Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

[2oldteslas]

If anyone is interested here are the dimensions of my home made from scrap iron press to remove the rotor from the case. Inside dimensions: width = 12.75", length = 28", hole for rotor shaft and bearing = 3.25", height of bottle jack cradle = 2.25", length of cradle =7". This press was designed to be used horizontally on the floor or a bench. The LDU must be turned so the gearbox faces up. Shims can be added to the case end to prevent the windings from contacting the face of the press. The height of the bottle jack centerline is matched to the 5.5" centerline of the rotor splined shaft. Your jack height may vary depending on what jack you use. It takes very little force from the press compared to a hammer to remove the rotor and it is much more controlled. I have not yet tested the press to remove the inner rotor ceramic bearing but I suspect it will be just as useful once the pinion shaft is removed.

[muehlpower]

Disassembly Notes:
I cut an M10 thread into the through hole and screw in a screw. Then I press from the opposite side with an M8 screw. For blind holes I use self-made push-out screws. Also works with the case halves. The last picture shows how I push the rotor out. No hammer needed and won't destroy paint on nicely made engines.

[jrbe]

Disassembly Notes:
I cut an M10 thread into the through hole and screw in a screw. Then I press from the opposite side with an M8 screw. For blind holes I use self-made push-out screws.

Are the self-made push out screws dog pointed bolts or the threaded collar ones you showed?

Could also probably be made like this but likely stepped down more than this image shows..

That's an old Audi I5 timing belt idler "puller".

It's too bad Tesla didn't do this from the factory. Nice solution muehlpower!

[muehlpower]

I use Allen screws DIN 912. With your one-piece design, the depth of the blind hole is important, with the two-piece design, the large screw can be screwed in completely and the small screw can be adjusted or simply be very long.

[howardc64]

Took apart the LDU rotor and seal 3k+ miles after rebuild as its making slightly louder noise along with finding rusty streak on the speed sensor. Coolant seal shaft surface is rusted and grooved. The mystery is where did the rust come from?

IMG_0647.jpeg

IMG_0645.jpeg

IMG_0641.jpeg

IMG_0643.jpeg

Coolant shaft surface

Rusted and pitted. Rust particles got trapped between the triple lip seal lips and grounded away the surface

Seal

All 3 lips of PTFE seal is intact. There is rust accumulated between the lips. Make sense as its a natural trap

Ceramic Bearing

Both ceramic bearings appears to be in good shape. Seal is intact. Spins smooth by hand (even twisting a bit to feel the race surface) Spinning on v-block sounds and feels like the day it went in. There are faint clicking noises when rotating on the vblock like the day it went in. Bearing race doesn't feel like the source of all the rust.

My previous post finding a thin layer of residue on speed sensor (feels like a thin layer of paint and appears to have embedded metal particles under microscope) appears to not be the ceramic bearing seal rubber coating.

viewtopic.php?p=52682#p52682

Stator

Stator has a coat of light surface rust. Prior rebuild (3k+ miles ago) had some rust from prior leak. Cleaned it as best as I could but seems flash rust would always come back on the surface. Put a light coat of oil on it prior to assembly.

end plate bearing bore

Nothing on the end plate look abnormal, c-clip, o-ring, 2x bevel springs, metal ring, and bearing bore all looks fine.

So question is where did the rust come from?

1. stator's surface rust with light of oil eventually accumulated around the triple lip seal? Kind of hard to believe as most LDUs have a light rust dusty stator chamber when disassembled.
2. seal eventually ate away at the coolant shaft surface?
3. some other part of coolant system ( pumps etc) self destructed and introduced metal particles in the coolant?

At a loss on where this rust could have come from. I guess will be seeking either spray metal coolant shaft repair or SKF speedi-sleeve with with SKF FKM seal or a PTFE coated V lipped seal.

[Boxster EV]

Do you have the correct coolant? Incorrect coolant or mixture will certainly corrode steel components.

I’m still on my SKF seal BTW.

[howardc64]

Do you have the correct coolant? Incorrect coolant or mixture will certainly corrode steel components.

I�m still on my SKF seal BTW.

Interesting idea. I used Valvoline G48 concentrate (mixed down to 50/50 with purified water - not distilled) Probably only 2 qt is added from what was lost. G48 is the spec and what everyone seems to use.

IMG_0649.jpeg

But certainly by looking at the rust particle pattern. Downside of a multi-lipped seal is if any particles gets trapped in its interior chamber between the lips will stay there and continue to damage the shaft surface. I wonder if this is the reason Tesla went away from it? Looking at custom EV builder's effort, any LDUs that has sat idle for a long time seems to have developd a rusty coolant shaft surface. So clearly, shaft surface doesn't even like sitting in the coolant for long idle periods.

