Lightspeed Electronic Ignition Direct Crank

AlexPeterson · #1 05-11-2006, 09:02 PM

I am almost done installing a dual Lightspeed, direct crank pickup system in my RV6A. I am running into some trouble obtaining functionality with the required gap between the sensors and the magnets. The install manual indicates that the gap should be between .030" and .060". However, when I set it at anything over .040", one of the four Hall effect sensors no longer fires. The designer, Klaus, tells me that the sensors should trip out to .100" if the magnet is over the center of the sensor.

What I'm looking for are real life experiences from those who have installed this system, specifically how large was the gap between the magnet and the sensor when it no longer would function?

Thanks -

Kahuna · #2 05-12-2006, 05:39 AM

I had real trouble getting this right. I was not getting good results using the method described in the manual for the gap. SO what I did was take 1" long pieces of masking tape, and mic them to 060. I think it was about 6 layers or so. I would put that tape over the pickup, mount the ring gear, tighted it all down with dummy bolts, and spin the engine. If there were markings on the tape from rubbing, Id add a washer to the PCB mount to increase the gap.

I originally had 030 gap (using the tape method), and after about 3 hours of running I had scuffed the pick ups of the board enough to cause them to fail. WHich meant sending the board off for repair. Meaning, 030 was not enough gap for all the play required. for the pressures of jerking a c/s prop at 160kts to idle, going fine pitch, and having the back load push the prop against the PCB pickup.

I never tried to see how much gap I needed to make the p/u fail. But my guess is that you are not getting an accurate measurement using his gap method. The only way to really know what the gap truely is is to mount the gear with the tape on there to get it to scuff the tape. Also anoth real issue is that the PCB mounted has different gaps at different locations around the circumfrence. So bu using the tape, you know exactly what the gap is as the gear passes by each pick up.

Hope this was clear.

Best,

AlexPeterson · #3 05-12-2006, 06:11 PM

Kahuna,

Thanks, I like that idea. Last night I was at the hangar for a bit, and thought that putting a little bit of clay on the sensor would be a good plan to accomplish the same thing. I didn't have clay, but I had some duct seal. Here is what I did: I aligned the crank so that the magnets were right over the sensor, removed the flywheel, put a little piece of the duct seal on the sensor, and then carefully mounted the flywheel, being careful not to let it tilt towards the sensor. This method also allows for examining the exact radial alignment also. However, the duct seal is a little to soft and sticky, so I'll bring a little clay out next time.

The ruler method shown in the instructions is a joke. I used a dial caliper and sound metrology methods to determine the gap.

Also, I was told to skive off the sealant which crowns the sensors, that should give me some more margin.

Kahuna · #4 05-13-2006, 05:26 AM

Your on the right track.
Your goal is to determine what the gap is with the flywheel on.
You'll get it now.
I would use ~045 as my gap. Remember, 030 caused me to scuff the sensors to repair.

Press on
Best

AlexPeterson · #5 05-14-2006, 06:58 AM

Problem solved. Several things were conspiring to reduce my margin. First, I discovered that one needs to take a razor blade and skive off the sealant covering the four sensors (direct crank pickup). This sealant was about .025" thick. I do not know why they don't remove the sealant at the factory. Second, the assembly ended being about .015" off center with respect to the crankshaft. I do not know how this happened, as there are break away tabs on the assembly which remained in place until after mounting. I biased the circuit board towards the center when I mounted it to compensate for a bit of this.

As written earlier, the method I used to nail what the clearances are was simply clay. I put a little blob over the sensors, and carefully put the flywheel on with a couple bolts. I then removed the flywheel, taking care not to rock it towards the side of interest. Using a razor blade, I scraped half of the clay off the sensors, and used a dial caliper to measure the gap.

I ended up with about .035" clearance (crank pushed aft), and, importantly, I verified that it would function with an additional .025" temporarily added with washers and another .010" added by pulling the crank forward.

I feel strongly that finding the point (the gap, that is) where it doesn't function any longer is important. Simply setting the gap at the target .030" to .060" doesn't tell you if you are close to the edge of non-functioning or not. I want to know if, as things drift over time/temp/whatever, that it will continue to function.

osxuser · #6 05-14-2006, 09:54 AM

A little off topic perhaps, but what is the advantage of using this setup over a sensor in the mag drive?

DickDe · #7 05-14-2006, 10:13 AM

I also am interested in the difference between the replacement module for the Mag. verses the crank sensor mounted near the prop flange. I currantly have conventional mags but considering a change one Lightspeed.

Dick DeCramer
N500DD RV6
120+ hours
"Keep riveting 'cuz after each hour they seem to fly better!!!"

dan · #8 05-14-2006, 10:52 AM

Quote:

Originally Posted by osxuser

A little off topic perhaps, but what is the advantage of using this setup over a sensor in the mag drive?

No moving parts. Lighter.

avpro56 · #9 05-14-2006, 07:49 PM

Alex:

I have just installed the Lightspeed Plasma III system in my RV-8. I'm installing a new panel and performing the fuel tank pickup modification at the same time, so it will be a while before I run the engine.

I had the same concern as you did, trying my best to come up with the optimum gap between the ring gear and sensor plate. I found the gap way too large with the stock spacers that mount the circuit board. I removed them and took about .080 off all spacers making them .232 long when cut down.

I was rvery careful making a tool to check the respective gaps, but like you I elected to use clay. It is difficult to meassure the clay becuse it is soft. I found it best to put a small amount of clay next to the sensor, then install the ring gear. It's then realtively easy to see the difference in height next to the sensor, but if you touch the clay it will spread out and distort the results.

To be sure, the gap at the bottom and top sensor may be slightly different. This may require a bit of shimming to get things right. I'll report back when I have it running.

Jon Ross
N207RV

avpro56 · #10 05-14-2006, 08:02 PM

Stephen

Quote:

Originally Posted by osxuser

A little off topic perhaps, but what is the advantage of using this setup over a sensor in the mag drive?

The direct fired crank sensor is much more precise than using the mag drive. Gear lash will make timing bounce around as much as 5 degrees, which is why many new cars have ignition crank triggers. It's all in the quest for efficiency.

As Dan points out, removal of the magento saves weight, even if you elect to use a hall effect sensor in the mag hole. It has been suggested that the magneto will take up HP becasue of the power required to drive the magneto (or hall effect sensor). Not sure now much, but I've heard it said that a vacuum pump can take 2 HP of mechanical energy to run at cruise. Maybe that's wishful thinking, but it has to take more power to run a magneto than a vacuum pump.

It's getting kind of lonely on the back of my engine without a vacuum pump and only one magneto.

Jon Ross
N207RV