Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Register Log in
  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Radial markings on oem gear teeth

Status
Not open for further replies.
BrianGar

BrianGar

Automotive
Jul 8, 2009
833
What is the purpose of the radial 'nicks' Im seeing on nearly all automotive helical gear teeth?
The small nicks can lie on centre, to one side, or there can be a few of them - in a radial pattern.

I spent a long time having a quiz with myself as to their function, but Ive just given up.

Random thoughts were to allow trapped oil to escape(somehow)
To break up the loads(doubtful)
Some form of jig marks(odd place to jig)

So, put me out of my misery.

Nicks can be see in image, on the lower gear sets.

Thanks in advance,

Brian,

 
Replies continue below

Recommended for you

Sort by date Sort by votes
You mean the nicks on the gear tooth tips, that correspond to circumferential grooves in the blank?

If so, I dunno. They look intentional. Maybe they carry information, like a date code or lot code, traceable from blank to finished gearset, or maybe they just identify which of several similar blanks you might be looking at.



Mike Halloran
Pembroke Pines, FL, USA
 
Upvote 0 Downvote
Yes Mike, thats what I mean. If they are for ID then they are in a strange place, but the only place they could be I guess.

Ill keep thinking...

Brian,
 
Upvote 0 Downvote
One other thing they could be is witness marks from a steady rest or other workpiece support that's used in roughing the blank.



Mike Halloran
Pembroke Pines, FL, USA
 
Upvote 0 Downvote
You would think they would have machined them away for fear of a possible crack propagation point etc...

Maybe Ill just stop thinking about them and put it down to witness markings.
The last time this happened was when I wondered why trains did not need differentials. 3 weeks later, and nearly insane I figured it out with 'thought power' alone, I should have called it off way before that, or_asked_someone, but I figured it was too obvious to give into. It turned out to be not that obvious at all.

Thanks Mike,

Brian,
 
Upvote 0 Downvote
Trains are tricky; the conical wheels and crowned railheads work to center the trucks. I think that solution was evolved, not synthesized. I found a paper somewhere that explained it all.
A differential in the axle would probably cause truck hunting and greatly increased flange wear.

The tools for rolling splines last a bit longer if the blanks are very roughly turned, so the rack tips don't have to press into the blanks all at once.

<back on, er, track>

Note that whatever cut or rolled the grooves in the gear blanks has a relatively large radius, maybe a mm or four, not strongly likely to start a crack.



Mike Halloran
Pembroke Pines, FL, USA
 
Upvote 0 Downvote
They are identification marks. The grooves do not extend below the tip chamfer so they do not act as stress raisers as no contact occurs there.

More to the point - What is that transmission from? Is that really a scissor gear on the input shaft 4th speed? That must really wreck the efficiency.

M

--
Dr Michael F Platten
 
Upvote 0 Downvote
scissor gear = straight cut?
looks like a fairly typical reverse gear set-up. If so, the gears shown don't mesh with each other. A sliding idler moves into position for reverse
 
Upvote 0 Downvote
No, A scissor gear is an anti-backlash gear. 4th gear on the input has a small part on the left hand side that is slightly offset rotationally from the rest of the gear. This is spring loaded relative to the main part of the gear so that backlash is eliminated from the gear mesh.

These are usually used to eliminate rattle problems, but the added friction is quite significant as the gear is loaded even when idling. It is a pretty last gasp attempt to solve a rattle problem when all else has failed because of the cost and efficiency. You often see them on engine timing or balancer gears because of the high torque fluctuations these gears see.

M

--
Dr Michael F Platten
 
Upvote 0 Downvote
Mikey, thanks for that, and yup, it is indeed an anti backlash 4th. Ill find out where I stole the picture from when I get home. I smiled when I saw it on there, I was just looking for an image for teeth with the nicks.
Odd to see it there, cheaper than a dual mass flywheel perhaps, or an unexpected necessary add on?


Brian,
 
Upvote 0 Downvote
I've seen anti backlash devices like this before, however they are generally not spring loaded.
The ones I've seen are centrifugally disabled as the rotational speed increases.
A series of weights drive the mechanism from within the body of the gear.


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
 
Upvote 0 Downvote
MikeyP is correct, the nicks on the topland are used for identification of gear ratio on many automobile transmissions. I have seen this very recently on an Acura TSX ring gear attached to the differential.
 
Upvote 0 Downvote
Reading your reply again Mike re train diffs, why would one cause hunting? No tyre wall damping effect to take up gear play? Or_what?

Thanks Mike,

Brian,
 
Upvote 0 Downvote
Brian, look for a paper on rail wheel dynamics, probably associated with the TRC in Colorado.


Mike Halloran
Pembroke Pines, FL, USA
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Viet_Doan
  • Locked
  • Question
Forging gear
Replies
12
Views
3K
MC6
MC6
Joel_Lapointe
  • Locked
  • Question
Pressure angle for helical gears, with tangential, axial and radial forces.
Replies
2
Views
1K
pmbrunelle
pmbrunelle
deepnsteep
  • Locked
  • Question
Gear Ratios and BSFC
Replies
9
Views
1K
BrianPetersen
BrianPetersen
Kristoffswe
  • Locked
  • Helpful tip
Need Advice on Replacing NBR 70 Seals in Classic Transmission 1
Replies
2
Views
868
Kristoffswe
Kristoffswe
Charlie144
  • Locked
  • Question
help to finding starter ring gear tooth profile
Replies
3
Views
910
GregLocock
GregLocock

Part and Inventory Search

Sponsor

Back
Top Bottom