I guess another potential is the seal cage itself but I'd imagine thats stainless.

@dzolotnyuk ( post link viewtopic.php?p=46191#p46191 ) is also running the SKF FKM seal I sent him ( HMSA10 V I believe with excluder lip) with speedi-sleeve. He is probably at 10k miles now. Didn't report any problems but I'm not sure he checks speed sensor all that often. Did you use HMSA10 V or HMSAV5 (no excluder lip)?

Also what did you use to seal between speedi-sleeve and shaft?

Thanks

[Boxster EV]

Interesting idea. I used Valvoline G48 concentrate (mixed down to 50/50 with purified water - not distilled) Probably only 2 qt is added from what was lost. G48 is the spec and what everyone seems to use.

IMG_0649.jpeg

But certainly by looking at the rust particle pattern. Downside of a multi-lipped seal is if any particles gets trapped in its interior chamber between the lips will stay there and continue to damage the shaft surface. I wonder if this is the reason Tesla went away from it? Looking at custom EV builder's effort, any LDUs that has sat idle for a long time seems to have developd a rusty coolant shaft surface. So clearly, shaft surface doesn't even like sitting in the coolant for long idle periods.

I guess another potential is the seal cage itself but I'd imagine thats stainless.

@dzolotnyuk ( post link viewtopic.php?p=46191#p46191 ) is also running the SKF FKM seal I sent him ( HMSA10 V I believe with excluder lip) with speedi-sleeve. He is probably at 10k miles now. Didn't report any problems but I'm not sure he checks speed sensor all that often. Did you use HMSA10 V or HMSAV5 (no excluder lip)?

Also what did you use to seal between speedi-sleeve and shaft?

Thanks

This is the seal I used:

https://simplybearings.co.uk/shop/produ ... CCEALw_wcB

It did leak at high RPM at circa 3000k miles however I had an issue with my cooling loop (damaged / distorted hose) so I think the pump pressure was pushing too hard on the seal. It does still weep a little but hardly anything since. I’m on about 15,000 miles now.

I used G48 coolant ready mixed (not concentrate).

I just used a thin layer of reizosil gasket maker under the speedy sleeve.

[jrbe]

At a loss on where this rust could have come from. I guess will be seeking either spray metal coolant shaft repair or SKF speedi-sleeve with with SKF FKM seal or a PTFE coated V lipped seal.

PTFE doesn't absorb much moisture, that's likely out.

The multiple lips must have trapped moisture and maybe contaminants between them.

Did you clean it with chlorinated brake clean or other spray before assembly? The cooling effect from the spray can cause condensation to form on the surface. May have been chemical residue too that got trapped between the lips.

I don't think a multiple lip seal is a good idea here. If one is used you could consider a quality oil or grease (PTFE compatible) between the lips.

[asavage]

The thing I don't like about the trapped-moisture-between-lips-caused-rust-there theory is that there is a finite amount of oxygen that can be trapped, and rusting should cease once that oxygen has been depleted by . . . oxidation.

The amount of rust I see seems inconsistent with trapped moisture . . . but the rust got there somehow (formed somehow) and I have no theory on how.

[howardc64]

PTFE doesn't absorb much moisture, that's likely out.

The multiple lips must have trapped moisture and maybe contaminants between them.

Did you clean it with chlorinated brake clean or other spray before assembly? The cooling effect from the spray can cause condensation to form on the surface. May have been chemical residue too that got trapped between the lips.

I don't think a multiple lip seal is a good idea here. If one is used you could consider a quality oil or grease (PTFE compatible) between the lips.

After sanding the seal shaft surface with 600->1500 grit, I cleaned it with acetone. Probably another few weeks went by before I assembled and the surface was perfectly clean and shiny at assembly (I recall cleaning it with acetone again probably an hour before seal assembly) Didn't use any kind of lube on assembly. This is identical to Johan's effort although he only sanded a thin strip where shaft showed a whitish coating (presumably silicate)

The rust pattern is quite interesting... it appears to be ONLY between the 3 seal lips and 2 internal seal chambers. No rust outside of the seal at all. If there was a protective coating on the shaft, it would have been sanded off outside of the seal towards the shaft opening where it shows no rust. Anyway, quite the mystery. Also no rust on the shaft surface immediately beyond the seal, not inside of the coolant shaft. No rust anywhere else.

But yes, the trapping mechanism of multi-lipped seal seemingly is a possible concern.

[howardc64]

Heat signature inside coolant tube where Seal rides on the outside.

