Got Lucky - Right Place at the Right Time

[get-lit]

Now there's an ah-ha moment for me... I didn't realize the lens aperture was larger than the parabolic reflector aperture. I'd still like to see how it compares long distance with and without the lens.

 

[BVH]

1" parabolic vrs 4" lens. Sorry it was not clear.

 

[get-lit]

That's a huge difference. No reason to bother with more beamshots to figure this out. This is a method I'd never seen before in a searchlight, and I've researched all of them, so I thought. The Megaray is definitely something to be proud to have in your arsenal.

 

[BVH]

............... The Megaray is definitely something to be proud to have in your arsenal.

I am but......I always want MORE! I'm really focused on getting the 500 Watt+ Short ARC Light Cannon working. I've wanted the 500 Watt Spectrolab Starburst for ages and this will be my chance, and in a smaller package that really is handheld'able

 

[BVH]

I confirmed that the bulb in my Megaray is the Parabolic Cermax PE175BF. I did this by removing the lens holding band on the front of the bulb, carefully cutting the bead of silicone sealant holding the yellow silicone donut to the Cermax bulb ceramic body, then rolling the donut off the bulb. Lastly, carefully, by hand/finger, removing all the silicone sealant residue off the ceramic body, ensuring every tiny bit was off. Removing the band allowed me to see the part number on the bulb. According to the mfg, the donut is there to prevent flashover during starting. This is because the lens holding band was manufactured too wide and when installed correctly, it effectively narrows the gap between Cathode and Anode because it slides on beyond the Cathode lamp terminal band. When I reinstalled the lens holding band, I moved it forward (towards the front of the light) by about 1/32" from where it was. According to the mfg, this will not significantly affect the optics performance. I started the light and was able to verify that there is no flashover occurring after 10 starts, cold and hot. I have not re-assembled the light yet because I want to do some more focusing investigating so I'll have to wait to see if the magic smoking issue is fixed by removing the silicone donut and sealant. See post 120 and this will make better sense when looking at the pic.

 

[get-lit]

Be sure to run the lamp for at least 15 minutes between starts to reform the electrodes from the ignitions, otherwise the lamp won't last.

 

[BVH]

The instructions that came with the lamp advised to run it the first time for between 1 and 2 hours but didn't say anything further about minimum run times. Something to the effect that this establishes the point on the Cathode from which the arc will form in future runs to minimize future flicker (movement of the arc to different points on the Cathode)

 

[get-lit]

It's always cautioned to run for longer in the manuals for larger lamps (Strong and Spectrolab user manuals), but maybe it's because they have much higher ignition voltages for igniting larger gaps, which in turn may deform the electrodes more with each ignition. A bit OT, but my mishap with 50kv a while back put a nice dent in the nickel reflector it arced against and vaporized a thin temp probe lead. Literally turned the entire lead to gas in a single pop.

 

[BVH]

Yes, It's scary sometimes working with 10's of KV! No matter how careful I am, I still make mistakes. Just the other day, I plugged the input cables of my FMC PL8 battery charger in reverse polarity. As plain a mistake as one can make. Thank goodness that charger was programmed with many, many safety algorithms and all it does is beep at me when something like this happens. But it just reinforces the fact that no matter how careful a person is, mistakes will be made.

 

[get-lit]

There's definitely a lot of anxiety when setting up to run a test. I usually set everything up carefully and then do something else for a few hours and then come back to recheck before powering up.

 

[BVH]

That's a great practice. Definitely worth a try.

 

[BVH]

Got the MR rigged up tonight so that I could, with precision, test the beam maximum focus by shooting the Manufacturer's mechanically stopped focus, +1/16, +1/8", +3/16", +1/4", + 5/16" forward movement of the tube & lens. Now a couple of qualifiers. All shots are at F3.5 and 8 Sec. When cropping, I tried to be as close to the same for all but as you can see, I was not equal on all of them. I don't think that makes a significant difference. What I actually saw, was more dramatic than depicted. The moment I moved forward from MFG stop, it was apparent that the donut hole was developing. It is difficult to see the difference between mfg's stop and 1/16" but look closely at the size of the hotspot btw the two. The mfg's stop is smaller.

MFG's max

+1/16" forward

+1/8" forward

+3/16" forward

+1/4" forward

+5/16" Forward

MFG's max (again)

 

[FRITZHID]

well.... MB has that lens that compensates for the doughnut hole... maybe that could be used? JAT.:thinking:

 

[BVH]

Without having a collimating filter for my MB, I don't know the results of using it but what I don't understand is....You buy a MB for it's laser thin beam. If you want to flood it out a bit, use the de-focus feature. But you can do that to the point of having a donut hole. But now you can get rid of the donut hole with a filter. But why not just re-focus the beam instead of having to carry and use a filter?

 

[BVH]

Hurray! No more Magic Smoke escaping after a 20 minute run. I suspect it was the silicone sealant holding the silicone doughnut in-place and not the silicone doughnut itself. Actually, the sealant was probably to increase the amount of flash-over protection insulation beyond the doughnut because the doughnut is very thin at its' point of contact on the bulb versus its' nominal thickness of about 1/4".

 

[FRITZHID]

Without having a collimating filter for my MB, I don't know the results of using it but what I don't understand is....You buy a MB for it's laser thin beam. If you want to flood it out a bit, use the de-focus feature. But you can do that to the point of having a donut hole. But now you can get rid of the donut hole with a filter. But why not just re-focus the beam instead of having to carry and use a filter?

well, MY guess would be able to have a larger spot w/out the donut.:thinking:

 

[BVH]

I didn't mention that a while back, I was in the process of removing the front lens by removing the retention clip and then I set the light down to get a different grip. The lens fell forward striking another magnifying glass lens I had sitting on the bench and a small chip appeared. Big enough to be visible in the beam. No, it couldn't land on the carpeted bench top, it had to find the other piece of glass! I communicated with Leon at MR and asked how I go about buying a replacement. He came back saying that he would look around back in the shop to see if there was a used one sitting around. Same day he came back and said he had found one with a tiny chip on the edge that is covered by the retaining ring. He sent it to me for nothing, including postage!! And when it got here, I was extremely please to find it was AR coated! How about that for customer service!!

 

[BVH]

Maybe the only On-Board Power Megaray in existence?

26.4V/4.2AH LiFeP04 pack
Self machined Aluminum mounts and end caps
Carbon Fiber Tube

On Board battery negates need for Red Buret!

MR draws about 8.5 to 9 Amps at 26V so I expect to get maybe 20 - 25 minutes of run time.

Back end power entry end cap

Back end cap and rear battery support ring

Back end support ring flat mounting surface and screw

Front end cap

Finished

 

[ICUDoc]

That looks really nice, BVH. Lovely combination of materials. That lathe is a handy thing!!
Thanks God you could lose the beret (quite fetching, though, on the right person....)
What about a belt mount??

 

[ShortArc]

Nice work Bob!
But it's round...how can you set it down
PS. Got the 125W version, now to find the time to compare it to the 175W one.