long addendum gear

[fluevogg]

I'm trying to get an involute profile for a non-standard pinion that turns a rotary kiln for a pulp company. The given information I have is:

Outside D = 20in
Diametral Pitch = 1
# of teeth = 17
Pitch Diameter = 17"
150% High addendum
Pressure Angle = 20°
Center Distance = 116.5in

The long addendum seems to confound any gear generating program I have. If anyone could assist me with this profile it would be greatly appreciated.

 

[mfgenggear]

Fluevogg

are you able to obtain a measurement over (2) 1.92 wires or wires that are close to this size.

Base Dia = 15.9748
TIF at approx 5.57 deg = 16.050 dia.
for coarse pith should be approx 5 deg TIF, to be more exact I would need the exact CTT & Major diameters of both mating gears, with my program anyway.

 

[israelkk]

How are you planing to cut the gear?

From the center distance it appears that the mating gear has 215 teeth.

If the pinion is manufactured on the gear cutting machine you do not need the tooth profile but dimension over 1.92 inch diameter pin or any other gear measuring method data such as testing radius when mated with a master gear (probably too fancy for such a gear).

If you want to cut it by other mean such as on a CNC machine or wire EDM you need an exact dxf file of the gear profile.

http://israelkk.googlepages.com/home

 

[fluevogg]

Thank you for the quick replies;

I have little experience developing gear profiles, especially non-standard ones. The mating bull gear has 216 teeth and the pinions outside diameter is 20in. I don't have the diameter for the bull gear but I have approximated a working depth of 2 1/8in.
What I have are pictures of the worn profiles (which are still in service) and I require the theoretical profile so we can do some analysis.

 

[mfgenggear]

Fluevogg

Just FYI the involute of the pinion gear can not go below
the base diameter, which is the start of your involute profile, which is o deg.

For a coarse pitch gears like i said earlier the TIF(Total Involute Form is usaully at 5 degs.

Israelkk comment about your approach in machining this
gear is concern.

you need to make sure both gears "the pinion & the bull gear" have the same involute form. it would be wise
to have an involute profile verification by a consulting company that has CNC Gear inspection capability.

That said if it is a standard involute then it may be machined by a standard gear hobbing/machining method.


You should to do these test

#1 verify measurement over three wires (most accurate method), or span measurement over "x" nuber of teeth.
#2 record Major & Minor dia

#3 verify the Involute profile.
(this will verify if the DP & PA are correct.

just a note the standard hobbing or shapping will produce a std Involute Profile.

if you wire cut the involute profile like Israelkk said
it will require an exact gear profile DXF file.

 

[dimjim]

The 150 percent is simply a 50 percent long addendum
so the outside diameter is 17.00 plus 2x1.50 equals
20 inch diameter. If the pinion is hobbed the manufacturer
simply withhold his cutter .50 creating the 50 percent
long addendum. The circular tooth thickness is increased by 2 x tan 20degrees and the circular space is decreased by
the same amount. I would assume that the backlash specifications for the pinion would be .000/.005.
I assume you are using a 215 tooth gear meshing with this pinion. So basically the center distance is 215/2 plus
17/2 plus .50 yield the 116.50.

 

[dimjim]

I forgot to mention that you have to subtract .50 from
the dedendum.

 

[mfgenggear]

I made a mistake on my last post
it should be verified by measurment over (2) wires
and not (3) wires.

let me say this, if the existing MOW is held
then you are assured of holding the backlash, &
the required circular tooth thickness of the gear.
stress factors and so on.

depending the the gear if it is standrd or not standard.
and if the tool used is standard.
there are varibles to consider.

Is wise to verify & document the gear.
also hold to the same mow & minor dia, then you are assured
it will mesh correctly with the existing mating part.
just my 2 cents

 

[fluevogg]

Thank you all for the information.
The gear actually has 216 teeth. I have aCAD & Inventor so I can model the gears and then do an analysis. I suspected the tooth thickness was increased.

 

[israelkk]

What kind of analysis you can do with ACAD & Inventor These are just 3D modeling programs?

How are you account for backlash, tooth width tolerances, roundness, Center distance tolerance, etc.?

If the tooth height is 2 1/8" then this is not a full depth tooth gear which should has 2 1/4" tooth depth. You should find to what spec they were designed and manufactured.

If the bull gear has 216 teeth then it has -50% reduced addendum.

 

[fluevogg]

What I'm hoping to achieve is to simulate the movement of the teeth in mesh to try and determine why they are vibrating, possibly due to gear wear & root depth. It is suspected that the pinion flank is being hit upon engagement.

 

[israelkk]

This is not the way to do it. If the gears are designed and manufactured correctly as I mentioned in my previous posts then it should work fine. Doing a 3D modeling will not help to my best knowledge.

The pinion and the gear must be manufactured by hobbing or fellow this will create the correct tooth geometry. Wire EDM or even CNC milling is possible given that the exact DXF representation of the gears is produced including the trochoid at the tooth root. However, someone needs to correctly define the gear dimensions and accuracy system.

I suggest you look for a respected gear consultant and gear manufacturer who is equipped for such large gears.

 

[fluevogg]

Yes well I knew I was over my head when I saw the long addendum and all the gear generating software at my disposal blew up. There is no existing drawing that shows the theoretical new tooth profile. I thank you all for your input and I have already contacted a gear manufacturer about a DXF profile.