There is heat signature inside of the coolant shaft where the PTFE seal rides. All of these shaft will show a whitish coating inside the hallow shaft. There is a band inside where PTFE seal rides on the outside. Don't think its so much heat the steel blued. Rather, probably just heat so the whitish coating doesn't form. Note the rust has been mostly cleaned off in the pic.

IMG_0654.jpeg

Found a pic from the prior rebuild 3k miles ago. Didn't focus in on this area but also appears to have a heat signature although maybe less prominent? (leaking single lip PTFE seal) Note the pic was to illustrate re-greasing the ceramic bearings so shown with the bearing seal removed.

IMG_2802.jpg

Leak will enter stator even with coolant manifold drain

My outer ceramic bearing was stuck to the end plate. The rusty liquid leaking from the multi-lipped seal chamber got behind the o-ring in the bearing bore (at the lowest spot) rusting the bearing in place. At this point there is no blockage to the stator.

IMG_0655.jpeg

Also found tiny bit of coolant residue on lowest spot on inverter + casing. I thought I had cleaned it pretty well on rebuild 3k miles ago. While it was impossible to clean off all the corrosion marks on the casing. I likely would have cleaned the inverter controller connection pretty well. Just more residue than I was expecting. Perhaps the stator still had moisture from prior leak when assembled on prior rebuild. Maybe latest rusty shaft coolant seal leak is the contributor. Don't really know. It isn't very much corrosion but tiny bit. I didn't put epoxy to seal off bus bar tunnel on prior rebuild.

IMG_0651.jpeg

[jrbe]

The thing I don't like about the trapped-moisture-between-lips-caused-rust-there theory is that there is a finite amount of oxygen that can be trapped, and rusting should cease once that oxygen has been depleted by . . . oxidation.

The amount of rust I see seems inconsistent with trapped moisture . . . but the rust got there somehow (formed somehow) and I have no theory on how.

Agreed. But if someone hit a shaft with brake clean, didn't notice moisture build up from the cooled down surface that attracted condensation, then quickly assembled the seal they could have trapped water and chlorine between the lips (why I asked.)

There's the questions of how much was trapped at assembly, how much was trapped from break in, then how much from normal / abnormal weepage. Howard64 mentioned his prep steps,

After sanding the seal shaft surface with 600->1500 grit, I cleaned it with acetone. Probably another few weeks went by before I assembled and the surface was perfectly clean and shiny at assembly (I recall cleaning it with acetone again probably an hour before seal assembly) Didn't use any kind of lube on assembly.

so likely only humidity was trapped at assembly. That leaves normal weepage and break in leaks. Break in leaks can be a surprising amount and should not be overlooked. It's a big part of why I don't think a multi lip seal is ideal or a long term solution.

Heat signature inside coolant tube where Seal rides on the outside.

The white stuff inside may have formed or dissolved somewhat from the localized seal friction / heat.

Glysantin® G48® is an engine coolant concentrate based on ethylene glycol that needs to be diluted with water before use. Glysantin® G48® contains a corrosion inhibitor package based on salts of organic acids and silicates (Hybrid Coolant). Glysantin® G48® is free of nitrites, amines and phosphates.

White stuff is likely silicates or salts.

New seals need some time to wear in. Even when broken in they can leak slightly. Either / both would mean trapped coolant between the multiple lips. These seals are spinning very fast and are large for the speeds they run at (very high surface speeds.) Could have boiled & broken down any coolant that was trapped between the lips and left gnarly, decomposed stuff behind to attack the steel. Add to this theory weepage of coolant through the seal "refilling" the process.

There is heat signature inside of the coolant shaft where the PTFE seal rides. All of these shaft will show a whitish coating inside the hallow shaft. There is a band inside where PTFE seal rides on the outside. Don't think its so much heat the steel blued. Rather, probably just heat so the whitish coating doesn't form. Note the rust has been mostly cleaned off in the pic.

Steel will blue at temperatures that both should have melted the seal, boiled, and broken down the coolant. Might be a leftover from heat treatment. Coolant breakdown chemicals could be responsible for the bluing. I do think there's a strong possibility heat had a role in breaking down the trapped (leaked) coolant between the lips.

Did you use a vacuum to fill the system? I wonder if there's a bunch of air pockets in these areas.

IMG_2802.jpg

Leak will enter stator even with coolant manifold drain

My outer ceramic bearing was stuck to the end plate. The rusty liquid leaking from the multi-lipped seal chamber got behind the o-ring in the bearing bore (at the lowest spot) rusting the bearing in place. At this point there is no blockage to the stator.

