Rivets...

[-pru-]

I'm in the process of installing a new DB-1 floor pan and have a question regarding rivet choice. The general consensus seem to be a 5/32" diameter counter-sunk head. Choice of steel vs. aluminum mandrel is in question (leaning toward aluminum) as well as grip length (no mention in all the threads I have searched). Another item I have to consider; current chassis holes are 1/8" (original?).

Checking my spares, I have roughly 150 1/8" diameter, 1/8" grip, all aluminum, pan head, Cherry-Q rivets. For grins, I trial fitted my new pan using a few of these 1/8"x1/8" rivets to find that these will easily hold the pan in place (while the bond dries right?).

I'm now faced with the question as what type of rivet to order/use. That is, do I order another 50 1/8"x1/8" to match my current inventory or the 5/32" diameter, 1/4" grip, steel mandrel, counter sunk, Cherry-Q (and drill out to 5/32 the 180+ chassis holes!)?

By the way, here's a great source for the rivets in question: http://www.rivetsinstock.com/
Great cross reference from the same site: http://www.rivetsinstock.com/rivet31.htm

[TimW]

Cherry Max 0.126 dia rivits, grip length based on the floor & tube thickness. Expensive but they do not disappear when running the car low & over curbs (and through the occasional woods). If your front and rear skids are in place, there is not a real need to have countersunk heads with the Cherry Max rivets.

Tim

[Peter Horvath]

Carroll Smith has a lot to say about aluminum v. steel rivets, but after reading all his material I use aluminum.
I would not drill the holes any larger than they already are, unless there is a good reason.
Riveting into my Van Diemen chassis has been less than satisfying, because it's obviously not solid steel but rather square tubing. Rivets like to be in a solid blind hole so that they hold firm when they pop. I think Carroll Smith uses the term "upset".
When riveting into sheet steel or tubing, the trick is to have material fully in contact with the rivet. With square tubing, you can't get inside the tube to make sure the rivet is in full contact, to get it to set firm. So I always have a nagging doubt about that.

[Bob Coury]

The last time I did this was in a 32F-I used steel rivets for strength reasons. Maybe it was overkill on my part-but back then we did not bond the pans either.

If you happen to choose Cherry-Lock rivets beware-you cannot use any rivet gun. You must use a G-30 Cherry riveter.

[RussMcB]

I did this job recently (isn't it interesting how many responses start like that? :-).

The first thing I would do is to see how well .126" cherry rivets fit in your existing holes. The reason is, you don't want to go bigger if not needed. In my case, I had existing 5/32" holes, but many were not tight enough to re-use.

While searching on ebay, I discovered oversize (repair?) rivet sizes. I bought some that were bigger than 5/32", but not as big as 3/16"

After you check holes for tightness, you should have a good list of the rivet diameters and quantities you need.

Regarding grip length, (as mentioned above), add together the thicknesses of the materials. If, like me, you have a few rivet holes where the frames tubes have been slightly "dented in", you may want/need a longer grip length for those particular holes.

My final tally was a mixture of 5/32 nominal, 5/32 oversize & 3/16, in grip lengths of -2, -3 & -4.

I had a little bit of trouble finding the exact size drill bit needed. Fractional bits weren't close enough, so I used sizes in the neighborhood of 10 through 20 (I forget which). A good conversion chart showing rivet diameters and drill bits in wire sizes should help.

Clecos are very handy in the early stages. I did not use them during the bonding phase, just because I didn't want to clean them later. Instead, after spreading hysol, I inserted all 190+ rivets, snugged them all from the middle outwards before making a second pass to actually pop them.

I used alum rivets with steel mandrels.

If you use countersunk rivets, try to obtain the nice-to-use adjustable "stops". They take the guess work out of depth and help get the heads perfectly flush with the floor pan.

The Hysol bond seemed to work great.

I liked (and used) someone's suggestion to drill "rain drain" holes in footwells, etc.

[RobLav]

I'll be doing this too in the next couple weeks on my new Citation. It seems that the new Scrotch-Weld might be better than Hysol. And use Alodine on the aluminum before bonding (or anodize it).

I also picked up a ton of CherryMax rivets on surplus - 5/32". These are stronger than the solid type. And I'm also going to weld sheet steel to the bottom inside edges of the bottom frame rails to increase the bonding surface area (like Tom Johnson recommended.)

[kea]

Pru,
Aluminum pan and steel frame, buy aluminum/steel nail Avex rivets.
Keith

[-pru-]

All,

Thanks for the feedback! Will stay with 1/8" pan head, but will switch to steel mandrel. Still need to determine grip…Anyone know the wall thickness of the DB-1 chassis bottom square tubing?

[RussMcB]

Not a direct answer to your question, but may spark ideas.

FormulaSuper had some nice aircraft tools on hand, including a tool specifically for measuring the grip length needed. It had a small, 90 degree hook. It went through the hole (of both materials), hooked on the far side and you simply ready the measurement (-2, -3 or whatever). You may be able to rig something similar. Make a very small L shaped tool, stick it in the hole, mark the depth and then measure it.

[-pru-]

Not a direct answer to your question, but may spark ideas.

FormulaSuper had some nice aircraft tools on hand, including a tool specifically for measuring the grip length needed. It had a small, 90 degree hook. It went through the hole (of both materials), hooked on the far side and you simply ready the measurement (-2, -3 or whatever). You may be able to rig something similar. Make a very small L shaped tool, stick it in the hole, mark the depth and then measure it.

Thanks for the suggestion. Actually did just this yesterday. Made my own "depth gauge" bending a paper clip into a "L" shape. Measurement with the 0.063" pan came out to ~0.153" yielding a 0.090" wall thickness. Seemed high to me especially given how well the 0.125" grip rivet is holding the pan in place, but based on the is measurement I will go with a 1/4" grip rivet. Just curious if anyone knew for certain the wall thickness...