Making a transaxle with straight cut gears, quiet?
Making a transaxle with straight cut gears, quiet?
(OP)
Any thoughts on how to quiet a straight cut gearbox? simple is better (as opposed to Comanche helicopter style electronic noise cancelation, etc.)
-Dave
Everything should be designed as simple as possible, but not simpler.





RE: Making a transaxle with straight cut gears, quiet?
Rod
RE: Making a transaxle with straight cut gears, quiet?
-Dave
Everything should be designed as simple as possible, but not simpler.
RE: Making a transaxle with straight cut gears, quiet?
More serously, you are facing an uphill struggle. That's why virtually every production gearbox uses some form of constant contact (ususally helical) gears.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Making a transaxle with straight cut gears, quiet?
Cost vs. noise vs. power handling...its a viscious circle :)
Thanks for the input
-Dave
Everything should be designed as simple as possible, but not simpler.
RE: Making a transaxle with straight cut gears, quiet?
The most effective thing you could do is cover the transmission with a damping layer such as the three layer aluminum and urathane stuff you can get. the problem with this is the possiblilty of trapping to much heat and damaging the transmission.
RE: Making a transaxle with straight cut gears, quiet?
SIMPLE is...buy yourself a case of those little yellow foam ear plugs and put ATF in the gearbox!!!!!
Rod
RE: Making a transaxle with straight cut gears, quiet?
Actually, I think we're either going to leave that gearbox option noisey on the street, or find a different box.
Thanks for the input!
-Dave
Everything should be designed as simple as possible, but not simpler.
RE: Making a transaxle with straight cut gears, quiet?
Norm
RE: Making a transaxle with straight cut gears, quiet?
Make that "virtually every production *CAR* gearbox" uses helical gears, and I'll agree.
For those of us who deal with straight-cut gears on a daily basis, however, Gunman's question is a good one; unfortunately, there are few simple answers.
I deal with transmissions for which I can identify in the interior noise spectrum the .5, 1st, 2nd, and 3rd harmonics of both input gearset and output gearset tooth passing frequencies, and sometimes they are VERY annoying!
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Gunman:
One thing to be done is to have straight-cut gears that are as near perfect as possible, then hone or polish them to improve the surface finish.
Having as rigid a case as possible helps to reduce the radiation efficiency of the gearbox. Think ribbing.
Next, the gearbox shafts must be as stiff as possible and the gear assemblies rigid to avoid harmonics of the gear-tooth passing frequencies from generating noise.
The mounting of the gearbox to the chassis should be as compliant as possible to eliminate sound transmission paths, and clutch rods or clutch cables should also have rubber mountings to the transmission/clutch housing and to the body, again to avoid being a transmission path.
The shift lever should incorporate rubber isolator(s) for the same reason.
Then if the gearbox has an oil cooler, it can have sound barrier/absorber panels affixed to its surfaces; but not if there's no cooler! Mechanical gearboxes generate more heat than you'd think.
Finally, the driveshaft should incorporate damping material to avoid excessive ringing especially at the geartooth passing frequencies.
Remember: It's not how much noise the gearbox makes that's important, it's how much gets to your ears!
Regards,
- R
RE: Making a transaxle with straight cut gears, quiet?
-Dave
Everything should be designed as simple as possible, but not simpler.
RE: Making a transaxle with straight cut gears, quiet?
RE: Making a transaxle with straight cut gears, quiet?
Ive heard banana skins work in diffs.
Ken
RE: Making a transaxle with straight cut gears, quiet?
When my dad retired from the fire department in 1958, he bought into several businesses...pawn shops, used car lots...where I worked part time (and a couple gas stations). One of the primary sources of income for me was to take the 'clunkers' that could not be sold on a lot and sell them through the classifieds...Let me say up front, that was a looooooong time ago and the mechanics(?) at the lot really did some baaaaaaaad things to cars that were sold. Saw dust, bannana peels, egg whites in the radiator for stop leak... Lots of other things to get them to run long enough to make it across the border. The cars usually would not pass the Texas safety inspection and most were sold to be exported (illegally by the purchaser, I might add) to Juarez, Mexico.
All this is not legal or moral, then or now. I do sincerely hope that these things are not still as common a practice as they were in the 50's...I have my doubts.
Rod, "Would you buy a used car from this guy?"
RE: Making a transaxle with straight cut gears, quiet?
RE: Making a transaxle with straight cut gears, quiet?
RE: Making a transaxle with straight cut gears, quiet?
Ken
RE: Making a transaxle with straight cut gears, quiet?
I'm not a gear design engineer, but it seems to me that straight-cut gears are a bit stronger, and if space is an issue, as when squeezing 6-speeds into a gearcase designed for a five-speed (or 4-speed!), you might wish to have the greatest amount of strneght possible, in a gear that's smaller than was originally used.
RE: Making a transaxle with straight cut gears, quiet?
Rod
RE: Making a transaxle with straight cut gears, quiet?
RE: Making a transaxle with straight cut gears, quiet?
Virtually every heavy truck (Classes 6 through 8 in North America) has a gearbox using straight-cut gears throughout, and which are usually dealing with 1650 - 2050 lb-ft of torque.
While noisy, it's not the gearbox you hear when one drives by.