For the the added drain hole, is there a way for air to enter above a leak to avoid vacuum holding any leaked coolant in there?
Also, the drain hole should be large enough in ID to avoid meaningful capillary action - holding the liquid in.

[howardc64]

Agreed. But if someone hit a shaft with brake clean, didn't notice moisture build up from the cooled down surface that attracted condensation, then quickly assembled the seal they could have trapped water and chlorine between the lips (why I asked.)

There's the questions of how much was trapped at assembly, how much was trapped from break in, then how much from normal / abnormal weepage. Howard64 mentioned his prep steps,
so likely only humidity was trapped at assembly. That leaves normal weepage and break in leaks. Break in leaks can be a surprising amount and should not be overlooked. It's a big part of why I don't think a multi lip seal is ideal or a long term solution.



The white stuff inside may have formed or dissolved somewhat from the localized seal friction / heat.



White stuff is likely silicates or salts.

New seals need some time to wear in. Even when broken in they can leak slightly. Either / both would mean trapped coolant between the multiple lips. These seals are spinning very fast and are large for the speeds they run at (very high surface speeds.) Could have boiled & broken down any coolant that was trapped between the lips and left gnarly, decomposed stuff behind to attack the steel. Add to this theory weepage of coolant through the seal "refilling" the process.


Steel will blue at temperatures that both should have melted the seal, boiled, and broken down the coolant. Might be a leftover from heat treatment. Coolant breakdown chemicals could be responsible for the bluing. I do think there's a strong possibility heat had a role in breaking down the trapped (leaked) coolant between the lips.

Removed Protective Surface Finish Possible Source?

Found this video that might provide a hint. This Croatia EV rebuilder re-chrome the shaft before sanding for the finish. The rest of the video is about making their own stator (they say Tesla reman stator isolation quality is poor)



My LDU was a reman and I prep the shaft surface with light sanding (didn't dare to remove too much material). It is possible Tesla's reman didn't refinish the shaft surface. In general, Tesla reman quality has been poor. They likely just find 3rd parties on major market continents and get it working for warranty replacements. My reman LDU from Tesla had a whine during regen loading. Found the primary shaft counter bore bearing spun and locked in the bore during my rebuild. Have also read Tesla's reman battery packs with 100mV imbalance, high miles and high fast DC charge % in Germany ( https://teslamotorsclub.com/tmc/posts/7357046/ ). EU rebuilds seems worse than US (Tesla's home market)

Anyway, just a possible explanation. I would guess a single lipped seal likely wouldn't see this problem even if shaft finish is gone. Wet side has ample coolant to cool. Dry side leaks migrate quickly away from the seal. Multi-lipped will trap leaks in the chamber under constant high heat.

In all my seal studies (Johan and I did quite a bit of reading/researching on all kinds of seals) They all leak including PTFE (even after initial break-in even with thicker oil). But not much published info on how multi-lip PTFE seal actually work, does leak get trapped in the chamber in between? Is there back pressure to help reduce leak? All detailed studies on PTFE sealing is with oil (higher boiling point) rather than coolant). Univ of Stuttgart has 2+ decade of research on single lipped PTFE sealing oil. They've done much work on lip surface pumping aid for leak reduction.

Did you use a vacuum to fill the system? I wonder if there's a bunch of air pockets in these areas.

Didn't do this because Tesla's multi pump + valve design makes it a mystery on how to bleed the coolant system without their security locked diag tool. I just filled it and filled it few times initially as the reservoir level lowered (also puked some out). It is sitting at the MIN mark (I think thats where it was after initial set of top offs) just before this LDU removal at 3-4k miles post rebuild/coolant top-offs.

For the the added drain hole, is there a way for air to enter above a leak to avoid vacuum holding any leaked coolant in there?
Also, the drain hole should be large enough in ID to avoid meaningful capillary action - holding the liquid in.

Drain hole

This is on the dry side and has probably 2+mm ID with a clear drain line and see rusty residue in it. So pretty sure its draining. However, it appears the likely thicker rusty liquid doesn't drain as easily

- All around the reluctor chamber as it spun the rusty liquid all around.
- bottom of speed sensor chamber
- bottom of outer ceramic bearing race on the stator side of the o-ring
- In between the coolant seal of course

IMG_0656.jpeg

On the question if any air can enter above leak. It would have to go through the seal. I suppose air is even thinner than coolant and since we tapped a drain port, ambient air pressure will enter the reluctor chamber (I didn't seal the end of drain line, maybe should have? This is probably source of O2 as @asavage was wondering where it came from). If any vacuum pressure exist on the wet side (when coolant is cooled?), seems like air can get pulled in.

