Tuesday, June 21, 2011

Motor Drama

I have refrained from posting about this for a variety of reasons, but mostly because I wanted to write it up in one story once I knew the whole story.  While there's no "happily ever after" quite yet, but I'm optimistic that there will be.

Sometime this last February I noticed a disturbing, but familiar feeling in the car's drive line; vibration.  It started small, and I kept telling myself it was my imagination.  But two weeks or so later, there was no denying it, the wobble that forced me to pull the motor a year ago was back.  I was, and remain absolutely perplexed as to how this happened.  I took the cooling shroud off the front and, sure enough, the balancing putty fell out the front.

I contacted George Hamstra and Netgain and told him what had happened.  He was more shocked than I was.  He explained that only one other motor had ever had the balancing putty come off, and that was because the owner had spun the motor up North of 9000 RPM.  He went on to say that they had never seen it happen twice!  Well, my motor has never seen anything over 5000 rpm, so that wasn't it.  I also have cooling air forced into it constantly, so heat shouldn't have been a factor.

George talked with the folks at Warfield electric, brainstorming on what the possible cause might be.  They were able to rule out the RPM and temperature possibility right away.  The wondered if perhaps they had a bad batch of putty, but reasoned if that were the case, then they would be seeing failures on multiple motors since a single batch will be used on several motors.  Well that wasn't happening.  They speculated that perhaps it had been applied poorly.  Who's to say, but it seems unlikely that it was applied poorly twice on the same motor.

George joked that "It's just you Tim!"  Truthfully, I don't know that he's wrong.  I explained how I had the motor mounted up in as much detail as I could.  The motor was tied down to the sub-frame of the chassis with a rubber pad under it to absorb shock as it moves down relative to the car.  He commented that what I described to him should be absolutely adequate.  In fact he's seen installs where the motor is tied directly to the chassis with no dampening material at all, so the motor feels every shock the chassis does to no ill effect.

We were all left scratching our heads.  I'm perfectly willing to accept the fact that it was something stupid that I did in the mount design or build, but I don't know what.  I'm also willing to believe that the putty just wasn't applied properly, but I have no evidence that's the case.  Presented with no clear cause to the problem, George stepped up and did what I think few manufacturers would do these days; he offered to fix it and cover the costs.  He and his crew arranged to have the motor picked up, shipped to Warfield Electric, fixed and shipped back at their expense.  I assure you this is not an inexpensive endeavor.

But then he went a full step further saying that if this doesn't fix the problem, he just wants to replace the motor.  I'm speechless really.  It's so reassuring to know that ultimately, I'm going to have a good motor.  On the other hand, I desperately don't want it to come to that.  At this point I'm certain that George has lost money on my motor, having to shipped and repaired it twice. He'd be better off never having heard of me.  This is a painful prospect to me.  The one way we have as consumers to vote for products we favor in the market and to support companies we believe in is to hand them our cash.  I don't know of too many causes, companies or products that I support more than EVs, Netgain, and the WarP motors.  So the fact that my "vote" has been nullified because of this pains me.  My hope is that this is the last time the motor is out of the car for repairs.  My hope is that the only time George hears from me again is when I tell him I'm buying another motor for another project.  Time will tell.

So, Netgain and Warfield have done their part to try and put a reliable motor in my hands.  The question now is what am I going to do?  As I mentioned before, I don't know if the way I had the motor secured to the car was the cause of my problems or not.  George may look at the car at the EV Converters Convention (EVCCON) in Missouri in September and say "Wait, you mounted it like this?!  You fool!!" and punch me in the face.  I don't believe there was a problem with the mount at this point, but I've decided there is an area where it could be improved.  Take a look at this crude drawing...

This is not too different from the old support with the exception that there is now some new rubber above the angle iron supporting the motor.  That additional rubber should offer additional cushion to the motor from movement.  In the previous mount, which does not have that upper rubber piece, if the chassis dropped down suddenly, the motor would be forced down, incurring a bit of a shock while it followed the chassis downward.  However, the new design will allow a little cushion to that shock providing some buffer to the motor when it moves both up and down.  What isn't represented there is the strap that goes around the motor to hold it down to the mount, and the bars mounted from the motor to the chassis for anti-torque support. 
Will this be sufficient to protect the motor?  I certainly hope so.  I've sent the design to George as well, looking for his input. 

At any rate, the motor arrived back from it's repairs yesterday and looks as beautiful as ever.  They even gave it a fresh coat of paint.  I'll be mounting it to the transmission over the next couple days and dropping it back in the car.  Once it's in place, I can start fabricating the new mount so it holds the motor in the right place.  I'm going to be building a whole new one from stronger materials rather than adapting the old one.  I think it will be easier to incorporate the change on a newer build. 


Anonymous said...

Hi Tim,

Sorry to hear the putty has come of again. The motor runs smoothly by itself though? No high rpm shudder?

Did you solve the 48V supply already for the AC?

kind greetings from the Netherlands,

Tim Catellier said...

Hi Steven, it's good to hear from you.

This has been a very frustrating incident. As soon as that putty came off, the whole drive line began to wobble. It's not real bad, but it's noticeable. George at Netgain had said that in the long run, it would be hard on the bearings and in extreme cases could warp the big end plates on the ends of the motor.

The vibration was most noticeable at about 3000 RPM, but you could definitely feel it at 4000.

I think I have a couple ideas for resolving the 48V supply. One is a sure thing, but not the ideal, the other is still an uncertainty, but I would prefer it.

Vicor makes a 500W 48V DC-DC converter in brick form. I'd need two of them in series and they are about $225 each. I'd use those to power the controller I'm getting with the compressor.

Option two is Masterflux makes a controller that will take my pack voltage and may power my compressor. I need to contact them to clarify. That's a $640 part, but it would be the only part needed, so I'd prefer that.

I'm simply not knowledgeable enough to build a power supply, so I'm stuck buying an off the shelf solution.

I'll keep everyone posted on the blog.