F

Flying Scotsman

Well Known Member
Before I go out and a) buy a new tool, and b) watch it tear up a part, thought I'd ask...

any suggestions for cutting the 2" dia lightening holes in a -7 battery box? It's .032 steel, so I'm in a bit of a quandary over the best way to do this...knockout punch? some magical hole saw that won't tear up the part when it binds? etc...

Did a search, but couldn't find much info...all help is much appreciated!

Steve
 
Any bimetal holesaw will work just fine. Also, it doesn't need to be 2"--just use whatever (smaller) size you have around. It helps to put a piece of wood on the inside of the box to serve as a backing block. Good luck.
 
I'd just go for the cheap 2" round hole saws.

If you get into cutting large round holes such as 5,6,7,8"................I'd go with the Malco drill router than you can get at Home Depot for $59 in the heating/sheetmetal aisle. It's adjustable, and uses a drill bit that goes in your drill. Wouldn't use it for instruments though. I prefer the fly cutter.

L.Adamson -- RV6A
 
I didn't bother to cut the holes in the battery box. I probably would have if I had a 2" hole saw, but I didn't see the point in buying one just to save a few grams of weight. I know there are threads discussing the weight savings of the lightening holes, but I wonder how much weight is saved in total on the entire airplane if all the lightening holes are cut out. I'd be surprised if it was more than 2 lbs. :rolleyes:
 
cooling holes

The holes might make the battery box a bit lighter, but my guess is they're there to provide cooling for the battery.

Tony
 
Tony Spicer said:
The holes might make the battery box a bit lighter, but my guess is they're there to provide cooling for the battery.

Tony
Click to expand...

I'm pretty sure that the battery won't generate enough heat during it's charge cycle to be noticable...if anything, I would think protecting the battery from heat inside the cowl is more important. That's why many of the Odyssey batteries you can buy have a metal jacket on them...for protection from heat.

Then again, what do I know? ;)
 
I tried 2" instrument punches and fly cutters. In the end, I'd recommend no holes or using a unibit with lots of lubricant to cut a bunch of 3/4" holes.

Using a fly cutter is noisy!

Vern
 
I didn't bother to cut the holes. My O-360, fixed pitch Sensenich -7A is a little too light in the nose anyway. After 3 1/2 yrs. and 400 hours, I haven't had any battery issues with my PC-680.

Mike
 
lostpilot28 said:
I'm pretty sure that the battery won't generate enough heat during it's charge cycle to be noticable...if anything, I would think protecting the battery from heat inside the cowl is more important. That's why many of the Odyssey batteries you can buy have a metal jacket on them...for protection from heat.

Then again, what do I know? ;)
Click to expand...

Well, not exactly. The metal jacket is there to keep the plastic case from deforming should it get too hot due to a lack of holes in the battery case :)

http://www.odysseybatteries.com/odyssey101.htm#mj

Tony
 
PC680

These batteries have proven great endurance expecially with a battery tender attached in the hangar period. Extra weight... its gotta go! :D
 
Greenly Punches

My battery box was so tough I ruined my flycutter, and had no better luck with a new set of milwaukee hole saws...until I tried Greenly Hole punches:)..they did a great job..no muss, no fuss...clean and quiet..by the way, if you have these punches do not use them on stainless steel..only soft steel like the battery box...(don't ask me how I know about the stainless....:mad:)...
 
Tony Spicer said:
Well, not exactly. The metal jacket is there to keep the plastic case from deforming should it get too hot due to a lack of holes in the battery case :)

http://www.odysseybatteries.com/odyssey101.htm#mj

Tony
Click to expand...

Hi Tony,
I think you're misinterpreting the following (from the link you sent):

Metal jacketed vs. Non-metal jacketed: The metal jacket is needed if it's being mounted near heat to protect the plastic of the battery from swelling. The lead plates are under much higher pressure than a lead acid battery and if the plastic heats up, the plates will want to expand outward which can ruin the battery if it doesn't have a jacket.

Note the part about the battery being mounted "near heat"...that doesn't mean it's generating that heat inside the case. Because of the higher pressure of the lead plates inside the battery, it's more likely to deform if the plastic heats up from an external heat source. ;)
 
Thanks, everyone...another reminder of why this is a great forum! Ended up having access to a professional's (electrician's) knockout punch set...made quick work of it, and then all that was left was to clean up the holes.

(Sad to say, the punch set from HF failed pretty miserably...stripped threads :( ).

I'm going to have to get and learn to use a fly cutter, it seems...they look damned dangerous to my untrained eye, but it seems a lot of people like them...anyway, thanks again for your suggestions!

Steve
 
Corrosion

I didn't cut holes in my battery box for the simple reason that I didn't want to cut through the protective powdercoat and end up with the steel rusting.
 
To me, "building light" means seizing every opportunity to shave weight wherever possible. Naturally, steel is heavier than aluminum and I took full advantage of the plans call-out to remove the excess material using a fly cutter. I'm satisfied a little touch up paint on the hole edges will stave off corrosion in my lifetime.