Another reference point is @dzolotnyuk ( post link viewtopic.php?p=46191#p46191 ) effort. He didn't RTV the manifold (pulled it many times, reasoned with drain port, no use sealing it. @Johan did suggest helpful in case of flooding) He is on speedi-sleeve + SKF FKM seal (HMSA10 V - single coolant V shaped lip, excluder lip sized to not touch speedi-sleeve) and hasn't reported any problems in the 1 year since rebuild. So even O2 entering reluctor chamber likely not an issue for single lipped seals (I don't count excluder lip that has air gap to shaft surface a sealing lip)

[jrbe]

Removed Protective Surface Finish Possible Source?


Anyway, just a possible explanation. I would guess a single lipped seal likely wouldn't see this problem even if shaft finish is gone. Wet side has ample coolant to cool. Dry side leaks migrate quickly away from the seal. Multi-lipped will trap leaks in the chamber under constant high heat.

The outer edge of the motor shaft looks ok (no rust.) I don't think it would be a problem if it's the right surface finish with good coolant and no traps.
It is possible to have the surface finish too smooth to be ideal for the seal.

I don't doubt the reman quality isn't good. Everyone is battling for low cost and usually end up cutting necessary corners to achieve their cost targets.

(vacuum coolant system before fill)
Didn't do this because Tesla's multi pump + valve design makes it a mystery on how to bleed the coolant system without their security locked diag tool.

That's what's really nice about using vacuum on a coolant system to fill it. All the air is gone, you can check for leaks before filling it. Then if it doesn't leak air in while in vacuum, it uses the vacuum in the system to suck the coolant in and leaves no trapped air. As long as there's a single path through the coolant it will get where it needs to be.
There is a danger of the vacuum destroying something though (usually about to go anyways though.) I'm not sure if it's an issue to use on Teslas or not.

Drain hole

This is on the dry side and has probably 2+mm ID with a clear drain line and see rusty residue in it. So pretty sure its draining. However, it appears the likely thicker rusty liquid doesn't drain as easily.

A few things here. A 2mm drain can cause capillary action that can hold a shallow puddle of coolant up. Also, where the drain hole is, it looks like the centering lip of the water manifold blocks a lot of the hole which could be more of a restriction, might kick off the start of the puddle.

Might be worth doing an experiment with only the motor cover and coolant manifold bolted together with the drain assembly in place and oriented as it would be in the car. Add coolant where it should drain (dry side as you call it) and see how much you need to add until it dumps. I think the results will be surprising (more liquid than you'd expect.) This also isn't including vacuum in there that could further up the level until it dumps.

On the question if any air can enter above leak. It would have to go through the seal. I suppose air is even thinner than coolant and since we tapped a drain port, ambient air pressure will enter the reluctor chamber (I didn't seal the end of drain line, maybe should have? This is probably should of O2 as @asavage was wondering where it came from). If any vacuum pressure exist on the wet side (when coolant is cooled?), seems like air can get pulled in.

The air I asked about was to allow coolant to drain out. Meaning that trigger wheel void area is able to easily suck air in from above the coolant that you want to drain. If the water manifold is siliconed in, it likely can't get air in the dry side unless it shares a breather / passageway. The vacuum of the coolant trying to drain can also hold the coolant up further, especially with a small drain ID.
The other trapped air was in the cooling system which could allow hot spots.
You want the drain line open or the leak can't escape.

The HMSA10 V (SKF) seal is a fluoro rubber and has a 3480 rpm rating (surprisingly low because of the large diameter / high surface speed.) There's likely some safety /wiggle room above that but it's well above is rated rpm here. It might work well for a while but I doubt it would do 80k+ or survive many high rpm cycles.

muehlpower's seal looks like a great option to me.

[asavage]

The air I asked about was to allow coolant to drain out. Meaning that trigger wheel void area is able to easily suck air in from above the coolant that you want to drain. If the water manifold is siliconed in, it likely can't get air in the dry side unless it shares a breather / passageway.

The assembly has a vent, though it's on the inverter side. Howard didn't seal (RTV or other compound) the inverter-to-stator passage, so the dry side has a path to the outside via the case vent, and no vacuum is formed in the area where the rotor shaft leaks.

Johan did a great job of explaining the venting:

Tesla LDU Venting

[asavage]

Deciding to leave the retaining compound out isn't a great idea. The aluminum case expands much more than the steel in the bearing as they heat up. It can get loose / spin if you skip it. In fact, heating the case is the easy way to get stuck bearings out typically.

