Statorade maintenance, time vs miles

[E-HP]

My Statorade has run dry, or at least that's what the evidence is pointing to. I added Statorade to my hub two years ago, and it's been running nice and cool until a few weeks ago. That's when I started noticing the motor getting hot, even on flat ground, when horsing around with some spirited riding. It was hitting the high 80Cs, when normally it would stay in the lower 70Cs even when mashing on the throttle a lot. I also noticed the motor getting hotter more quickly on hills.

This weekend I did some offroad testing on a few trails I normally wouldn't have an issue with and my observations were confirmed. The motor was getting near the danger zone half way up hills that I would normally ride up without a problem. Additionally, it would continue to heat up after I was off the throttle (it shot up 10C is a couple of seconds). The normal behavior is that the motor cools very quickly when off the throttle, but now it cools very slowly, which to me, confirms that the Statorade is no longer working.

I reread the super long hub motor cooling thread, and a few other Statorade maintenance related threads, but it's hard to glean whether maintaining Statorade should be based on time or miles. As I mentioned, I've gone 2 years without topping off or flushing, and around 7k miles. I've decided to add Statorade to my rigorous ebike maintenance routine, which currently consists of checking the axle nuts once a month, and lubing the chain twice a year. Should Statorade be part of an annual/biannual maintenance routine or something done every 5k miles or so? Also, some threads mention flushing the old stuff out, so that would affect how to maintain it. On my old ebay motor, I had drilled and tapped a filling hole in the case, but for my current motor, I opened it and had the very satisfying experience of applying it directly to the magnets and watching them suck it up. If maintenance is just adding fluid, I'd drill and tap a fill hole.

 

[amberwolf]

Speculation:

My guess is it isn't miles or time directly, but a combination of those vs how well sealed a motor is, the temperatures it reaches, and the design of things like it's laminations and windings, whether or not the magnets are glued to the rotor and how securely (and with what), etc.

(I also think it wouldn't be miles, but rather rotations of the motor, which will depend on the speeds travelled and the motor RPM and how long...with most DD hubmotors they are about the same size, so same RPM for the same speed and wheelsize, but since speed and wheelsize vary, miles probably isn't directly comparable).

If the magnets are securely glued to the rotor with no gaps for statorade to migrate into, and use a glue it can't dissolve or penetrate or bond to, then there would be less loss of SA.

If the laminations are loosely bound, there is more gap for the SA to wick into, but it's possible this might actually impede it's migration vs closelypacked lams because of surface tension, etc. (I don't know SA's properties in that regard).

If the windings are packed closely enough to the stator tooth top, perhaps some of the SA carrier could also migrate into those.

If a motor is not well-sealed the carrier could migrate out the cover edges, etc., and if the sealant used can be penetrated by or reacted with the carrier, there will be more loss.

Etc.

 

[nicobie]

Why not drill and tap a hole and add some SA and see what happens.

Maybe all the metal/magnetic crap that has accumulated over the years is sticking to the SA and impeding heat transfer?

 

[E-HP]

Speculation:

My guess is it isn't miles or time directly, but a combination of those vs how well sealed a motor is, the temperatures it reaches, and the design of things like it's laminations and windings, whether or not the magnets are glued to the rotor and how securely (and with what), etc.

I guess if I maintain the same riding habits/pattern, then time vs distance works out to be the same. I'm curious to know what actually happens in the motor, since the ferreous particles must continue to accumulate on the magnets. Maybe they get matted down in gunk left over from the carrier fluid, so they no longer bridge the gap with the stator.

Why not drill and tap a hole and add some SA and see what happens.

Maybe all the metal/magnetic crap that has accumulated over the years is sticking to the SA and impeding heat transfer?

OK, I'm trying that. Least amount of downtime, and I can reverify and compare with the temp data before things started to degrade. I can do a visual inspection over the winter.

Of course I got a few extra allen socket set screws (plugs) last time, and stored them with the tap...it will be a miracle if I can find them LOL.

