20 inch rim for motor and 12G spoke holes ?
- Thread starter iperov
- Start date
oops
found various links on taobao
http://item.taobao.com/item.htm?id=13582652577&ali_trackid=2:mm_14507416_2297358_8935934:1353748518_4k9_2093728293
http://item.taobao.com/item.htm?id=7360651472&ali_trackid=2:mm_14507416_2297358_8935934:1353748886_4k2_2019106465
http://item.taobao.com/item.htm?id=14233208043&ali_trackid=2:mm_14507416_2297358_8935934:1353749050_3k7_2066489831
so, good topic for google searchers
found various links on taobao
http://item.taobao.com/item.htm?id=13582652577&ali_trackid=2:mm_14507416_2297358_8935934:1353748518_4k9_2093728293
http://item.taobao.com/item.htm?id=7360651472&ali_trackid=2:mm_14507416_2297358_8935934:1353748886_4k2_2019106465
http://item.taobao.com/item.htm?id=14233208043&ali_trackid=2:mm_14507416_2297358_8935934:1353749050_3k7_2066489831
so, good topic for google searchers
Chalo
100 TW
iperov said:
Most 20" rims don't have eyelets on the spoke holes, so you can just drill them to whatever size you like.
Spokes that thick don't help, though, and they make a wheel that needs more frequent maintenance and is quicker to crack at the rim holes. 14ga (2.0mm) spokes are more than strong enough if you use good quality spokes like DT Swiss or Sapim, stress relieve the wheel when building it, and get it good and tight. The strength of the wheel is in the rim, not the spokes.
The widely available Alex DM24 is a very good strong rim for the money, but most versions of it have eyelets. That's a good thing, if you use normal 2.0mm spokes.
Chalo
Trust me when i say that for 20" rims, 14" spokes are absolutely fine.
You want a little spoke flex, and given that the rim diameter is much smaller than a 26", 14 gauge is appropriate for very high power chain driven builds. I believe that Liveforphysics' deathbike ( >30kW ) is laced up with 14 gauge spokes.
You want a little spoke flex, and given that the rim diameter is much smaller than a 26", 14 gauge is appropriate for very high power chain driven builds. I believe that Liveforphysics' deathbike ( >30kW ) is laced up with 14 gauge spokes.
At the risk of incurring the wrath of Chalo who reasonably opines that motorbike rims are overkill, here are pictures of the 1.60 internally wide Pro Wheel 16" rim I use with with a HT3525 hub.
http://www.prowheelracing.com/yamaha-play-bike-rear-rim-1-60-x-16-silver/
The rim weighs 2.4" and is single cross laced with 12Ga Phil Wood spokes (Ilia Brouk sold me the hub and laced it into the rim which I dropped-shipped top him in San Francisco at ebikessf.com from Pro-Wheel in Washington State). Note the angled holes which permitted the cross lacing.The hub costs $94 plus shipping.
As I learned on ES, most 20" BMX tires will fit onto a 16" motorbike rim. I include a picture of the heaviest duty BMX tire I could find: the Subrosa Grave Digger which is nominally a 20" x 2.3" tire weighing 29+ oz. On this rim it is 2.52" at the widest and has a diameter of 20.5"
View attachment 2
Sorry: The hub in rim photo won't open inline so you'll have to download it.
http://www.prowheelracing.com/yamaha-play-bike-rear-rim-1-60-x-16-silver/
The rim weighs 2.4" and is single cross laced with 12Ga Phil Wood spokes (Ilia Brouk sold me the hub and laced it into the rim which I dropped-shipped top him in San Francisco at ebikessf.com from Pro-Wheel in Washington State). Note the angled holes which permitted the cross lacing.The hub costs $94 plus shipping.
As I learned on ES, most 20" BMX tires will fit onto a 16" motorbike rim. I include a picture of the heaviest duty BMX tire I could find: the Subrosa Grave Digger which is nominally a 20" x 2.3" tire weighing 29+ oz. On this rim it is 2.52" at the widest and has a diameter of 20.5"
View attachment 2Sorry: The hub in rim photo won't open inline so you'll have to download it.
