[R-390] R-390\URR Geartrain Problem

[Jacques Fortin]

Hello Mark.

I suspect that the rack slides are dirty and that the rack rollers are stuck
(thus not "rolling" anymore).
My advice is that you have to remove all the racks (number those before..
more easy when you re-assemble).
Clean everything ! Clean also the gear train the best you can.
BTW, you really have to replace the stripped gear clamps screws !
Re-align the cam positions at 07+000 very carefully.
Lubricate all the gears with synthetic oil (some uses Mobil synthetic oil,
but I used Finish Line "Cross Country" Synthetic Bicycle Lubricant).
Lubricate the rack rollers with the same (free them if they are stuck).
Re-install the racks one by one and check their operation thru a complete
travel (from both MC and KC tuning knobs).
Lubricate the slides lightly with synthetic oil too..
At the end, everything should operate easily and smoothly.

73, Jacques, VE2JFE

-----Message d'origine-----
De : R-390 [mailto:r-390-bounces at mailman.qth.net] De la part de
hackmohr at myfairpoint.net
Envoyé : 21 mars 2017 12:39
À : r-390 at mailman.qth.net
Objet : [R-390] R-390\URR Geartrain Problem

Hello All,

It's been a year and a half since I last posted here. It took that long but
I finally found the spare parts I need to continue a R390\URR rebuild. I've
got the RF Deck out again and a mostly complete spare deck for parts. I have
some questions about the mechanical side of things. I'm not a gearhead so
I'll try and keep my nomenclature as accurate as I can.

There are 2 inner cams on the 2nd variable IF camshaft which control the
motion of the 1st IF can rack. These cams have a rounded convex side, a
sharply pointed peak, and a rounded concave side. The IF can rack rollers on
both of my decks have no problem traveling up the convex side to the peak
and down the other side. But reversing the geartrain movement, the rollers
get stuck on the concave side of the cams and are unable to travel over the
peak. The cam edge is almost vertical and presses against the rollers rather
than allowing them to travel up and over. The geartrain drags down as the
camshaft spins inside the gear. On both decks the gear clamp screw is
stripped and unable to tighten around the camshaft. (As if countless techs
have tried to fix the problem by just tightening the gear clamp enough to
force the rollers over the cams)

I haven't yet pullled the IF can rack apart but I'm assuming that the
rollers stuck against the cams is something that can be adjusted out? Any
help will be appreciated. Thanks.

Mark
WA2FXM
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