To clarify again, Howard found what appeared to be retaining compound in the counterbore's corners, and I advised him to not intentionally place compound there, as it does/would do nothing productive there.

viewtopic.php?p=56822#p56822

[asavage]

As I have already written, I am in negotiations with a seal manufacturer in Germany. He sent me an interesting draft. I have pointed out that a Speedi Sleeve may be used. He also takes into account the slightly larger diameter and the limited length.
He also has reservations about using Loctite because of the poor heat dissipation. I did some googling and came across this glue.
https://www.sepa-europe.com/wp-content/ ... 000010.pdf

From that PDF, the HERNON 746 SET THERMAL CONDUCTICE [sic] ADHESIVE requires to not be mixed, but one component ("adhesive") placed on one workpiece, and the other component ("hardener") placed on the other workpiece. They are not allowed to be mixed, and when they are placed together, the working time is 15-30 seconds.

I cannot imagine an assembly method for installing the Speedi-Sleeve where the sliding action of installation leaves any significant amount of mixed compound where it is needed. Whatever component is placed on the rotor will be wiped off toward the rotor middle, and all of the component that is placed inside the sleeve will similarly be wiped off on the rotor end.

While a two-component thermally conductive adhesive may work well, I can't think of using one that doesn't allow pre-mixing.

Loctite/Bergquist have several competing products of this type, but I haven't waded through their datasheets adequately to comment on suitability for this purpose.

[howardc64]

The outer edge of the motor shaft looks ok (no rust.) I don't think it would be a problem if it's the right surface finish with good coolant and no traps.
It is possible to have the surface finish too smooth to be ideal for the seal.

I don't doubt the reman quality isn't good. Everyone is battling for low cost and usually end up cutting necessary corners to achieve their cost targets.

I've seen enough Tesla new car design and recall engineering to have no confidence. For reman, I think we'd be lucky to get summer interns at HQ leading reman effort as any experienced people chasing stock options have left and/or onto the new cars in silicon valley employment culture. Even my first Tesla SC mechanic left for Rivian for fresh stock options haha. Then there is the question of 3rd party rebuilders. Who they are and QC reputation. Its quite interesting we still don't know who they are as Tesla's big business leverage keeps them all quiet without releasing any info. No one from Tesla reman operations are chiming in anywhere. Sealed lips (no pun intended) probably in the contract.

The HMSA10 V (SKF) seal is a fluoro rubber and has a 3480 rpm rating (surprisingly low because of the large diameter / high surface speed.) There's likely some safety /wiggle room above that but it's well above is rated rpm here. It might work well for a while but I doubt it would do 80k+ or survive many high rpm cycles.

muehlpower's seal looks like a great option to me.

FKM seal (HMSA10 V and HMSA5) are both also weak to polar molecules such as hot water/steam. But we do have 2 data points of it operating at least past 10k miles. Given all seals will leak against just about any media, 80k dry is impossible. Univ of Stuttgart's pumping aided single lip PTFE seal with oil leaks like 1 drop an hour even after break in.

@muehpower's PTFE seal is quite interesting in design. Tesla's lipped PTFE seal depends on a curved lip to apply pressure. Curvature depends on seal/shaft geometry and material property. GFD's seal surface is on a PTFE beam while the contact surface is a perfectly flat mating region (2?mm cross section) with a garter spring. This is much more controlled designs to provide pressure. I think this controlled design is what allows it to be so adaptive to speedi-sleeve and no sleeve applicaitons.

The following 2 are key parameters from my understanding of PTFE seals

- Shaft surface need fairly low roughness finish (I think multiple 10s of Ra) but not perfectly smooth. PTFE seal need to transfer a layer of PTFE material to the shaft and its this material against the remaining PTFE seal lip that does the sealing. This is quite different than elastomer (NBR & FKM) seal's mechanism (compressed elastomer hydroplane over trapped fluid pockets on tiny surface potholes) Anyway, PTFE seal manufacturers all note surface roughness is fairly critical for longevity.

- Contact cross section width of PTFE seal lip is what gives it a lower heat density. A classic V shaped elastomer seal lip will have about 0.25mm contact cross section where as PTFE lips will have about 2mm. So a 10x factor in contact area that contributes to better heat density besides the more heat tolerant PTFE material

[asavage]

Fried IGBTs
Finally, I've seen this LDU->1970s American Muscle car build that fired an IGBT. Author claims can happen when power drops out while driving. I'm assuming this uses non Tesla control board that most custom EV builders are using.