Chalo
100 TW
Lemlux said:
There's not a thing wrong with MC rims as long as they are part of a balanced system. Big heavy rims go with big strong hubs, thick spokes, and high spoke tension. Waste and inefficiency come in when a rim and spokes intended for a 400 pound, 50hp motorbike are laced to bicycle hubs. It's like putting tractor wheels on a Volkswagen-- it doesn't make the VW into a capable tractor, but it does spoil its ability to exhibit the basic virtues of a VW.
I think your wheel is in balance with itself, but is not matched to the bike it's attached to. Any operating conditions that would work the wheel anywhere near its limits would destroy most of the rest of the bike. (In which case, I suppose, the wheel could be carried over intact to a more robust bike.)
I have no problem with my hub wheel assembly being the strongest part of my bike.
In fact, I consciously made the strength/weight tradeoff. A Velocity Psycho 20" bicycle rim, for example, weighs 1.3# compared to the 2.4" of the Pro-Wheel rim. A 1.1# weight penalty (perhaps 1.2# including 12 Ga spokes rather than 14 Ga spokes) seems minimal to me.
I routinely accelerate off the line at up to 3450 watts which generates max torque of of about 120 pounds of thrust. I frequently use regen braking which, at speed, can kick in instantaneously at about 1500 watts. I like having a strong wheel in back in heavy chromoly dropouts with a thick chromoly torque plate all securely mounted using Nordlock washers.
If my 1.8# tire wears out as quickly as Nep and others caution, I'll then make the greater (4# - 1.8#) = 2.2# tradeoff (double my current rim weight tradeoff) of moving to a DOT tire.
My tradeoff decision is reinforced when I read concerns about 20" drive wheel rim / spoke maintenance issues in threads like this current thread on pizza delivery bikes:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=45841
In fact, I consciously made the strength/weight tradeoff. A Velocity Psycho 20" bicycle rim, for example, weighs 1.3# compared to the 2.4" of the Pro-Wheel rim. A 1.1# weight penalty (perhaps 1.2# including 12 Ga spokes rather than 14 Ga spokes) seems minimal to me.
I routinely accelerate off the line at up to 3450 watts which generates max torque of of about 120 pounds of thrust. I frequently use regen braking which, at speed, can kick in instantaneously at about 1500 watts. I like having a strong wheel in back in heavy chromoly dropouts with a thick chromoly torque plate all securely mounted using Nordlock washers.
If my 1.8# tire wears out as quickly as Nep and others caution, I'll then make the greater (4# - 1.8#) = 2.2# tradeoff (double my current rim weight tradeoff) of moving to a DOT tire.
My tradeoff decision is reinforced when I read concerns about 20" drive wheel rim / spoke maintenance issues in threads like this current thread on pizza delivery bikes:
http://endless-sphere.com/forums/viewtopic.php?f=2&t=45841
Chalo
100 TW
Lemlux said:
There are more tradeoffs than just weight, though. Ride quality suffers when tires are mounted on rims with an inside width more than about half the tire's inflated width (because the tire gets a shorter, more flattened cross-section). 12ga spokes are much less likely to stay tight than thinner spokes, so they actually need more maintenance, not less. It's much more of a nuisance to mount and dismount moped tires on moped rims than bicycle tires on bicycle rims.
Spokes that break chronically are not a sign of insufficiently strong spokes, but of poor wheel build quality, flawed wheel design, or poor spoke quality. They don't generally break from overload-- only from fatigue, or stress concentration from a bad insertion angle. It's harder than it looks to get this stuff right on a 20" wheel with a huge diameter hub (which is another point in favor of full-sized wheels), but just using fat spokes doesn't fix the problems.
While it's a good thing for the most expensive/most important part of your bike to be the strongest, it's funny to me that you'd so overemphasize perceived wheel strength while tolerating obvious compromises in the strength of your rear triangle and steer tube, as if those things were much less important.
The intact rear triangle of 1996 Giant chromoly frame is connected through its bottom bracket to the rear dropouts of the complete Gary Fisher frame. In fact, the Giant seat tube portion of the rear triangle is reinforced with a substantial heavy 1/4' by 1" steel bar with pre-drilled mounting holes. This bar, repurposed from a garage door opener's extra parts, is welded to the front of the Giant seat tube.
