Wednesday, March 29, 2017

Inspection #1

Since some help was available, I decided to get a jump on the inspection process and start on car 36 today.  Greg Ceurvorst was willing and able to help, and that made a huge difference.  It's greatly appreciated, you may be sure.

I was too busy to take many pictures, although we've published several pictures of the inspection process before.  But Greg had his smart phone along, and provided several good ones.

The 36 at the door of the barn, before being brought out for its trip to the pit:

 The motor truck over the pit:

Looking west along the track towards the 300:

I can pretend I'm enjoying this, if I don't have to keep it up for very long.

And looking out the door along the pit lead.  In the distance is our blue flag.

The inspection process went well, and there were no major problems that couldn't be fixed.  The feed valve was stuck open, but as usual a little disassembly and cleaning corrected that.  One thing that I had not seen before was that we found a contactor that had welded itself shut:

Just touching the tips with a screwdriver was enough to free them, although of course that's not much help when the car is running.  I have several replacement tips on hand, so it didn't take long to replace them.   But this is something we should keep an eye on.  Fortunately, it doesn't take long to open the box and check all the contactors if there's any question.  I might point out that having one contactor welded closed is generally not a serious problem, as long as it's discovered in time; you would have to have at least three closed to get to the point where you cannot shut off power, other than by pulling the pole.  

Although I didn't take any pictures of the car itself, I did get a snap of Greg's nifty truck:

And as usual on a Wednesday, there were lots of people working on their various projects, but as I mentioned I didn't get much of a chance to photograph them.  Later, while talking to Norm and Jeff about the contactor problem, they proudly showed me the progress being made on the front end of the 28, with the help of the welders from Belvidere:

There are a few things to finish up on the 36's inspection, all of which are easily done in Barn 8.  And I will repeat that we can always use more help on inspections.  It's always good to have another pair or two of eyes to look for possible issues. 


Anonymous said...

Nice Dodge! Could the contacts have welded themselves because a line switch did not open fast enough when shutting off? Just a thought...

I am always glad to see progress on the Michigan interurban.

Randall Hicks said...

There is no line switch in this system, only a set of 13 identical contactors. When power is shut off, they should all open at the same rate, but if for some reason they don't, I suppose the one that opens fastest will draw more of an arc. I'm also wondering if a magnetic blowout coil might be shorted. What would be a good way to test that?

sd45elect2000 said...

Watch the arc, you should hear a nice loud pop and a short flash. If it sizzles you need to change the arc chute of clean the arc chute contacts.

Randy Stahl

Colin said...

Hi Randall.

Your question about the shorted blowout coil is an interesting one. I would imagine the resistance of the coil is very low so it may be difficult to measure the difference if some turns are shorted. It may be possible to use a magnetic sensor such as a compass when the contactor is carrying current and comparing it to the other contactors. Another thought I had was about cleaning tips very often and perhaps reviewing the period between tip cleaning. From experience of diesel loco starting contactors the tips can indeed weld if the copper blobs are allowed to build up. It could just be a maintenance issue. If the blow out coil was not working perhaps also the easiest way to see this would be to compare the behaviour of the arc with a contactor that is known to be serviceable. If the coil is U/S the arc will remain stationary, whilst with a good coil the arc will be "stretched" until it is too long to sustain it's self. If the coil is U/S I would imagine a rather burnt contactor as well as the blobby tips. Hope this makes some sense.

Best wishes from England. I would say Europe, but that may be troublesome over here.

Colin Beckwith

Randall Hicks said...

Thanks for the comments. I'm reluctant to try testing this system when actually pulling significant current through the contacts, and in fact it would be nice to avoid 600V altogether. It occurred to me that we could use an arc welder as a constant-current source, to run a known current through the blowout coil without energizing the control circuits. Then ideally I would want a Hall probe to measure the field between the tips. But since I'm no longer teaching there's no opportunity to borrow the equipment I need under cover of darkness. A compass or other device might give a general indication, but I would prefer something more quantitative.

But as a practical matter I think we'll just have to monitor the condition of the tips more closely. It's not that hard to open the boxes once in a while, and at least I have a better idea of what to look for.