Opening the HV power circuit on an induction motor whilst the unit is drawing any significant current and while it is spinning will fry the IGBTs in the inverter. It happens frequently, and we hear a story about this every month or so here. "Opening the HV power circuit" could mean hitting an E-stop switch, an unintended opening of the main battery pack contactors, or a fuse blowing. They all come to the same end: the rotating AC field and IGBTs are doing a delicate dance with lots of energy moving, and when the path to the pack is removed, the inverter's DC caps can't handle the power in play, they let go, and then the voltage spikes take out the IGBT gates and it's all over.

I don't know what the situation is with a "stock" LDU when this happens.

[howardc64]

The assembly has a vent, though it's on the inverter side. Howard didn't seal (RTV or other compound) the inverter-to-stator passage, so the dry side has a path to the outside via the case vent, and no vacuum is formed in the area where the rotor shaft leaks.

Johan did a great job of explaining the venting:


Telsa_LDU_Venting_01b.png

While I didn't seal the bus bar tunnels between motor and inverter. I did JB weld the speed sensor vent hole. So theoretically the only path air/liquid pathway between stator and reluctor chamber is the orange o-ring for the outer ceramic bearing bore AND through the ceramic bearing seal+ball+cage itself.

In any case, I'm guessing the reluctor chamber drain port is easily the best source of new oxygen.

To clarify again, Howard found what appeared to be retaining compound in the counterbore's corners, and I advised him to not intentionally place compound there, as it does/would do nothing productive there.

viewtopic.php?p=56822#p56822

I should clarify what I found on my LDU's counter bore bearings and info from others.

Primary Shaft Counter Bore Bearing - SKF 6207

Early remaned (and maybe also initial production) primary shaft counter bore bearing (SKF 6207) didn't have retaining compound from Tesla. Mine spun in the bore likely resulting in the regen whine. We've seen a later reman LDU have retaining compound here.

Per @asavage's suggestion, I froze a 6207 bearing, cleaned the outer surface with acetone, lined the cleaned bore with retaining compound and the bearing just gravity sled slowly into the bore. Was very easy. Regen whine gone after rebuild (got other speed related whines instead, will be openning the gearbox for inspection since LDU is pulled again for the rusty coolant seall shaft)

Intermediate Shaft Counter Bore Bearing - FAG X-life RNU2207E TVP

The intermediate shaft counter bore bearing (FAG X-life RNU2207E TVP) roller bearing) was another matter. We only found between 1/2" to 1"+ of red locktite on the side of the outer race. Maybe just to keep it there while vertically drop the counter bore side of the case during assembly. This bearing barely fit into the bore on a clean surface and easily jams with slightest tilt. I didn't dare to put in retaining compound and have it jam during insertion. Maybe there is a safe easy way. I'm just too inexperienced with bearings to execute these time limited temperature based assembly method without error.

As far as I know, DIY rebuilders are just repeating Tesla's 1/2-1mm red locktite at the edge of the outer race. It would be good to have a easy foolproof way of inserting this bearing. Probably best to heat the counter bore casing which requires experience AND pulling the inverter (easy to mess up the coolant o-ring on reassembly)

Differential shaft counter bore bearing

No evidence of retaining compound and the bearing is pressed into the differential assembly so no easy way to put retaining compound in the bore without it dropping while vertically dropping counter bore casing during assembly. Seems like all DIYers aren't applying anything here.

[howardc64]

From that PDF, the HERNON 746 SET THERMAL CONDUCTICE [sic] ADHESIVE requires to not be mixed, but one component ("adhesive") placed on one workpiece, and the other component ("hardener") placed on the other workpiece. They are not allowed to be mixed, and when they are placed together, the working time is 15-30 seconds.

I cannot imagine an assembly method for installing the Speedi-Sleeve where the sliding action of installation leaves any significant amount of mixed compound where it is needed. Whatever component is placed on the rotor will be wiped off toward the rotor middle, and all of the component that is placed inside the sleeve will similarly be wiped off on the rotor end.

While a two-component thermally conductive adhesive may work well, I can't think of using one that doesn't allow pre-mixing.

Loctite/Bergquist have several competing products of this type, but I haven't waded through their datasheets adequately to comment on suitability for this purpose.

So we have

@johan and GFD (experienced PTFE seal designer) with concerns on thermal transfer of speedi-sleeve
@Boxter EV and @dzolotnyuk both running speedi-sleeve with RTV and @asavage thinks any filler will just be scraped off after sleeve install

SKF's speedi-sleeve installation info suggest sleeve is self-sealing unless heavier wear surface which requires epoxy filler.

https://www.skf.com/us/products/industr ... edi-sleeve

I guess in reality, probably not much filler remain post install? @Boxter EV and @dzolotnyuk haven't burnt up their SKF FKM seal instantly

[asavage]

When you're installing a Speedi-Sleeve, it's to correct surface imperfections that would cause a seal to not work well. So I assume that the sleeve will not have great contact with the shaft, and will have the worst contact in exactly the area where you would want the most contact!

