Output gasket for Omni gearbox on landpride rcr1248

[marrmanu]

The seal on my rcr1248 was leaking so I pulled the output cap to replace the seal. So now I need to replace the output cap gasket. The parts diagram https://messicks.com/catalogs/landpride/rcr1248/section-3-blade-drive/gearbox-826-670c-omni
shows three different gaskets for that cap.
I measured the old one at .1 mm, if my mic is accurate. The old gasket is of the paper variety. I ordered a gasket off the parts diagram (messicks) .1 mm and received a plastic gasket that my mic does not register any thickness?
Does anybody know why there are three different gaskets listed?

thx for looking Mike

 

[Russell King]

From looking at the diagram the gears are meshing together at 90 degrees so I would think they need the meshing set so they have the correct contact pattern.

I think you will need a work shop manual to show the proper pattern. The cover seems to position the gear so the gasket acts as a shim to move it out.

 

[Flintknapper]

Agree with @Russell King. Likely the thickness of the gasket has to do with setting the correct 'contact pattern' for the gears. Not unlike a tradtional differential where Pinion Depth into the Ring Gear is important.

If you ordered and received a .10mm replacement gasket, your measuring device should be capable of showing it.

.10mm is roughly 4 thousandths of an inch. Just about any quality Micrometer or Caliper set would easily record that.

 

[Fedup]

As I see it the gasket has no bearing on gear contact adjustment. The bottom bearings and spacer sleeve fit into a machined bore in the case. Actually (unless I missed it) I don't see any shims anywhere for contact pattern adjustment. The gasket in question is variable only to fill the gap between the case and the bottom cover. I would fit the cover without a gasket, snug the bolts slightly and see if there's much gap between the case and the cover. Then go from there.

 

[marrmanu]

My neighbor with machinist background came over and he determined my mic was not measuring correctly.
As a result it looks like I need the .15 mm gasket, $59 ouch! Probably why my mic was not measuring that extra half mm .

Thx all for the replies.

 

[marrmanu]

As I see it the gasket has no bearing on gear contact adjustment.

I am baffled by the three different gaskets as they are the only parts other than the input cap gaskets that have multiple pats numbers. No other parts have multiple numbers. And how would you determine contact pattern in a seal case or backlash? Maybe its a little different not being a ring and pinion setup.
I am going to use some plactigauge to hopefully confirm that gap.

Thx for reply.

 

[Fedup]

Checking contact pattern would be just a "peace of mind" thing, as no shims or adjustments appear to be involved. Straight cut gears really don't require that anyway. If all you're doing is replacing bottom seal and gasket it won't affect gear contact anyway. If the backlash "feels" reasonable, run it.

 

[ruger1980]

As @Fedup said the bearings and spacer are going to create a solid assembly and there is no adjustment for gear position. I suspect the correct assembly process is to assemble without a gasket and the bolts finger tight. Then measure the gap with feeler gauges and adjust the gasket thickness accordingly so that you have some crush to the gasket when tightened.

 

[PoTreeBoy]

My shadetree 'friend' says put it together dry and see if it turns freely with a little backlash. If so, put a thin bead of oil resistant silicone seal on and bolt it just past finger tight. Let it sit overnight, tighten it up and run it. Use ~80w gear oil, your flavor.

 

[marrmanu]

My shadetree 'friend' says put it together dry and see if it turns freely with a little backlash. If so, put a thin bead of oil resistant silicone seal on and bolt it just past finger tight. Let it sit overnight, tighten it up and run it. Use ~80w gear oil, your flavor.

Being a apprentice shadetree mechanic I am going to go down this road. My initial thought was to make my own gasket, however finding .15 mm gasket material proved hard to do.
My thanks to all the great responses.

Mike M

 

[Fedup]

If there's any gap at all when you dry fit the cover, I wouldn't use the silicon method. You don't want to rely on silicon to fill a gap. Too much chance of cracking the flange. I've made plenty of shim gaskets from nothing but computer paper. Often I just use the receipts they print off when I purchase the bearings, seals, ETC.

 

[GreensvilleJay]

hmm .15mm seems to be real close to 6 thou. ?? I have a can full of 6" wide, 6 though brass 'shimstock'.