Pinions

[cmgreen]

Just wondering if any one knows the difference between 64dp and 48dp, i think it means that the teeth are closer together.
But what does this mean to me, and whats best to use?

[bigred5765]

most cars off road anyway,s use 48dp its the tooth pitch you cant use 64dp if ur cars running 48dp without changing the spur gear as well,

[LEGEND]

On a 64dp pinion the teeth are closer and smaller, and have very little give so if you have a bit to much slack between the pinion and spur it has a high chance of breaking but is a little bit smoother, on the other hand, on a 48dp it has more give, perfect for offroad but not quite as smooth.

[Lee]

LEG END, 64 dp will not affect the "smoothness" of the car all it does is allow for finer tuning of ratios. for instance: Pitch Diameter The diameter of the circle on a gear determined by dividing the number of teeth in the gear by the diametral pitch. In parallel shaft gears the pitch diameters can be determined directly from the centre distance and the numbers of teeth by proportionality. Operating Pitch Diameter (Working Pitch Diameter): the diameter of the circle on a gear which is proportional to the gear ratio and the actual centre distance at which the gear pair will operate. A gear does not have an operating pitch diameter until it is meshed with a mating gear. Generating pitch diameter: the pitch diameter at which the gear is generated. In a bevel or hypoid gear, the pitch diameter is understood to be at the outer ends of the teeth unless otherwise specified. Whereas: From Gear Data Mn = normal module pitch (8) DPn = normal diametral pitch (3.175) ß = helix angle (15) z = no. teeth in gear (61) C' = operating centre distance of mesh () z1 = number of teeth in pinion (17) z2 = number of teeth in gear (61) mg = gear ratio (3.588235294) Formula: Pitch Diameter: D' (known -Mn) = (z* Mn)/cos(ß) = (61*8)/cos(15) = 488/0.965925 = 505.215mm Pitch Diameter: D' (known -DPn) = z/(DPn*cos(ß)) = (61/(3.175*cos(15)) = 61/(3.175*0.965925) = 61/3.066811 = 19.890inches Gear Ratio: mg = z2/z1 = 61/17 = 3.588235294 Operating Pitch Diameter - Pinion: d' = (2*C')/(mg+1) = lee

[notlawnomis]

Or you could just look HERE (http://www.drgears.com/GearTerms/terms/pitchdiameter.htm) :D :p

[LEGEND]

Lee i have a question. Did you look that up or something or can you just remember it off the top of your head? Because i haven't a clue what you just wrote but if it was to say that i was a bit wrong and you looked it up then i am a bit scared. As i have bad feelings about people who try so hard to prove people wrong.:D It is just un-natural unless you realy don't like them.:rolleyes:

[Lee]

Its not proving you wrong matey its basically telling you how DP is worked out, the higher the dp the more efficient the mesh is, ie less energy loss between the gears due to backlash, but there comes a point when it is not really noticable, for instance if you had a ratio of 12:1 with a 48dp and the same with a 64dp you really wouldnt notice any difference in runtime, there really isn`t a large difference in the size of the teeth and they are the same shape ie straight cut gears. A well meshed 48dp gear is as good as a 64dp in my book, i never ran 64dp in tourers either and gearing is possibly more critical with them, especially in 19 turd and stock. There is also the side where the spurs we run are very rarely super true, so a 64dp would be eaten alive as soon as you landed your first big jump of the night.

[LEGEND]

Ok then, Whenever i need to work out the dp then i will give you a call, plus i agree with you for the last part, about it coming off it's first big jump and it being eaten alive.:)

[notlawnomis]

About 15 to 20 years ago we started using 64dp on the offroaders, as the only other option was 32dp!! However once 48dp was released most opted for those, due to the given reason!!

SRM pinions and spurs, blast from the past!!