The spring strut assembly is a matter of concern. It is the weakest structural element and merits constant observation. The strut assembly is made from various aluminum rods and tubes bolted to both the welded-on steel bar and to the cut-off stub of the Giant down tube. If necessary I'll have a welder weld steel members to replace the bolted aluminum. I expect that any weakness in the strut assembly would manifest a lateral movement that would cause the spring to twist and bump an inside edge of the Gary Fisher seat struts for which there presently exists <1" of clearance on each side. Thus far my fabricated spindle assembly with 10mm threaded ends remains firmly mounts the Giant bottom bracket to the Gary Fisher rear dropouts and appears to have almost eliminated lateral tortional flex.
I agree that I have compromised the strength of the uncut steer tube with several spacers and a stem riser. Unfortunately, my body cries out for a more upright sitting position as my legs are disproportionally longer than my arms. After more than a year of using a 26" wide Electra cruiser bar with a 5+inch rise on my normal 29er with OEM pre-cut stem and single 20mm steerer tube spacer, I decided to risk extending this ebike's weaker uncut steerer tube by 3.25" so I could use a 30" wide mtb bar with a gentle 2" rise. This tradeoff was made knowingly and reluctantly with the comforting knowledge that my 260# 66 year old body will traverse nothing more challenging than beginner level XC terrain.
It may be that DOT tires are more challenging to mount on a 16" motorbike rim than the BMX tire which mounted fairly easily. I may or may not find out depending upon the Gravedigger's wear life.
Finally, I acknowledge that I need to check the 12 Ga spokes and retighten as required.
The spring strut assembly is a matter of concern. It is the weakest structural element and merits constant observation. The strut assembly is made from various aluminum rods and tubes bolted to both the welded-on steel bar and to the cut-off stub of the Giant down tube. If necessary I'll have a welder weld steel members to replace the bolted aluminum. I expect that any weakness in the strut assembly would manifest a lateral movement that would cause the spring to twist and bump an inside edge of the Gary Fisher seat struts for which there presently exists <1" of clearance on each side. Thus far my fabricated spindle assembly with 10mm threaded ends remains firmly mounts the Giant bottom bracket to the Gary Fisher rear dropouts and appears to have almost eliminated lateral tortional flex.
I agree that I have compromised the strength of the uncut steer tube with several spacers and a stem riser. Unfortunately, my body cries out for a more upright sitting position as my legs are disproportionally longer than my arms. After more than a year of using a 26" wide Electra cruiser bar with a 5+inch rise on my normal 29er with OEM pre-cut stem and single 20mm steerer tube spacer, I decided to risk extending this ebike's weaker uncut steerer tube by 3.25" so I could use a 30" wide mtb bar with a gentle 2" rise. This tradeoff was made knowingly and reluctantly with the comforting knowledge that my 260# 66 year old body will traverse nothing more challenging than beginner level XC terrain.
It may be that DOT tires are more challenging to mount on a 16" motorbike rim than the BMX tire which mounted fairly easily. I may or may not find out depending upon the Gravedigger's wear life.
Finally, I acknowledge that I need to check the 12 Ga spokes and retighten as required.
Chalo
100 TW
I should have mentioned earlier, but didn't, that I think your rear swingarm suspension is ingenious and looks very effective. A better look shows it to be sturdier than the first photo suggested. I imagine any issues that might arise in the future from the strut portion could be resolved by substituting a welded or brazed part for anything that gives you trouble.
You made a pivot axle? I would have expected just a normal bottom bracket spindle, perhaps with hard washers at the ends to prevent damaging the pivot point dropouts. Did you do that to improve torsional stiffness? In whatever case, a bottom bracket is a more robust suspension pivot than any purpose-built version I have seen on a bicycle.
When I have needed to raise bars much above what a normal stem allows, sometimes I have used a BMX bar to rise 7-8" up from the stem. Because this arrangement offers a lot of latitude to tilt the bars forward or back, the relatively short length of most BMX stems is not as much of a limitation as it seems at first. Just mounting a full height BMX bar vertically adds 2-1/2" to 3" of effective stem length, versus tilting it back parallel to the steering axis.
