Floor pan rivet failure

[bball7754]

Discovered an interesting issue on my '98 Caterham this past weekend.

 

About 15 of the rivets holding my driver's side floor pan had failed. The rivet heads had separated from the rivet bodies, and the floor pan was sagging by as much as 1/2". Since the seat is only mounted to the floor pan, it was a bit disconcerting, particularly with a track day at Putnam coming up this weekend.

 

A quick search on Blatchat revealed this is a fairly common problem. Easy to fix - just used a 5/32" drill to get rid of the rivet bodies, then re-riveted the pan. But not something I would have thought to check.

 

Steve

[Mike Rohaley]

I had the same problem in the same place on my car which was discovered this past winter. Mine were only 4 rivets and the gap (unloaded) was only about 1/32". It developed within this last driving season since the car is given the once-over every winter.

 

One thing for you to be aware of; Caterhams use monel rivets which can easily be ordered from Caterham USA. Monel rivets are a special nickel/copper alloy which is designed for use in high corrosion enviroments (such as marine) and have a very high sheer strength. Do not just run out to the hardware store and pick basic aluminum rivets or you will be replacing them relatively soon.

[Mike Rohaley]

One tip to include. When you drill out the remains of the old rivets, spray some motorcycle chain lube into the holes. The lube is viscous when sprayed but tacks up as it drys and will keep the remains from rattling around in the tube for eternity (not to mention it provides a bit of rust protection).

[Kitcat]

Also had the identical problem in the identical area last year on my '97 Caterham, built in '98. I assumed this was atypical but it sounds like a common issue at this point.

 

I ordered Caterham spec rivets from Sevens and Elans tho used hardware store rivets short term as I wanted to be on the road quickly.

 

Mike

[MichaelD]

Ditto that. Lost about 15 rivits. All on the drivers side??? I guess 20,000 miles I will do it again.

[JohnK]

One tip to include. When you drill out the remains of the old rivets, spray some motorcycle chain lube into the holes. The lube is viscous when sprayed but tacks up as it drys and will keep the remains from rattling around in the tube for eternity (not to mention it provides a bit of rust protection).

 

Good practice. Also recommended is LPS 3. The aircraft people use it, so it must be worthwhile

[scannon]

After seeing that many cars having rivet problems, I had a look under my car this evening. The cars has a little over 7k miles on it. No missing rivet heads but I did notice that the floor under the driver seat is sagging a little. Probably due to that fat bastard that had it before me.

 

Oh, wait a minute, the previous fat bastard was me when I weighed 90 lb more than I do now.

[slngsht]

not having seen how the cats were laid out, I stayed on the safe side and put two 1" square tubes under the front and back of my seat. I suppose that explains why all the little scales run away when they see my car coming.

[slngsht]

BTW, if you can't get rivets from Cat USA, you can try Fastenal or McMaster.

[slomove]

I don't want to question the wisdom of Caterham using Monel rivets on an aluminum skin but this is inherently problematic. The electrochemical corrosion potential between Monel and aluminum is 800-900 mV (meaning the materials make for a nice battery) and this can lead to serious corrosion in wet environment, especially if salts including road grime are involved.

 

I read of people who need to use the Monel rivets for their better strength with aluminum and stainless components (aircraft or achitectural) but they typically set the rivets "wet" with appropriate sealant to preclude moisture intrusion or at least cover with zinc chromate primer.

 

On a Seven I am not sure if the rivets are really stressed that much, considering the thin aluminum skin they are holding. Maybe regular aluminum rivets would be just fine and eliminate or reduce the corrosion problem?

[TheDingo8MyBaby]

Good point Gert, though we do have a favorable anode/cathode area relationship so this may not be so big of a deal. If the driver is light enough, I would guess aluminum rivets should do the job.

 

Something better than chain lube would be something like this: http://www.bergdahl.com/ps-870.htm I've used it on aluminum structures for years without any issue.

[Mike Rohaley]

The chain lube was for the purpose of keeping the old rivet remnants captive so they would not rattle. For keeping corrosion at bay in the space frame I would suggest ACF-50 which is available from companies like Aircraft Spruce.

[lowflyer]

When checking the catalog from Aircraft Spruce, check out the "Cherry" rivets, which are structural, meaning that the mandrel stays in place after "popping".

 

Used in aircraft building, I used them in the floor of the Stalker, no problems - and I am a fat old bastard!

 

Ken Edney

Chandler, AZ

[solder_guy]

not having seen how the cats were laid out, I stayed on the safe side and put two 1" square tubes under the front and back of my seat. I suppose that explains why all the little scales run away when they see my car coming.

 

I have my leather Caterham seat bolted to two 1/2" steel bars which are bolted to the underside of the frame using grade 8 bolts .. .. no rivot problems on my 1981 Rotus ...