 

[scianiac]

I always kinda assumed that the carrier fluid evaporates over time and that is spend up by it being warmed up fairly often although I assume that's pretty much the same result as the carrier leaking out like amberwolf mentioned. Which also makes me wonder if you could simply add more of a suitable carrier fluid which would bring it back to it's original consistency. If this is the case then adding more ferrofluid would end up with an increasingly thick consistency over time where as adding more carrier would thin it back out or maybe even thinner than it was which means it could last much longer. I don't know that it being a bit thinner would have much effect. That or the surfactant degrades and it starts clumping.

 

[Eastwood]

I think it’s heat and time that degrades or evaporates the Statoraid fluid. One of my hub motor bikes, kind of a cruiser/mountain bike style. I put F/F around 3 years ago and it’s still good, the motor is completely sealed. the motor never gets passed barely warm. Then, with my bomber clone build, I push that motor extremely hard off road and it needs to be topped off within 12 months. That motor is 100% sealed as well so I know it’s not leaking. So I really think it’s the heat and the duration of how long the motor is hot is what evaporates the fluid. I don’t think the leftover magnetic particles is an issue. Maybe if the motors been topped off with ferrofluid 5 times or so it might be too much buildup with the magnetic particles, but not just from topping it off one extra time.

I can’t remember if you use hubsinks or not?
I’ve done it both ways with just F/F and no heat sinks and I still got cooling affect but of course with the sinks, it optimizes the statoraid.

 

[Bullfrog]

I am really torn whether to use Statorade or one of the full synthetic ultra low viscosity ATFs in my 4T Leaf 1,500w motor.

With my MAC motor, I have tried low viscosity ATF and a distilled water/Motul MoCool mixture...both worked great but the ATF leaked via capillary action through the wiring onto the rear brake disc (that got exciting when my brakes didn't work) and the water mixture would evaporate and need replenishing since my MAC ran between 100C-120C (I pushed it hard at slow speeds).

Hopefully the Statorade and ULV ATF would not leak via the wiring since the level is so low compared to what was required for my MAC...I had to use 4-5 ounces of fluid to bridge the stator to shell gap in my MAC.

I am not sure what carrier fluid is used for Statorade but I would think over time it would evaporate and possibly the surfactant as well. Continually adding new Statorade might eventually cause a lot of drag since the solids loading would increase over time if you don't open the motor and clean it. When I asked Grin Tech about the carrier fluid, all they would tell me is that I should seal my motor because the carrier fluid was slippery and it would affect my brakes if it leaked on the disc...that leads me to believe it is a petroleum product and some have speculated it is kerosene...the boiling point of kerosene is between 150 and 300 °C (300–575 °F) so hopefully my motor never gets that hot but it will still evaporate at lower temperatures.

I am trying to convince myself that ULV ATF is a good idea .

 

[fechter]

Ferrofluid comes with two types of carrier fluid. I don't remember which one is used in Statorade. I think it's an oil similar to the oil used in air conditioning compressors. It does not evaporate at normal temperatures.

 

[amberwolf]

If it's helpful, from:
https://www.delphiautoparts.com/res...l-why-quality-and-quantity-are-both-important

1. PAG oil: Polyalkylene Glycol or PAG oil is a man-made lubricant used in both R134a systems and the latest R1234yf. There are several types of PAG oil based on the viscosity of the oil -- PAG46, PAG100 and PAG150 -- and the type of refrigerant it is designed for. Unfortunately PAG is hygroscopic, meaning it attracts and retains moisture from within the A/C system or atmosphere. When PAG oil and moisture mix, they react, creating an acid that can corrode and damage system related components. For this reason, PAG oil should never be used to lubricate O-rings, compressor shaft seals or refrigerant line joints. More important, it should also never be used in hybrid vehicles as the oil is electrically conductive.
2. Mineral oil: Mineral refrigerant oil, also known as Alkyl Benzene Oil, was the default option up until HFC refrigerants became common place. Today it is still used in older R-12 refrigerant systems. And because it does not absorb moisture, it is also used to lubricate O-rings and seals in both R-12 and R134a systems.
3. POE oil: Polyolester, ester or POE oil, has also been around for some time, however, up until now it has not been recommended by many manufacturers because it does not perform well in high heat, load conditions and it absorbs moisture. The one exception is hybrid vehicles with an electrically-driven compressor. POE oil has greater insulating properties than PAG and can help to protect the insulation on the windings, preventing electrical leakage. Using the wrong oil in hybrid vehicles may allow current to short circuit back through the A/C compressor, creating a shock hazard.
4. PAO oil: Polyalphaolefin- or PAO-based oil is a multi-grade synthetic oil. Compatible with many lubricants and refrigerants, it is intended for universal application and is sometimes used as a substitute for certain PAG oils if approved by the compressor manufacturer.

