Repair of EV splined motor coupling

[MetalMonkey]

That brings back memories! I used to service and rebuild a lot of SAFT cells for aircraft batteries. I must have pressure tested thousands of those bloody vent caps.

Do you have any issues sourcing them as the last I heard they were trying to ban them?

 

[eddie49]

I did know that SAFT batteries were used in aircraft. In the vans there are four battery boxes, each with the batteries connected with pipes in a series path for top-up water. The batteries are also water-cooled. Apparently they are good for at least 2,000 cycles, which would mean about 120,000 miles.
Initially in the late 90's and early 2000's the vans were only sold to Councils and public bodies. Later a couple of hundred passed on to private owners. Mine came from Exeter Council Parks & Gardens Dept. Around five or ten years ago the 6v batteries were traded amongst EV forum members, or brought over from the EU, at about £100 each, but I have never been able to get hold of any. The dead batteries are impossible to get rid of, nobody accepts them for recycling. I had planned to upgrade my van to Lithium, but now that I have this new e-Berlingo, that may never happen...

 

[Red'n'Black]

That brings back memories! I used to service and rebuild a lot of SAFT cells for aircraft batteries. I must have pressure tested thousands of those bloody vent caps.

Do you have any issues sourcing them as the last I heard they were trying to ban them?

Cadmium is one of the banned substances under the RoHS regs, when they came into force most consumer stuff that used NiCd went over to NiMH (which is more or less a direct replacement) or lithium (which isn't).

If the batteries were a custom design for Citroën there probably won't be a NiMH equivalent, unless somebody out there knows different?

 

[eddie49]

The SAFT batteries do remind me of the NiFe cells that we used to provide power for physics experiments at school, and they have the same electrolyte. Back in 1966 as a part-time Lab Assistant one of my duties was to charge those batteries.
However, these are definitely Nickel-Cadmium. SAFT Technical Manual attached.

 

[eddie49]

I have been helping another member of the EV Forum with the repair of the splined coupling on his Peugeot "Tepee" EV, in Portugal. He is using an independent garage to inspect and fix the noisy/worn splined sleeve. The coupling side that joins the transmission is badly worn, and so is the transmission input shaft:


The garage have found a welding company that plan to cross-drill holes in the sleeve and use rosette welds to permanently fix it to the transmission shaft. He will send me photos of the welding job. I am worried that it will fry the gearbox oil seal.

 

[Seadog]

I'd say that that's a given. It's then impossible to change.

 

[Red'n'Black]

I wouldn't use anything involving heat next to an oil seal. BTDT with a knackered kickstart on a bike. It did have a self oiling chain afterwards though...

 

[Brad93]

Welding on a hardened splined shaft, not gonna end well i'm afraid

 

[Robotstar5]

If they're going to drill it, why not use roll pins instead?

 

[8ob]

I am very surprised that nobody is cutting/splining couplings in various tooth widths to compensate for this wear.

Bob

 

[bricol]

If they're going to drill it, why not use roll pins instead?

Torque.
They simply won't take it in and will shear.

Probably what the welded shaft will do anyhow.

 

[Morrisman]

Stripped gearbox input splines is a bit of a problem on certain models of BMW bike. Everybody reckoned it’s because the bike isn’t stripped in half and the splines greased every couple of years.

But, research was done and apparently a certain quantity of gearboxes were manufactured incorrectly with the locating dowels offset by 0.5mm or so, which means the spline is continually being loaded eccentrically.

Maybe someone could look into this particular EV gearbox for some similar mass production cock up?

 

[Robotstar5]

Torque.
They simply won't take it in and will shear.

Probably what the welded shaft will do anyhow.

I'd better stick to electrics

 

[Brad93]

Fretting is usually the cause of such wear, small cyclic movements over time

 

[Bornfree]

Ford 40 series tractors had a similar set up on the drive shaft to the front axle. Because the coupling and differential pinion were both knackered I welded it. But the pinion stuck out further so I had a hose running water near the seal whilst I welded it.

 

[eddie49]

Fretting is usually the cause of such wear, small cyclic movements over time

The electric motor shaft and the motor end of the splined sleeve are still perfect:

The motor is made in Japan by Meiden. The transmission is made by GKN. I had assumed that the fault is caused by incorrectly-specified material for the transmission input shaft.

 

[Brad93]

The electric motor shaft and the motor end of the splined sleeve are still perfect:
View attachment 456397View attachment 456396
The motor is made in Japan by Meiden. The transmission is made by GKN. I had assumed that the fault is caused by incorrectly-specified material for the transmission input shaft.

That red/brown dust is fretting

 

[Misterg]

I had assumed that the fault is caused by incorrectly-specified material for the transmission input shaft.

It's just a crap arrangement (IMHO). There should be some sort of coupling there that can accommodate minor misalignment - that splined sleeve will always move and fret unless the shafts are in perfect alignment - and remain so when the transmission is loaded.

 

[bricol]

Looks dry - most splined couplings seem to be assembled with a lubricant which would help prevent the fretting issue.

Any misalignment will lead to accelerated wear.

Is there any instruction, or indication, which way round the coupling is to be fitted? One might assume it is fitted to one side first, the other then slid into it - so one shaft may have a looser tolerance to allow an easier assembly? Always going to be some backlash in there, and small movements will wear into larger.

On/off cycling of the load will accelerate wear - such as accelerating, lifting off etc - inertia mis-match between motor and drivetrain won’t help.


Think it’s been mentioned before, maybe even by me, torque from an electric motor is instant - from an ICE it isn’t. Theory is always good, but nothing beats the real world - maybe the testing being performed in real world driving will help improve newer versions

 

[Jelly_Sheffield]

It's just a crap arrangement (IMHO). There should be some sort of coupling there that can accommodate minor misalignment - that splined sleeve will always move and fret unless the shafts are in perfect alignment - and remain so when the transmission is loaded.

Agreed.

A friend of a friend is building an electric motorbike using the motor out of a Mitsubishi Outlander, inspired by meeting this chap (30 minute video at bottom of page), who has done just that already.

After some frustrating results with prototype rigid couplers, he built a torque smoothing coupler that is effectively a dog clutch with very beefy springs between the dogs, permanently clamped between two thrust bearings that are preloaded by a two-part housing.

Which is not a million miles away from the elastomeric and slit-sleeve flexible couplers used on industrial motors to correct for minor shaft misalignment...

You have to wonder how it is that Stellantis believed they didn't need to address an issue that is taken as a given during the design process for rotating equipment by pretty much every other industry that uses electric drives in high starting torque and high RPM applications.