View Full Version : home made aluminum rear sprocket

08-15-2012, 08:36 PM
I really hate to write stories, so if I wont include something you guys can just ask me later. anyway.. you can buy a sprocket any size and any kind pretty much, but if you have time, and it is your hobby to do things your self, why waste money if you can also have fun and know that you did it. you can make a sprocket from scratch, all you need for that is a chunk of proper size aluminum or steel and of course the better the material the longer it will last and some tools. but since I already had sprocket made, only for a chain with a different pitch, I decided that I am just going to change the number of teeth and pith I needed. making a sprocket is very difficult because it is gotta be properly measured and then cut, and doing it without a machine but with tools that you would find at home, like hammer, point chisel, hand drill, a few drill bits and grinders, saw, and human eye )) as I said is difficult. so you got to really take your time to measure and mark everything right. I am not gonna tell you how to make a sprocket from scratch, that you can ask me later if you interested, I will try to help you, but I will explain what I did here.
so anyway to begin drilling holes I needed to find - where they are going to be placed and how many teeth? I decided that it is going to be 39 teeth, so, from here I needed to find out on which diameter or radius or circle they are going to be placed, so, to find that , I need to know the size of the chain pitch I will be using, the chain pitch was 12.70 mm. and then I needed to do some math, so take a 12.70 mm and time it by # of teeth, > 12.7 mm X 39 teeth = 495.3 mm of a circle. now to find a radius or diameter of a circle I needed to use formula which most of us learned in school, Pi = 3.141592654. so take 495.3 mm and divide it by 3.141592654 > 495.3 / 3.141592654 = 157.66 mm. that is the diameter. to find the radius that some of you might want to use to measure where the line of the circle will be from the center. you just take the diameter and divide it by 2, and that is how to get the radius. then had to mark a circle, a line where I needed to place holes for the chain. and then on that line I put marks of the pitch, every 12.7 mm. and 39 of them. but because chain is not completely round when seating on the circle, but sort of angled, the circle will be bigger. 0.5 mm about the circle line did it for me. if first mark of the pitch does not match with the last mark - you made a mistake in your measurements, find your mistake and do it again, don't do any chiseling or drilling before that. once you mark the pitch and it is all good, take a sharp chisel and hammer a hole so when you will be drilling with the drill bit, the bit wont run away and drill a hole where u don't want. when you start drilling use a very small drill bit, then move to bigger gradually and stop at the size that is right for your chain. remember you gotta drill it at 90 degree angle. after you did that take a saw, and sow off not needed junk) like you see on the picture. after placing a "sprocket" on the wheel I find it easier to grind and finish the teeth of the sprocket. so there you go.

08-16-2012, 04:26 AM
nice work bud! thanks for sharing

i was interested for making one in the future but then the maths hit me lol

08-16-2012, 06:11 PM
Nice work mate, im just wondering how long it lasts compaired to steel.

08-16-2012, 11:16 PM
honestly, I don't know, you should ask some one who has more experience. I never wore one up.

08-18-2012, 10:16 AM
all I could say, that it will out last your top end, my for sure ))) some heavy bikes with a lot of hp have aluminum sprockets, and they last them. 50 - 80 cc?.. my tire wear faster than a sprocket )))

08-18-2012, 07:39 PM
Okay, that is stupid....

If you do not have a mill you can forget to make that. Aluminium is solft and the chain will rape it in 10 minutes.

08-19-2012, 01:58 AM
I got one of the Aluminum sprockets from the AF1 shop <link> (http://www.af1racing.com/store/Scripts/prodView.asp?idproduct=1165) and it's held up to a few race weekends and about 30 hours of summer riding around town without any unusual wear. Maybe wears faster than steel and for the minuscule weight savings I will probably just go for a steel one next time. It's not like a few grams will make a difference on lap times for the 50cc class. :lol:

08-19-2012, 10:12 PM
one thing is stupid norway guy, but it's aint that on what you are implying. if you know what I mean :-D you see, that sprocket was with my 250cc engine, I put on that a good amount of km and power wheelies. as much as I see there is no wear to my eye, but yeah, as US guy said, it wears faster than steel, but the material does matter. that sprocket was made in the US, meant for go card racing, and shit it's about 3 time lighter, and that particular one right now is about 4 times lighter than the stock one I had. it depends on what anybody is looking for. I personally like the formula 1 race car. why do I say that ? a few grams or a kilo, big difference or small, I go for the performance, every 100 penny makes 1 dollar. and I like cool shit. if anyone wants a steel sprocket let him have it. I want my sprocket to be aluminum and chrome plated, or cermet coated for wear. anyway norway guy, do your f**king research )) one more thing I gotta say, if both of your hands are growing out of your ass )) than even a mill wont help you )

for the US guy - every gram matter for the 50cc class more than any higher class, because 50cc engine makes such little amount of torque and power. if you loose 1hp on 10hp bike, that is 10% of total power. if you loose 1hp on 100hp bike, that is 1% of total power. big f**king difference isn't ?? and that is not the biggest issue that 50cc has, 50cc lacks on torque big time, so weight and aerodynamics have a big affect on this bike if you wanna go fast, in this class every bent and twist matters. you will pull a hand out of the fairing and you will "steer" the bike the other way )))) if you guys use Internet properly, you would be teaching me right now, and not the other way around )))))

08-20-2012, 12:25 AM
Aluminium Sprockets on bikes are not "Aluminium" but an Aloy mix of difrent metals.

btw, my sprockets never outlasted my topend ever... think i wear out 2 tires for each sprocket, if im lucky... but these sprockets are so narrow for the power these engines can put out, so they got aftermarket asprockets and chain for these bikes that are a lot wider than stock.

08-20-2012, 01:30 AM
"Aluminum" Sprockets on bikes are not Aluminum but an Aloy mix..

what are we debating here? for does who don't want a sprocket made of such material - don't have it.
I will use this sprocket and I will let you know when I will wear it out, so you will know how long it lusted me. maybe in a few years you'll see me say - it's worn, don't wait to soon because with my seasonal riding, it is not going to happen any time soon. besides this bike is a toy to me, that's all it is. if your bikes are your every day transportation, and you rely on it, then u should use a tank bulletproof material. are we all clear ? and thanks for all your comments ) peace
ow.. and one more thing, real racers, will choose all performance things for their machines to Finnish the race first, because of the way they think - "if it is not helping 'em go faster- it is slowing 'em down." and I like that.

08-20-2012, 01:47 PM
got some news for you guys about my sprocket. and it is a slap in my face. ))) but hey, I am gonna stand here and take it like a man. my sprocket fail. )))) apparently two holes that I drilled had improper measurement which in result cause the pitch to shift, twice in different areas, shifted once and then shifted again in the opposite direction and it does that every revolution. just noticed today. it is not that visible and it doesn't really to the feel. but it is a bit off. for temporarily use, I guess it is fine for now. good experience))). but yeah, it's a shit, no good. it is anything but performance. gonna order one that is already made ))))))) cheers guys)

08-20-2012, 04:50 PM
-CON-, I'm getting embarrassed of the Norwegian guy here..
Please don't call him "the norwegian guy" haha :)

I like that you actually made it yourself, it would probably wear out quite fast but it's a nice sprocket to be "home made" :cheers:

08-20-2012, 09:37 PM
I like that you actually made it yourself, it would probably wear out quite fast but it's a nice sprocket to be "home made" :cheers:

:plus: Indeed. I don't think I'd ever try this myself but thanks for the good write up and pictures. I never would've thought this type of part could be made without some type of CNC machine or at least some heavy shop equipment.

08-21-2012, 12:53 AM
sorry ) you are right, I shouldn't be calling him that. it was just easier. I don't mean to be disrespectful to anyone.

08-25-2012, 03:52 PM
I ment with the Aloy that those light weight "aluminium" sprockets are not made of pure aluminium but a mix of difrent metals to make it harder and more wear resistand, didnt mean anything else with it... just pointed out that over the shelf aluminium sprockets are an aloy mix like Ergal and not just "aluminium"

Think most of us understand you do not use your bike as a daily driver and its just a fun bike for you, so its not a problem if it wears out faster for you.

10-13-2012, 11:58 PM
nice sprocket