hope someone can help....I have a '58 Pan running the 2 brush generator. I have a timing gear whine.
I have a 13 tooth gear fitted, as per all the catalogue listings, but Bruce Palmer (H.T.R.Y.H.D) clearly states that the gears for OHV should have 14 teeth....as far as I'm aware all the gears/cases etc are standard, but the genny is not the original.
Any suggestions ?......should I try a 14 tooth, or will cause damage ?
generator drive gear
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Cotten
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Guest!
Lest you chase your tail,
Pull the generator out far enough to dis-engage the gear, and start the motor to listen again for the whine.
It might be everything else. Maybe.
If the whine disappears, then let us consider shimming as well as a different gear.
Adding a tooth allows your system to reach its optimum at a higher RPM, which has its advantage on modern highways.
...Cotten
Lest you chase your tail,
Pull the generator out far enough to dis-engage the gear, and start the motor to listen again for the whine.
It might be everything else. Maybe.
If the whine disappears, then let us consider shimming as well as a different gear.
Adding a tooth allows your system to reach its optimum at a higher RPM, which has its advantage on modern highways.
...Cotten
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FlatHeadSix
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Cotten and guest
Excellent advice as long as you qualify it, faster is not always better. If you actually have a 2 brush generator and a regulater (not a 3 brush with a relay), then increasing the speed will increase the output. Placing the correct amount of shims under the generator will reduce the noise and backing the generator away from the gear train will tell you if the noise is actually coming from an incorrect lash or gear tolerance between the generator gear and the drive (idler) gear.
Just wanted to add a word of caution here, faster is NOT better on a 3 brush system: the faster they run the less they produce!
mike
Excellent advice as long as you qualify it, faster is not always better. If you actually have a 2 brush generator and a regulater (not a 3 brush with a relay), then increasing the speed will increase the output. Placing the correct amount of shims under the generator will reduce the noise and backing the generator away from the gear train will tell you if the noise is actually coming from an incorrect lash or gear tolerance between the generator gear and the drive (idler) gear.
Just wanted to add a word of caution here, faster is NOT better on a 3 brush system: the faster they run the less they produce!
mike
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Cotten
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Mike!
The 14T gear spins the generator slower than the 13T gear, thus it reaches it's optimum at a higher engine rpm.
That's why adding a tooth helps for the highway.
And Guest!
Don't forget that how far the gear protrudes into the case can be shimmed, albeit marginal as well.
By the Parts Books the 14T gear (31073-63a) was supposed to be for 45"s, and the 13T gear (31070-58) was for 74"s, but they are often found swapped with little concern. Probably because sportsters used the 14T, maybe. (I pay little attention to them.)
Note that the three-brush generator gear (31070-30) used on Big Twins through '57 had 14 teeth. And the idler gear that drives the generator gear never changed.
...Cotten
The 14T gear spins the generator slower than the 13T gear, thus it reaches it's optimum at a higher engine rpm.
That's why adding a tooth helps for the highway.
And Guest!
Don't forget that how far the gear protrudes into the case can be shimmed, albeit marginal as well.
By the Parts Books the 14T gear (31073-63a) was supposed to be for 45"s, and the 13T gear (31070-58) was for 74"s, but they are often found swapped with little concern. Probably because sportsters used the 14T, maybe. (I pay little attention to them.)
Note that the three-brush generator gear (31070-30) used on Big Twins through '57 had 14 teeth. And the idler gear that drives the generator gear never changed.
...Cotten
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King
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My thanks also Cotten. It appears that there is no problem using either as you said. The Cycle Electrics website has this to say on the matter.
"13 tooth vs. 14 tooth
1936-1957 models used a 14-tooth generator gear. 1958 and up big twins used 13 tooth gears. Sportsters use 14 tooth gears. From 1936 to1957 the gear was held on with a pin. On 1958-up models the gear was held on with a nut. The old gear will fit on the new generator but the nut must be used.
On 1957 and earlier models since gear mesh is adjustable it may be possible (depending on manufacturing tolerance) To use a 13 tooth gear if proper gear mesh can be achieved. This will increase low speed generator output from 2 amps to 6 amps. This is important when using small batteries."
As both of you noted the issue will be gear mesh (lash). Cycle Electrics says this:
"Shimming and strapping from 1936 to 1957[/b][/b].
The mesh between generator gear and idler gear was adjustable. To achieve proper gear mesh use paper shims between the generator and cradle on the motor. When proper gear mesh has been achieved (.002 lash at tightest point) snug strap, tighten mounting bolts then tighten strap. On 1958 and up models the gear mesh is set by manufacturing tolerance and is not adjustable. These models have no cradle or strap".
I assume you install generator into the cradle and with the gear case cover off, add or subtract shims until you achieve the proper lash, then zip up the case and tighten the strap. Sounds simple enough we’ll see how it goes in practice.
The Cycle Electrics site is a wealth of information on installing and testing gennys and alternators. I highly recommend a visit.
King
"13 tooth vs. 14 tooth
1936-1957 models used a 14-tooth generator gear. 1958 and up big twins used 13 tooth gears. Sportsters use 14 tooth gears. From 1936 to1957 the gear was held on with a pin. On 1958-up models the gear was held on with a nut. The old gear will fit on the new generator but the nut must be used.
On 1957 and earlier models since gear mesh is adjustable it may be possible (depending on manufacturing tolerance) To use a 13 tooth gear if proper gear mesh can be achieved. This will increase low speed generator output from 2 amps to 6 amps. This is important when using small batteries."
As both of you noted the issue will be gear mesh (lash). Cycle Electrics says this:
"Shimming and strapping from 1936 to 1957[/b][/b].
The mesh between generator gear and idler gear was adjustable. To achieve proper gear mesh use paper shims between the generator and cradle on the motor. When proper gear mesh has been achieved (.002 lash at tightest point) snug strap, tighten mounting bolts then tighten strap. On 1958 and up models the gear mesh is set by manufacturing tolerance and is not adjustable. These models have no cradle or strap".
I assume you install generator into the cradle and with the gear case cover off, add or subtract shims until you achieve the proper lash, then zip up the case and tighten the strap. Sounds simple enough we’ll see how it goes in practice.
The Cycle Electrics site is a wealth of information on installing and testing gennys and alternators. I highly recommend a visit.
King