Need Cherrymax Advice

Stalldog · #1 03-12-2012, 07:05 PM

I've been trying to rivet the dreaded HS404 and 405 to the front spar. I've been able to get six of the eight rivets in after a LOT of effort and drilling out bad rivets, but two of the holes are slightly enlarged now and I either need to get larger diameter rivets or go with Cherrymax rivets. I hate to go with larger diameter rivets and try banging them since I've had so much trouble with the AN470AD4's. I can't imagine using a stiffer rivet will be any easier. So, figure I need to consider using Cherrymax.

I have no idea what size to get or what tool(s) I would need, so any advice would be much appreciated. The rivets being replaced are AN470AD4-4 and AN470AD4-5, but the holes are now enlarged slightly so that AN470AD5's would probably be what's needed now. Need the Cherrymax equivalents.

I've looked at ATS webpage and I see different nosepieces, pulling heads, a grip gauge, and several different sizes of rivets, and I have no clue where to start.

I have a pop rivet gun that came with my Isham tool set, but I've yet to use it, so don't know if I need a different head for it or if it will work as is.

Any advice or points to references would be greatly appreciated.

GAHco · #2 03-12-2012, 07:19 PM

http://www.gen-aircraft-hardware.com...pdf/cherry.pdf

The -4 diameters can be pulled very succesfully with a hand pull Marson tool or equivalent.

Be aware for each nominal diameter there is an oversize for it.

Study the tables the grip lengths are specific based on the amount of material you are trying to rivet.

We do have small packages at a higher price per peice so you do not have to buy a 100 pcs.

Stalldog · #3 03-12-2012, 07:33 PM

Thanks, Tom. A few other questions:

1. You said I can probably use the pop rivet gun I have. No other special tooling required? Essentially just pull it like a norma blind rivet?

2. Should I consider going with the -4 oversize rivet, or just drilling out to a -5? If I do this, do you think my rivet gun will still pull it?

3. I've been reading some of the manuals on the Cherrymax site, which is similar to the link you've provided. What material rivet would we typically use on RV's? I see different materials with different alloys and shear strength's. Not building a 747 here, so assume I'd be using 5056 Al sleeve with alloy steel stem?

I'll check out your site, too, to see what your assorted packages look like -- may answer some of my questions.

Stalldog · #4 03-12-2012, 09:36 PM

Ever have something just bug the heck out of you? Okay, think I've changed my mind. Gonna buy some 5/32 rivets and try this again. Guess if all else fails and I end up with an even bigger hole I can always go the Cherymax route or just use a nut and bolt!

Wayne Gillispie · #5 03-12-2012, 09:48 PM

I ordered 5 ea of various sizes in the beginning along with a gage. My pneumatic pop riveter from avery has pulled 3/16" cherrymax rivets set at 90 psi. I have pulled many -4's with manual puller. I found if the riveting operation looks risky...throw a cherrymax in there and be done with it. It won't add as much weight as a heavy leather interior.

#6 03-12-2012, 10:06 PM

If you do go the cherry route I would suggest you get a cherry gauge also. Also if you buy just a few take note that cherrys have a shelf life, once the bag is opened the shelf life is a matter of months if I recall correctly. I don't think you can get the bags in less than quantities of 25.
One thing to consider also is that they are easy to install but can be a bear to remove.
The diameter of the hole is critical for installation as well as length.

rockwoodrv9 · #7 03-12-2012, 10:16 PM

I don't even know what a cherry max is other than some sort of rivet you can pull that will replace one you can't drive, but if there is a shelf life with them in a bag, what about when they are in the plane? Im sure they wouldn't sell them if they didn't work, so how can they be ok installed, but not in a bag? Is there glue involved? I looked at the website and still couldn't figure them out. The one thing I did notice was they are very expensive!

Why are they better than the pulled rivets used on the 12 or on the elevators on my 9? The plans call for flush 3-3.5's on the top of the skin-spar, but say the pulled rivets are ok for the bottom. If they are strong enough for the bottom, why not the top?

I know these will sound like stupid questions to most of you, but I have tried and having a hard time with the engineering not being logical to me. I guess 40 years of driving nails rather than rivets has warped my mind.

thanks, rockwood (that actually is my real name!)

#8 03-12-2012, 10:25 PM

The shelf life is for the lubrication that is needed during installation. There are many types of cherry max, some structural, some not. I would think you would want to use CR3243 (universal head, nominal diameter). Check Aircraft Spruce rivets section. Yes they are expensive. So are hi-loks, which you may consider. Hi-loks are a close tolerance bolt that come in nominal, oversize and double oversize. I wouldn't install a hi-lok without using a reamer to get the correct hole size.

rockwoodrv9 · #9 03-12-2012, 10:30 PM

I know it isn't my thread, but thanks for the info. I figured it had to be something simple like that, but was sure baffeling me how a rivet could have a shelf life. I imagine when they are necessary, the cost isn't as critical as making it work.

As for the pulled rivets in the kit - are they the same strength? Looking at both sides of the rivets in the elevator, they look pretty stout and enough of a buldge to hold pretty good. It was sure easier to pull the bottom of the elevator than squeeze my hand and the tungston bar into the spar for the top rivets.

#10 03-12-2012, 10:35 PM

I don't know what they are in the elevator, but I doubt they are as strong as a CR32xx cherry.
If you ever get a chance to look into a engine inlet duct on a CF-6, CFM-56, JT-8 or other large turbine engine you'll see plenty of them. They are that good that they can use them there without fear of being sucked into the engine.