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Thank you howardc64 for the wealth of knowledge you have with the LDU. I've been reading your posts nonstop in the forum, very informative. I still have so much to read.Interesting access method! Luckily LDU HV cables run along the other (passenger) side
I know the motivation to not remove the LDU. But couple of thoughts
Not too hard with 2 floor jacks, 8' 4x4 strong wooden beam and a cheap motorcycle jack
See post #91 towards the bottom "Jacking Up the Rear to Put on Stand" AND post #10 ) Followed by a cherry picker to pull LDU out of subframe post #15. All the LDU's weight is on the stator side so center of gravity on the pull bias that direction to avoid tilting the LDU on removal (not much space with wrap around subframe and likely easy to break the weak LDU aluminum mount welds on the subframe)
Running the PTFE seal dry with a hotter rotor might not be a good idea
Reading the seal design literature. A key factor to consider is frictional heat. Few key factors
This include seal contact surface getting cooled by circulating coolant and hydroplaning over lubricating media in oil media. Without circulating media, and no shaft cooling, lips are probably going to burn up. PTFE seal material is like really hard plastic. No idea what happens to them getting cooked.
- Surface speeds (m/s) = shaft diameter x rotation speed. Most advanced rubber seals handle up to like 5-10 m/s. PTFE can do higher like 30 m/s ( SKF )
- Rotor's 30mm diameter shaft at say 7k RPM (~70mph) = 2 x pi x 15mm / 1000 x 7000RPM / 60s/min = 10m/s
- Contact cross section of the seal. Narrower (V lipped rubber seal contact ~= 0.2mm) = higher heat density. Luckily Lipped PTFE seal contact region is like 2mm cross section for a lower heat density. This is a huge factor in why they can tolerate higher surface speeds
Furthermore, on the dry side of the seal lip, unavoidable slight leak will crystalize coolant into silicate solid particles which probably act like sandpaper against the shaft.
Multi lipped seals do have a mostly dry lip on the dry facing side. But its mated against a shaft surface that is getting cooled with coolant.
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About to pull my LDU for the 3rd time this coming week and thinking about manifold mod. A few thoughts
View attachment 1013125
Also thought about tap inlet with T. Need to worry about reduced flow rate with a narrowing passage at the T. Maybe not much and is okay.
Thinking about drilling a hole on side of the manifold neck to access the coolant tunnel that runs up the neck. Manifold is not structural here so can make the drilled hole quite large. Large enough to consider the following
Connecting coolant flow to the fly over tube have lots of options and should be much easier. Can cut and connect to this tube towards the gear box. Can Tee it. RTV a blocking plate can seal the manifold coolant exit and any fly over tube back flowing into the manifold.
- Inject RTV into the tunnel, maybe seal the inlet side with JB Weld so RTV can get pressured up against a stop and squeeze into any tiny gaps at this stop.
- Offers opportunity to tap a bypass coolant channel and run it up to the fly over tube
- Or just insert a cylinder plug with RTV to seal the tunnel.
Even not routing the coolant into the fly over tube maybe okay. Entry to gearbox is 5mm diameter hole. Once inside, just combine with majority of the coolant that went through stator casing->inverter at the gearbox heat exchanger before existing the LDU ( post #139 )
Anyway, plugging the rotor coolant tunnel is the main mod challenge.
As I'm looking at the hole you cut in the trunk to access the top bolt of the manifold pipe, I can't help but wonder if one could cut a rectangular hole to gain access to the whole manifold to unbolt from above and bolt on the updated QC Charge manifold without removing the LDU? Then maybe 3D print a cover to reinstall over the rectangle hole?View attachment 1012934View attachment 1012933
Im trying to do the bypass as easy as possible by not removing the LDU. I drilled a hole on the trunk Bec there is no space around the LDU to get to the top coolant line. With the hole, the top coolant line can be easily disconnected and be connected to a line that will be connected to the tee fitting.
This is my idea for a coolant delete. I obtaiThe depth of the centre is 12mm. I hope that is deep enough.
Thanks for the advice Howard. Now I have an excuse to buy a small mill. The base of my cup is about 6mm thick, so I'll remove another 3.Might need 13-14mm deep ( post #57 pdf )Rotor also sits on a bevel washer spring so theoretically can push out a little (< 0.5mm?) on high speed right hand motion.
But yes, would be nice just to have a stainless cap in this shape where seal use to go.
Small custom PTFE seal makers will make ~5 seals in stainless cages for $500. I'd imagine even cheaper just to press cages in the right shape.
Thanks for the advice Howard. Now I have an excuse to buy a small mill. The base of my cup is about 6mm thick, so I'll remove another 3.
Z3ds:View attachment 1012934View attachment 1012933
Im trying to do the bypass as easy as possible by not removing the LDU. I drilled a hole on the trunk Bec there is no space around the LDU to get to the top coolant line. With the hole, the top coolant line can be easily disconnected and be connected to a line that will be connected to the tee fitting.
Hi nemisonic,Z3ds:
Have you been able to prototype the on-vehicle fix? Do you have any tips/tricks or parts list to share? I've been under the vehicle for a speed-sensor check and with your tip to cut access hole in body, it looks like this would be do-able after disconnecting the HV first responder's loop, and safely using heavy-duty jack-stands.
I am familiar with the QC-Charge part, and have done serious work on vehicles DIY like the LDU removal- but on ICE transmissions and transfer cases for 4x4s. That being said, I would much prefer to try this "on vehicle" fix because of how PITA factor is on this level of DIY (and $7k to Tesla SC is crummy) and we no longer live near Carlsbad, CA to ask QC Charge to do it (unless someone knows a partner in New England?).
I am already burned by a $16k battery on a 50k mile vehicle, wonder if it is worthwhile trying this fix vs. dumping the lemon.
Thanks!
Are there any shortcuts to changing the manifold? Would it be possible to drop the subframe just a little, leaving the drive motor supported in place?Did a bunch of measurements while considering speedi sleeve shaft surface reconditioning and needed to figure out where the seal lips will land.
Also calculated how deep of a cup is necessary for those looking to remove coolant tube and cap the seal bore. Looks like need to go about 15mm deep from seal bore to clear the rotor shaft comfortably by ~2mm (before any rotor axial movement per bevel washer spring (maybe 0.5mm)) and still 4mm to the shoulder below circlip for coolant passage and cup thickness. Page 1 of attached PDF
Are there any shortcuts to changing the manifold? Would it be possible to drop the subframe just a little, leaving the drive motor supported in place?