mechanism for gear alignment

[sbrats]

Hopefully someone can help me here. I need to have 2 gears in a disengaged position. During operation normal use - one rotates and the other is stationary. When required I would like to engage the teeth of the gears engaging a damper to control the rotation of the first gear. Since the first gear can stop in any rotational position and because of this there is a chance that at this position the teeth will not line up for engagement. Anyone have a suggestion to guide the second gear to the first engaging the teeth. (can't use friction, as in, have the gears engaged and use a clutch to engage the damper)
If I have posted in the wrong forum let me know please.

Thanks

Stephen

 

[dgallup]

Generally speaking, most transmissions keep the gears engaged at all times and slide dogs on the shaft to lock the gear or let it free wheel. The dogs typically have four engaging ears with large free space so they slide into engagement easily.

 

[patprimmer]

Have the sliding gear mounted on an intermediate hub.

The intermediate hub should mount on a low angle helical spline, and the gear should mount to the intermediate hub on a straight spline.

The gear should float, but be spring loaded to the engaged position. The selector should act on the intermediate hub.

Just my initial impulse answer. I have not thought it through in detail. Have I shot from the hip and missed something.

Regards

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[thundair]

I am a fan of planetary gear sets, and I have a situation where my ring gear is locked in position, and the planets are engaged through a clutch.

Just one option to look at..


Cheers

I don't know anything but the people that do.

 

[GregLocock]

I suppose a very sloppy fit of the stationary gear on its shaft is out of the question?

It'd probably help if you gave us a hint about sizes, speeds, power etc, and whether cost is an important consideration.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[BobM3]

Can you incorporate electronics? Use resolvers or encoders to give a microcontroller the angular positions of the two gears and then have the microcontroller output a signal to a solenoid that engages the gear at the right time.

 

[patprimmer]

If both gears are stationary and the points of the high spots on the dogs are perfectly lined up, it won/t engage, just like happens with low and reverse when selecting while stationary and it sticks without engaging. Let out the clutch to spin the first motion shaft and try again, only in this case, no mechanism to replicate engaging the clutch and moving the first motion shaft is available.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[scarecrow55]

You must slow the thing right down & take the load off to avoid any damage, put chamfers on the teeth ends to start with. I suppose a gear ring bonded by rubber to a central hub might take out a bit of shock but I reckon without somesort of syncromesh unit you won't avoid shock.

 

[sbrats]

Sorry guy's been really busy. I was pretty vague with the details. I have a space application, but since we are talking gears here. No electronics, no rubber, just mechanics allowed. I know that this will go against the norm. I have 2 spur gears in the same plane, but engage on the tangent. The center shaft rotates at a slow rate but the other gear is connected to a eddy current damper and is not rotating. The simple solution is to have a switchable damper (open and close the shunt) with the gears permanently engaged. However just in case I can't do this I am trying to think of a way to engage the 2 gears.
I have modeled a number of concepts that my Sr Eng's have shot down (but not offered guidance)including..
1) engaged gears with dog face slide engage through the use of a lever. (to complex they said)
2) clutch faces (friction not allowed)
3) slide axially the 2 spur gears together with champers on the edges of the teeth.

Cost - unlimited to a point (this is space)
gear ratio - 1:1
torque - 600 in/lbs
speed - 1 degree/sec
total rotation is only +/- 135 degrees

one way or another I will make this work, I as trying to think of a way of having a follower on the stationary gear that would mechanically follow the rotating gear and keep track of the moving teeth. Since the damper doesn't offer resistance at low speeds (fractions of a degree/sec) i could have the damper follow the indicator slowly rotating as it engages. The environment is very cold with large temp swings. Lube and thermal tolerance's are a huge issue.

I could be up the creek as they say - I prefer number 1 or 3
so this may be my backup, but simplicity is king.

Thanks for listening.

Stephen

 

[patprimmer]

At those speeds 3 sounds good to me.

A dog clutch can also be very simple.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MikeHalloran]

This is probably too complicated for your mentors:

Dog clutch:

- one half with regular dogs.

- second half with a large number of small spring loaded sliding pin dogs; think of one of those one size fits all socket wrenches. On engagement, some of the pin/dogs will be blocked and the springs compressed. Some will not be blocked, and their edges will engage the mating dogs.



Mike Halloran
Pembroke Pines, FL, USA

 

[sbrats]

Thank you for the responses.

Best wishes.

S