spokes into a new rim after the first crushed rim). The left wheel has been working for over three years; the right for almost three (it's off now because the motor itself failed internally, probably windings again).

https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1362771&hilit=mxus+drill#p1362771

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Another relevant post for you
https://endless-sphere.com/forums/viewtopic.php?f=3&t=96459&p=1447410&hilit=drill+mxus#p1452205
Chalo said:
hias9 said:
I am using 13ga Sapim spokes for this motor, and maybe 13/14 butted spokes for the next one.

Would you lace it with the spoke elbow to the outside for all spokes or alternating?

Not alternating, and not all elbows-out or elbows-in for a rear hub. Rear hub motors and most disc brake compatible front hub motors have asymmetrical flange spacing, which makes for unequal tension-- sometimes ridiculously unequal-- and a weak wheel. Lace the spokes all outside the flange that's closer to the midpoint of the axle, and all inside the flange that's farther out. That helps compensate for the asymmetrical flange spacing.

Alternating spokes inside/outside the flange is necessary for multi-cross patterns that would cross too near to the flange, but for radial and cross-1 lacing, you might as well take advantage of the bracing angle options afforded by putting the spokes all on one side of the flange.

If the hub has symmetrically spaced flanges, then it's usually best to lace all the spokes elbows-out. But when the hub diameter is close to the rim diameter, it becomes necessary to lace all the spokes elbows-in to moderate the angle at which they enter the rim holes.
 
Polyax washers are good.

13g are the biggest you'd want to go, theres probably a reason why Grin does not sell 12g spokes for bicycle rims. The reason is the spokes need to stretch along with the rim, that flexibility is what you want otherwise you start cracking rims with 10g.

https://www.bikeraceinfo.com/tech/bicycle-spokes-things-you-never-knew.html
the lighter spokes are stronger because they stretch a little better (and have been hardened more).
 
I appreciate all the info, guys. I'm not sure I would need quite so wide a rim - I'm only going for 2.5" and 2.75" wide moped tyres (Mitas MC2 and similar). There are definitely moped rims of 1.6" width or so that would work. The points about spokes are well-taken. I just find that finding anything reasonably compatible is incredibly frustrating.
 
Excaliburke said:
I appreciate all the info, guys. I'm not sure I would need quite so wide a rim - I'm only going for 2.5" and 2.75" wide moped tyres (Mitas MC2 and similar). There are definitely moped rims of 1.6" width or so that would work. The points about spokes are well-taken. I just find that finding anything reasonably compatible is incredibly frustrating.
If you don't mind buying a whole wheel to get the rim, there's always places like treatland.tv ("famous" moped parts webstore) and the like.

Regarding width, I'm using the Shinko SR741 2.25" on that 50mm rim, and it works well on it. I'd rather use the 2.5 or 3" which would also work on it but won't fit inflated inside my fender frames. :lol: I'd have to rebuild the cargo area of the trike, and if I'm doing that, there's so many other changes I'd make at the same time I might as well build a new trike...so I will do just that, and am now collecting parts for the new version, waiting to hear back from the first place on pedicab wheel parts, axles, forks, and stuff like that, since I'll be using much larger (29") wheels on front and rear this time, as it's an unsuspended heavy cargo trike and our roads are...less than perfect, shall we say. ;)


Anyway, you can use a narrower rim with those tires if you like; it'll make the profile "taller" / rounder, with a little less contact patch than a wider rim causes. I think it'll also hold a little less air than the wider rim.
 
Ah, gotcha. Yeah, I'm also doing some light cargo endeavors! I think I was responding to the fact that the other thread you linked was suggesting a 65mm wide fat bike rim, which would seem altogether too wide.
 
Excaliburke said:
Ah, gotcha. Yeah, I'm also doing some light cargo endeavors! I think I was responding to the fact that the other thread you linked was suggesting a 65mm wide fat bike rim, which would seem altogether too wide.
It depends on what you're after. Since I was looking for *at least* 50mm wide rims, then for me those would be good. Since you want narrower ones, then those specific ones aren't, but if you look around at sites that carry those, they will also carry narrower ones. :)


FWIW, if you don't have suspension, then as long as your frame accomodates the inflated tire size, you may be better off with a wider rim and tire, to get more air in there to cushion your ride. The heavier the bike or trike is, especially over the smaller wheels, the harder it is on them. The more air in the tire, the more the tire takes that pounding and the less the wheel (and bike/trike) does.