 
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Lightening holes

lostpilot28 said:
I know there are threads discussing the weight savings of the lightening holes, but I wonder how much weight is saved in total on the entire airplane if all the lightening holes are cut out. I'd be surprised if it was more than 2 lbs. :rolleyes:
Click to expand...

I built an RV6 and saved separately only the cuttings made for lightening purposes in a large coffee can. After the plane was complete I had 9 pounds of actual scrap and I felt the shavings from cutting and the use of a belt sander if a person could measure it would increase the weight savings by by another couple pounds. This can did not include any cutoffs or edge trimmings for fitting parts which is really not a product of the lightening process.

FYI...Total empty weight came to 1049 pounds. RV6 slider, 3 color paint, fabric upholstery, IFR steam Gages, 0-320 with Hartzel CS prop, Garmin radios, digitrak AP with Altrak VS., complete lighting w/strobes.

Dick DeCramer
N500DD flying @ 300 hours
Northfield, MN
 
Do not use a hole saw, unless your ready to buy a half dozen of them, and almost ruin a battery box. I am very disappointed in the product Vans sells. The holes should have been cut before the box was assembled/painted.

If I had it to do over again, I'd boycott Van's battery Box (ES PC680), until they offer the box with the holes cut out. :mad::mad::mad:
 
#N72CR said:
Do not use a hole saw, unless your ready to buy a half dozen of them, and almost ruin a battery box. I am very disappointed in the product Vans sells. The holes should have been cut before the box was assembled/painted.

If I had it to do over again, I'd boycott Van's battery Box (ES PC680), until they offer the box with the holes cut out. :mad::mad::mad:
Click to expand...
Were you using a regular (wood) hole saw or a "bimetal" hole saw? If you used the latter, you shouldn't have had any trouble. Not only do they work well on the battery box, they also cut through the thin firewall nicely so long you use a backing block. I would never try either with a regular wood hole saw.
 
I may be missing something, but I used an aluminum box and cut the holes with a flycutter. I think I got the box from Spruce.
 
Sears Fly Cutter

I used the fly cutter I purchased at sears. Worked great.

IMG_8595.JPG
 
alpinelakespilot2000 said:
Were you using a regular (wood) hole saw or a "bimetal" hole saw? If you used the latter, you shouldn't have had any trouble. Not only do they work well on the battery box, they also cut through the thin firewall nicely so long you use a backing block. I would never try either with a regular wood hole saw.
Click to expand...

I was using a bi metal saw. And I used wood blocking for support.

I found another reason why the holes should not have been drilled/punched before the box was spot welded together. It appears cutting into the box puts a ridge around the inside lip of the hole...although very minor, it defeats the purpose of the steel box in protectiing the battery.

I did not have a 2 inch punch set, but it too has to cause some disformation to the battery sheet metal.

I'd bet the enclosure is made by someone else, and they would cringe at how Van's customers are hacking them up to save 3 ounces.

I'm throwing away my ES PC680 battery box, and re-ordering a new one. There is absolutly no reason to remove protective material from a battery enclosure.

As for cooling the battery, it would make more sense to install cooling fins to the enclosure, if that were an issue.

(Van's boxes are made of steel, and spot welded together)

(Just my 2 cents)
 
I used a Blumol hole saws. I paid like $50.00 for them 15 yrs ago or so. I bought them from Northern Tool. It worked like a charm. I put 2X4's inside then made sure I had the drill press on the slowest speed ( about 500 rpm), use Boelude and went to town. On a side note, I always wonder why not an aluminum box instead of steel? I thought about trying to build one for fun.
Rick Maury
RV7 SB
Tail and Wings done, Fuse. in the works.
 
Steel VS Aluminum

The whole time I was reading this thread I'm thinking why is the battery box steel? I just payed over $ 500 bucks for a new one in my spam can and it has a heavier batt.and its made of alum. Now that is exactly one of the reasons I'm building, I hate being taken for 500 bucks when I could have made that cessna box myself for 20 bucks and some time. I added the batt box to the delete from kit notes and will use the alum. one from Spruce. Gene
 
If I do it again, I would just use a Unibit to bore holes. Will look like Swiss cheese, but wouldn't ruin a fly cutter.

As it was, I used a Greenlee punch but the Unibit works well.

Vern
 
Steel for structure?

I was wondeirng why the battery box is steel also? Structural reasons? The much bigger battery box in my Skipper (that holds a much bigger and I assume heavier battery) is aluminum.

The Skipper box is a big complicated thing, with a venting system that looks like it came off a fighter jet. I assume that is because the old lead acid batteries leak / vent easily. It is my understanding that the Odyssey batterys are completely sealed and can't / won't leak or vent. Is that true?

I don't like the idea of a heavy steel box, unless I can understand why it needs to be a heavy steel box. Hopefully one of you ME's will explain it!
 
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