Here are the fets temporarily mounted to the heatsinks. I say temporarily because I forgot to add some thermal grease under each fet. But I’m glad to know that my dimensions were ok, and that everything fit nicely. I used double sided foam tape on the bottoms of the 3 heatsinks. This will isolate it from the board per Fritz, and mechanically secure it to the board.

Looks just like the picture! Shot w/G1.

Here is a closeup of the mounted fets. The screw heads just barely clear between heatsinks. So make sure when you drill and tap that you center the holes vertically along the slot. Using button head screws would give more clearance. My flat washers were a bit thick as well. Shot w/G1.

Turns out that 6-32 screws fit the fets nicely so that’s what I tapped the heatsinks with, instead of 4-40. The cnc code did fine. I had to add a step that chamfered the top of each hole so that the tap would start easier. The nicest part of using the mill is for power tapping. It makes perfect threads and the mill does the work. The 6-32 tap is the smallest I’ve every power tapped with. It’s a cheap tap too, but it worked just fine!

Here they are just finished. Image shot with my G1 cellphone.

This morning I measured out the fet placement on the heat sinks, then wrote the g-code to do it on the cnc. I debugged the g-code on the cnc too. Now I can drill and tap all 18 holes in 3 heat sinks with ease. They will all be tapped for 4-40. 3mm would work too. I suppose I could drill a clearance hole and use nuts on the back side too.

Today I just announced the opening of the US Electricar store to the US Electricar Yahoo group.

I just got the huge 4 farad cap in the mail. Yesterday I found a nice Tektronics chassis at Halted that use to be some old test instrument. If it will hold all of the larger spot welder assemblies, then it will fit on my bench very nicely as it’s narrow. The chassis was designed to sit on either of two sides. I just need to start the assembly process.

If you have not noticed or heard, I’ve opened the US Electricar.net store for USE owners so they can get repairs and parts to keep their vehicles running. There are links on this blog to take you there. Enjoy!

The 10 tooth L series pulley and belt arrived from McMaster today. The pulley had to be bored out from 3/8″ ID to 5/8″ ID to fit the Z axis motor. Now the motor has much more torque against the quill. I turned up the speed a bit and it still moves very quickly even though the ratio is much steeper. It also helps the Z axis gain some more accuracy.

Today I finally got a fixture together to wind the T1 transformers that fail on the Dolphin chargers. I used an IR led pair tied to a counter to tell me how many windings were made. I wrote several types of G-code to have the cnc mill help in the winding of these parts. It worked out well in the end after several iterations. I settled in the 532-540 ohm range after they were wound. This was a few turns under 3k. I have one more transformer to wind. I’ll take some better video with a better source. It took days to figure all of this out and get it built and tested. The original estimate for rewinding was 15 hours. By working on the G-code and the cnc hardware I knocked is down to just over 2 hours. But last night I had a better idea. Now the full rewind takes 5 minutes while the hardware counts every turn. Sweet!

The brightness of this IR led was too high. The Rx led did not like so much light. These pics were taken with my G1 cell phone since the human eye cannot see Infra-red light. Thanks to Bob at Halted for that great tip! Video camera with night shooting have the same capability of seeing IR.

This brightness worked well. I might even be able to drop it a bit more, but for now it worked fine.

Here is a winding video from my G1 cell phone. You need Quicktime to play it. I didn’t sit still long enough to show that the transformer is moving up and down via the cnc. It spaces the windings out very nicely. I borrowed the counter from my automated battery load tester.

The new quill cover for the Bridgeport that I got from Don is now installed. I oiled it up nicely and the quill moves well up and down it’s full range of motion now.

It occurred to me today that I could design a dropin replacement for the Dolphin’s filter caps, HV buss, and IGBT hardware under the main board. It would be put together a lot like the ACP cars. Separate igbt’s in parallel for each phase. Several filter caps too. This would make getting parts far easier. There is a a lot of volume to work with under the main board. I’ll have to draw it up in cad sometime to see how it will physically fit. I should dig up the ACP pics I have as well of their hardware.

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