I'm not saying that all of any adhesive would be wiped off, only that this particular two-part-without-premixing product . . . can't work here. We need a product that has adhesive properties but also thermal transfer properties, and one that can be applied ready-to-go on the shaft, prior to pressing on the Speedi-Sleeve. The leading edge of the sleeve will push some un-mixed component out of the area it's needed, and the rotor's end will push almost all of it's component out of the sleeve. Never will the twain mix.

Put another way (beating this to death), whatever compound we apply needs to be applied to the shaft, not the sleeve, because the shaft has the grooves/divots/below surface places that will hold the compound. The sleeve doesn't, and anything you apply to the ID of the sleeve is useless, because it will all be pushed off during assembly.

The Hernon 746 can't be pre-mixed, and due to the installation method required for the Speedi-Sleeve, it won't mix during assembly; therefore, both its thermal conductive and adhesive properties would be either non-existent or sub-optimal.

[howardc64]

Another concern for speedi-sleeve is how to avoid scoring the PTFE seal surface during seal+manifold install as the lip slides over the sharp sleeve edge.

@WimV did an awesome job of machining 2x speedi-sleeve onto the shaft. ( viewtopic.php?p=46364#p46364 ) But if you look close at the image, there are sharp edges along the bevel opening of the coolant shaft. WimV got a leak on speed sensor within 300mi with Ceimin triple lipped seal. Given Johan and I survived beyond 3k miles with the same seal without speed sensor leak evidence. I'm assuming @WimV's effort scored the PTFE seal lip on the way in during install.

GFD's PTFE seal will have this same problem as any other PTFE seal. What is necessary is probably one of 2 things

- using a filler to bevel that sharp speedi sleeve edge and polish it down smooth. But will be challenging since don't want to change the surface of the speedi-sleeve right behind the edge. Probably best done on a lathe with tight control?

- custom sleeve with a bevel. Sleeve would need to be longer than the SKF to bevel over existing shaft bevel and still cover enough shaft to mate against the seal lip.

@muehlpower : Do you think GFD can also source a custom sleeve and proper thermal transfer filler? Then it'd be a complete solution for any shaft situation.

[jrbe]

To clarify again, Howard found what appeared to be retaining compound in the counterbore's corners, and I advised him to not intentionally place compound there, as it does/would do nothing productive there.

viewtopic.php?p=56822#p56822

As far as I know, DIY rebuilders are just repeating Tesla's 1/2-1mm red locktite at the edge of the outer race. It would be good to have a easy foolproof way of inserting this bearing. Probably best to heat the counter bore casing which requires experience AND pulling the inverter (easy to mess up the coolant o-ring on reassembly)

There are wicking grade retaining compounds. Might be what some are seeing in odd spots on bearing bores.

Another concern for speedi-sleeve is how to avoid scoring the PTFE seal surface during seal+manifold install as the lip slides over the sharp sleeve edge.
...snip...
GFD's PTFE seal will have this same problem as any other PTFE seal. What is necessary is probably using a filler to bevel that sharp speedi sleeve edge and polish it down smooth. But will be challenging since don't want to change the surface of the speedi-sleeve right behind the edge. Probably best done on a lathe with tight control?

Could spin the rotor and use an angled dremel spinning the right way with a soft wheel to add a lead in. A lathe would be nice too.

When you're installing a Speedi-Sleeve, it's to correct surface imperfections that would cause a seal to not work well. So I assume that the sleeve will not have great contact with the shaft, and will have the worst contact in exactly the area where you would want the most contact!

I'm not saying that all of any adhesive would be wiped off, only that this particular two-part-without-premixing product . . . can't work here. We need a product that has adhesive properties but also thermal transfer properties, and one that can be applied ready-to-go on the shaft, prior to pressing on the Speedi-Sleeve. The leading edge of the sleeve will push some un-mixed component out of the area it's needed, and the rotor's end will push almost all of it's component out of the sleeve. Never will the twain mix.

Put another way (beating this to death), whatever compound we apply needs to be applied to the shaft, not the sleeve, because the shaft has the grooves/divots/below surface places that will hold the compound. The sleeve doesn't, and anything you apply to the ID of the sleeve is useless, because it will all be pushed off during assembly.

The retaining compound or thermal adhesive should be put on both pieces then cleaned up after assembly. ID & OD application will roll a bead on each leading edge as they slide together. Both gives a chance for it to fill the gaps while assembling together. Its messier but will very likely work better.