Final Drive

[AlastairCooke]

Hi Armortek Owners,
As I about to install the final drive, I am looking for some advice from those who have run their models for some time/distance.

The design concept seems to be that the outer race of the bearings are secured to the casing and the gear is fixed to the inner race of the inner bearing with adhesive. A liberal amount of grease in the casing lubricates the gears and also minimises metal on metal contact should the gear 'end float' into the hull side.

I have noted from the Forum that some are not in favour of wet lubrication and others have taken steps to minimise end float with circlips or affixed a wear pad to the gear face. My question is whether Loctite provides a suitable fixing so that I can dry lubricate and not worry about end float. I could go down the circlip or pad route but that would require more tooling or materials.

Alastair

[AlastairCooke]

Hi All,
Update
Having found and read the advice given in the 'Official Technical Advice from Armortek' section my plan will be as follows...

1. Spray the gear with Rocol Dry Moly with masking applied to part of the face closest to the hull side.

2. Attach a disc of thin (approx 0.3mm) self adhesive Teflon sheet to this face.

3. Glue the gear axle to the inner race of both bearings using high strength Loctite.

Alastair

[Phil Woollard]

Or you could just pack it with a good quality grease and forget about it? Any heat generated by dry teeth or rubbing of the gear face to the hull will cause the packed grease to become fluid and coat those areas.......automatic lubrication system! I have never had any significant wear in this area in maybe 40+ builds.
Bonding the bearings is a great idea.

[Shayne Sutton]

Hi Armortek Owners,
As I about to install the final drive, I am looking for some advice from those who have run their models for some time/distance.

The design concept seems to be that the outer race of the bearings are secured to the casing and the gear is fixed to the inner race of the inner bearing with adhesive. A liberal amount of grease in the casing lubricates the gears and also minimises metal on metal contact should the gear 'end float' into the hull side.

I have noted from the Forum that some are not in favour of wet lubrication and others have taken steps to minimise end float with circlips or affixed a wear pad to the gear face. My question is whether Loctite provides a suitable fixing so that I can dry lubricate and not worry about end float. I could go down the circlip or pad route but that would require more tooling or materials.

Alastair

I am currently building a Churchill, relying on loctite to hold the shaft in place is not a good idea, I will machine a thin spacer between the gear and bearing, then machine a spacer to go between the two bearings, then finally a spacer to go between the tapper lock and the out side bearing, if there is room you could drill and tap the shaft and pull up the shaft before doing up the tapper lock, this way you set the clearance required and the correct gear alignment without the need for lash ups like rubbing pads, ease of disassembly for service is just one advantage without the need to either heat up the parts or apply force to take them apart, You could also use loctite 518 to seal the gear housing to the hull to prevent any ingress from out side of dirt and water, as for lubrication, I will be using a good quality molybdenum disulfide grease on the gears. The 518 remains pliable and allows the removal of the gear case.

[Jerry Carducci]

Hi Armortek Owners,
As I about to install the final drive, I am looking for some advice from those who have run their models for some time/distance.

The design concept seems to be that the outer race of the bearings are secured to the casing and the gear is fixed to the inner race of the inner bearing with adhesive. A liberal amount of grease in the casing lubricates the gears and also minimises metal on metal contact should the gear 'end float' into the hull side.

I have noted from the Forum that some are not in favour of wet lubrication and others have taken steps to minimise end float with circlips or affixed a wear pad to the gear face. My question is whether Loctite provides a suitable fixing so that I can dry lubricate and not worry about end float. I could go down the circlip or pad route but that would require more tooling or materials.

Alastair

I am currently building a Churchill, relying on loctite to hold the shaft in place is not a good idea, I will machine a thin spacer between the gear and bearing, then machine a spacer to go between the two bearings, then finally a spacer to go between the tapper lock and the out side bearing, if there is room you could drill and tap the shaft and pull up the shaft before doing up the tapper lock, this way you set the clearance required and the correct gear alignment without the need for lash ups like rubbing pads, ease of disassembly for service is just one advantage without the need to either heat up the parts or apply force to take them apart, You could also use loctite 518 to seal the gear housing to the hull to prevent any ingress from out side of dirt and water, as for lubrication, I will be using a good quality molybdenum disulfide grease on the gears. The 518 remains pliable and allows the removal of the gear case.

Shayne wouldn't placing spacers as you described, in particular between gear face and bearing (assuming I understood what you wrote) in the final drive housing possibly cause the inner gear face to come perilously close to the lower hull plate? It seems as if it wouldn't allow much clearance surely.

I was as careful as I could be when aligning this area during my M3 Lee construction, I ended up using a grease; 'Sticky Red" on the final drive
without and other mods (save for sealing the flange mating surface on the hull plate) but I try to keep a weather eye on the area. I made no changes to it on the recent rebuild of my Sd.Kfz. 7 however it's an aspect of building I've given a fair amount of thought to. In some of my smaller scale models my final drives are essentially standalone sealed units not unlike their full sized counterparts.

I'd welcome offline discussions of this key area with anyone who has looked at this area of their models. I'm trying to decide which of my larger models I'd like to build next (while eating my Wheaties to prepare) and surely this area is of high interest to me. I'd enjoy comparing notes on this area.

Jerry

[Shayne Sutton]

It would require several trial fits and using feeler gauges to work out the clearance, I had a similar issue on the pivot for the gun mantlet, Armortek say to assemble them with loctite in to the bearings, I machined 1,5mm of the mounting block and made two spacer, this allowed the pivot bolts to be done up tight without the need for adhesive, My tank will be different to yours, I have been involved in maintenance of high speed rotation equipment all of my life and am a qualified machinist and all the bearings I have worked on are located mechanically, not glued into place, a bit of time spent in this area will increase the reliability. Have a look at your vehicle and work out how to lock the shaft into place without resorting to loctite. maybe post a photo so I have a better idea.