What is David Paule smoking? In his shop tip [“Magnet Clamps,” March 2018], he seems to be saying to use magnets on aluminum. I talked to K&J, and they tell me their N42 magnets will not work on aluminum.
—Charles W. Crossman
David Paule responds: In spite of the fact that here in Colorado, dope is legal, I don’t use the stuff. But I do know that aluminum is more or less transparent to magnetism. So here’s the secret, and I apologize for not making it clearer: Use magnets on both sides of the assembly. They attract each other. It really works.
I agree with Bob Hadley that TIG welders are best [“Home Shop Machinist,” January 2018]. But since my EAA chapter didn’t win one like Bob’s chapter, I’m hoping you can recommend an economical AC- capable TIG welder.
Bob Hadley responds: Unfortunately, there are no economically priced AC- capable TIG welders. The lowest-price name-brand machine I found was $699.99. It’s Chinese-made, but has a 3-year warranty and is imported by Eastwood, which is a pretty big outfit.
A used machine might be an option. But I am sure you know that used Miller or Lincoln TIG welders on eBay often sell for near retail.
Perhaps a welding class at a local community college might be the most economical solution to gain access to a high-quality TIG machine.
EFII System 32
As the manufacturer of the heart (ECU, programmer, crank sensor) of the “legacy system” mentioned in your EFII System 32 article [“Under New Management,” March 2018], I’d like to correct a few details and give credit where it’s due.
The SDS EM-5 ECUs used by EFII from 2011 to 2017 fit a 16-bit processor, not 8-bit. Because of our compact code, the 16-bit CPU executes the main loop in 209 millionths of a second, which is more than fast enough to track any relatively glacial changes in sensor inputs on a slow-turning Lycoming engine. This design came from motorsports where engines have quintuple the rev range and quintuple the rate of acceleration compared to Lycomings. The same processor family was used on several other well-known programmable 3D EFI systems.
SDS 2D mapping has been proven over 24 years and 9600 controllers sold, to be easy to understand and accurate (+/-1 degree of timing and better than 1% AFR). Our opinion is that 3D systems will not make a Lycoming run smoother or respond faster.
With regards to “new” features, SDS has had things like closed loop since 1995, knock control since 1996, aviation programmer since 2006, lean warning/auto enrichment since 2007, MAP averaging and full data logging since 2014, dual access programmer since 2015, individual cylinder trim, internal digital fuel flow, baro, LOP switch, and cylinder mounted injectors since 2016.
Our next generation EM-6, which will be released this year, is already evolving, building on our multiple, earlier ECU designs, and adding more capabilities.
Simple Digital Systems