"CW type" bars, with a continuous piece of tubing along the top, offer the maximum amount of mounting area for controls and accessories. They are inexpensive-- about $15 retail at my shop, with stems available starting at a similar amount.
Your stem riser is probably more than adequate, since I have never observed one to fail on a regular bike. But if you worry about it (which is a healthy inclination as speeds rise above what's normal for bicycles), a BMX handlebar is something that's proven to work for harsh stunt riding as well as more typical stuff.
You made a pivot axle? I would have expected just a normal bottom bracket spindle, perhaps with hard washers at the ends to prevent damaging the pivot point dropouts. Did you do that to improve torsional stiffness? In whatever case, a bottom bracket is a more robust suspension pivot than any purpose-built version I have seen on a bicycle.
When I have needed to raise bars much above what a normal stem allows, sometimes I have used a BMX bar to rise 7-8" up from the stem. Because this arrangement offers a lot of latitude to tilt the bars forward or back, the relatively short length of most BMX stems is not as much of a limitation as it seems at first. Just mounting a full height BMX bar vertically adds 2-1/2" to 3" of effective stem length, versus tilting it back parallel to the steering axis.
"CW type" bars, with a continuous piece of tubing along the top, offer the maximum amount of mounting area for controls and accessories. They are inexpensive-- about $15 retail at my shop, with stems available starting at a similar amount.
Your stem riser is probably more than adequate, since I have never observed one to fail on a regular bike. But if you worry about it (which is a healthy inclination as speeds rise above what's normal for bicycles), a BMX handlebar is something that's proven to work for harsh stunt riding as well as more typical stuff.
Chalo
100 TW
iperov said:
Thinner spokes will require less maintenance in this case, as long as the spokes are of equal good quality. Eyelets are bearings-- they make a wheel easier to tighten and less likely to crack at the holes (but use a drop of oil on each nipple no matter the rim). Deep rims are strong for their weight, but when matching a small diameter 20" rim to a large diameter hub motor, using a flatter rim can make the wheel easier to lace and good spoke angle simpler to achieve. Also, flatter profile rims might or might not have eyelets, but deep rims don't.
Grin Technologies sells Sapim 13ga spokes made in Belgium and cut to order, for a very reasonable cost. Danscomp.com sells Sapim 14ga spokes cut to order for USD 0.25! I have used 14ga Sapim spokes on pedicabs, heavy e-bikes, utility bikes, cargo three-wheelers, choppers, touring bikes, and other high load applications. The only time I suffered spoke breakage was in a internal gear wheel when I made the mistake of using cross-4 lacing, so the spokes inserted at an angle to the nipple.
Whichever spokes you choose, lace them with all the heads inside the flanges, for good bracing angle. If you have a center drill, small countersink, pointed grinding bur, or other such tool, try to smooth and radius the openings of the spoke holes on the outside of the flange where the spoke bend will seat. If there are no sharp edges or corners for the spoke to pull against, it is less likely to break at the elbow.
Don't leave out the stress-relieving step of the process. With such a small wheel, you'll have to do it with the Sheldon Brown pry bar method instead of the Jobst Brandt hand squeezing method.
Chalo
100 TW
iperov said:
Nice truing stand!
You don't really want the very highest tension you can get; you only want enough tension so that spokes are stretched and do not slacken under load. For 14ga spokes and a strong rim, at least 100kgf and not more than 150kgf is a good range. That means, to be stretched the same amount, 13ga spokes would need 135-200kgf and 12ga spokes would need 185-275kgf.
At the higher end, these tensions will damage rims and round off nipple flats. So with fatter spokes, you have to settle for tension that the other parts will tolerate, and either re-tighten spokes often or glue the nipples in place so they don't unscrew.
With such short spokes, it may be difficult or impossible to measure their tension with any commercial tensiometer.
For a critical, high tension build, I use grease with molybdenum disulfide on the spoke threads, and I dab some on the inside of each rim hole (where the spoke nipple head sits) using a cotton swab. If the nipple feels dry or stuck when I am adding tension to the wheel, I'll put a drop of chain lube where the nipple enters the rim.
If you use heavy gauge spokes, substitute linseed oil on the spoke threads, and they'll be gently glued in place within a couple of days.