This is one reason I am going for 29" wheels on the new one, instead of 26" front and 20" (22"ish actual with the moped tires), because the 26" is fairly good even with a "normal" (CST City) tire, but the 20" even with the biggest tires I can fit back there suck when I am on bumpy or potholey roads. (evertyhing from just being shaken up to jolted all the way to broken axles and crushed rims).
 
I prefer the smaller tyres currently. :wink: I can find 1.6" moped rims which would seem to fit the bill, but the accursed spoke lengths is just destroying my brain. There's no good way to actually figure the thing out. :cry: Angled spoke holes I think is the main issue, and lack of ERD measurement.
 
The grin spoke calculator shows how to measure ERD, etc., to ensure you get the right measurement.

The angled holes may complicate things a bit, because the dimple is recessed and will "shorten" the spoke needed a bit. Sites that sell motorcycle spokes may have help on that part--I've never figured out a MC rim spoke setup so I don't know the details. :(
 
I've just recieved an [Edit 26"] MXUS 3K V3 from this ebay-er and he also sells a 16" version https://www.ebay.co.uk/itm/16-MXUS-3K-Turbo-v3-Motor-3kw-3000w-6000w-peak-ebike-dd-hub-motor/133621899748?hash=item1f1c7c61e4:g:cxsAAOSwBLNf618O
He sells spokes and rims as well as built wheels so he might be able to help
Not sure about the strange configuration of spokes he sent on mine. 10Ga with [edit cross laced ] alternating long and short spokes - maybe 15/20mm different in length. If anyone knows why I'd be interested
 
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BobBob said:
I've just recieved a MXUS 3K V3 from this ebay-er and he sells a 16" version https://www.ebay.co.uk/itm/16-MXUS-3K-Turbo-v3-Motor-3kw-3000w-6000w-peak-ebike-dd-hub-motor/133621899748?hash=item1f1c7c61e4:g:cxsAAOSwBLNf618O
He sells spokes and rims as well as built wheels
Not sure about the strange configuration of spokes he sent on mine. 10Ga with alternating long and short spokes - maybe 15/20mm different in length. If anyone knows why I'd be interested
You'd have to post a picture, becuase I don't see how you could radially lace a motor with different lengths of spokes (unless one side has shorter ones to dish the rim drastically to that side). Attached image of wheel from the page you linked, which shows a radial lacing to a 16" motorcycle wheel.
s-l1600.jpg


As a side note, this motor laces up radially in a 20" bicycle (16" MC) wheel perfectly fine (if you either use spoke washers, or drill a new set of smaller holes in the flanges like i did) with 13/14 single-butted spokes. Except for the repeated broken axles due to poor axle design and materials, it's worked fine for two of these motors (different generations and windings) on the two rear wheels of the SB Cruiser trike, with up to close to half a ton of weight on them when I have large cargo loads. I've bent rims on potholes, but haven't had spokes come loose, etc.
dsc08103.jpgdsc07690.jpg
 
amberwolf said:
BobBob said:
I've just recieved a [Edit - 26"] MXUS 3K V3 from this ebay-er and he sells a 16" version https://www.ebay.co.uk/itm/16-MXUS-3K-Turbo-v3-Motor-3kw-3000w-6000w-peak-ebike-dd-hub-motor/133621899748?hash=item1f1c7c61e4:g:cxsAAOSwBLNf618O
Not sure about the strange configuration of spokes he sent on mine. 10Ga with alternating long and short spokes - maybe 15/20mm different in length. If anyone knows why I'd be interested
You'd have to post a picture, becuase I don't see how you could radially lace a motor with different lengths of spokes (unless one side has shorter ones to dish the rim drastically to that side).
Sorry, I didn't say, mine's a 26" cross laced with the spokes that accellerate the wheel measuring 137mm 5.4" and the "braking" spokes being 152mm 6" hub to nipple
More discussion in my build thread as I don't want to hijack this thread https://endless-sphere.com/forums/viewtopic.php?f=6&t=110840&start=25#p1649035
Top View.jpg
Angled.jpg
 
Thoughts anyone?
Triangles of forces show that due to one set of spokes being 15mm longer than the other, there will be 1.8 X more the tension on the more radial ones.

To get enough tension on the more angled spokes, the shorter more radial ones would be over tight.
Any better ideas than the guy lacing was an idiot or ran out of the correct length spokes?

I'm thinking of asking the seller to just send me more spokes and re- lace it
I reckon I could do a better job of angling the spokes while I'm at it but haven't laced a wheel before, have trued buckled ones though

2D projection of CAD of measured wheel with equal rotational forces showing 1.8X length equivalent to tension
Spoke Stress.png
 
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