 

[amberwolf]

I am really torn whether to use Statorade or one of the full synthetic ultra low viscosity ATFs in my 4T Leaf 1,500w motor.

Statorade only needs enough to gather itself between magnets and stator teeth.

Any non-magnetic fluid will need enough more to fill the side cover area around that section, and allow for splashing and coating of all areas of the motor where it will get onto and then run down when you stop, etc. I suspect it will require many times greater volume, and since it won't be held in place near the magnets, it will end up essentially everywhere in the motor. It might not be enough to be wicked out the wiring in quantity, but I suspect some of the splash that ends up on the axle will wick into the wiring even if it doesn't make it out of the motor, and some of that splash will wick out between the bearing ID and the axle if it's not an interference fit, and do whatever it does via gravity/etc once it's out.

 

[AGS]

I have an oil cooled geared hub motor and the ATF does wick out through the wiring. I have managed to seal the axle and side cover so it doesn’t leak out everywhere else.

I have been searching for some ferrofluid for my QS205, but the only stuff I can get in the UK has a low flashpoint and I don’t fancy using that in my motor.

 

[Bullfrog]

Any suggestions on the volume of Statorade I should use?

My Leaf DD Motor will be set up to run 45 mph/73 kph/600 rpm and the faster the motor turns the more you need to increase the volume of Statorade in the motor. The speed/rpm is above the highest I saw on Justin's charts. I believe the Leaf stator is ~35mm x ~205mm.

Decided against ATF due to capillary action causing leakage via the wiring...even though there are some new ATFs that are "Ultra Low Viscosity" (4.5 cst@100C). Thanks to Amberwolf for his comments that brought me back to reality.

 

[E-HP]

I placed some pics in the Leaf thread of how the motor looks inside after 8k miles.

Leaf / leafmotor / leafbike high efficiency 1500w motor

Making something more efficient to reduce the heat created in the first place would be good, though; if that's what you meant. ;) Yes, that is what I meant. (Example) If two motors are going against a headwind or up a hill at the same speed at the same load then I would expect the less...

endless-sphere.com

Still deciding on how I'm going to top off the Statorade; by either just adding a little more, or scraping out the stuff between the magnets, then reapplying it.

 

[E-HP]

The Statorade, after 8k miles, still looked like it did when I added it. The carrier fluid still flowed with no sign of gumminess. Sort of the same viscosity as ATF. The Statorade stayed put, in the narrow channel between the magnets, with the only difference being it didn't not protrude above the magnets as much as after the first application, so not bridging the gap as well. The outer part of the stator was lightly coated with the carrier fluid, so it was probably still partially working.

I reapplied Statorade exactly as before, letting the magnets pull it from the syringe, and added about 2ml, at which point it looked like after the first application..

Leaf / leafmotor / leafbike high efficiency 1500w motor

Making something more efficient to reduce the heat created in the first place would be good, though; if that's what you meant. ;) Yes, that is what I meant. (Example) If two motors are going against a headwind or up a hill at the same speed at the same load then I would expect the less...

endless-sphere.com

I rode up and down the hills today, and it was immediately apparent that the motor was back to performing as it should. It was running about 10C cooler on average than it had been lately, but the best part is how quickly it cools when off throttle or feathering it to keep watts down. The cooling is immediate and drops the first several degrees quickly when off throttle, and continues to cool even under moderate power.

I think just doing an annual inspection of the motor would be a good idea, and topping off the Statorade, if necessary, could happen at that time. That would likely be before any noticeable degradation, but it's probably better to stay ahead of it rather than fall behind, and two years is too long anyway.

Between the left over Statorade that I have is two other syringes, and this one that is mostly full, I have enough for a few more years.

 

[fechter]

Thanks for the long term report. The stuff in my A2B seemed to be still working last time I rode it, but that's been over a year now.