Replacing captive nuts for frame//body bolts.

[Ashyukun]

In the process of separating the body from the frame on 16655 to be able to repair the frame rust damage, two of the frame-body bolts were seized up in the nuts and ended up spinning so the bolts had to be cut to remove the body. In addition, one of the cross brace bolts was broken off before I ever got the car. So all of those nuts will need to be replaced- I can see that the replacement captive nut is available (part #105615), but I really doubt being able to get the old one out and put a new one in and bend the metal back into place and have it not just end up spinning again. It looks like the captive nut assemblies were welded on to the frame- does anyone know if the whole assembly is available such that the old one could be cut off and a new welded on? Or something equivalent that would work (it sounds like something McMaster would carry)? Thanks!

[Rich]

The short answer to finding any DMC-specific cages off the shelf is no, there probably are none of those. And there probably never were since the cages look like they were fabricated by the supplier just for this application.

The best solution may be duplication of the damaged cages. Take the frame to a steel fab shop that can cut off the bad cages, custom-fabricate each of the cages you need and weld them on. When done you'll just drop in the new nuts. This approach fits with the frame rust repairs or restoration you might be planning anyway?

PS, McMaster does sell weld-on caged nuts, but not with any metric size/profile you need to match up with the special tapered-tip M10 body bolts and probably not with the large amount of nut position tolerance the custom frame cages have in them.

[David T]

Like Rich says, any good fabricator can make up what you need. Do NOT weld the nuts to the frame, the nuts need to be able to move a little to accommodate slight variances in the body dimensions. The cages allow for that. In the process of repairing the rust damage, fixing the cages is a relatively minor repair. The frame is made up of pieces of 16 GA CRS sheet metal with an epoxy coating for rust prevention. Before remounting the body run a tap into all of the threaded holes to make sure all of the threads are in good shape and to clear out any paint (if you are painting the frame). Use Never-Seize or equivalent on the threads. Some owners remove the epoxy paint (a difficult process!) and then have the frame galvanized (dipped in molten zinc). If you do have the frame dipped you MUST retap and drill out all of the holes to remove the zinc.

[Ashyukun]

Like Rich says, any good fabricator can make up what you need. Do NOT weld the nuts to the frame, the nuts need to be able to move a little to accommodate slight variances in the body dimensions. The cages allow for that. In the process of repairing the rust damage, fixing the cages is a relatively minor repair. The frame is made up of pieces of 16 GA CRS sheet metal with an epoxy coating for rust prevention. Before remounting the body run a tap into all of the threaded holes to make sure all of the threads are in good shape and to clear out any paint (if you are painting the frame). Use Never-Seize or equivalent on the threads. Some owners remove the epoxy paint (a difficult process!) and then have the frame galvanized (dipped in molten zinc). If you do have the frame dipped you MUST retap and drill out all of the holes to remove the zinc.

Actually from the look of it, I can probably fabricate the cages to hold the nuts myself without too much difficulty- so it sounds like that will be the way to go. I will definitely be putting plenty of anti-sieze on the bolts before I install them.

I'm actually going to be sending the frame off to be media blasted to remove the original epoxy coating and surface rust later this week as it badly needs it (see picture). The same place quoted me a surprisingly low price ($350) for powder-coating the frame once I'm done with the repairs and any modifications, but I'm not certain that I want to go that route. Having the frame galvanized was something I considered, but I've heard warnings that the hot zinc dip can cause frames to warp. Is that not generally a problem with our frames?

Front Frame.jpg

[David T]

Warpage is a consideration but if the metal is not too thin from rust and the shop preheats the frame and knows what they are doing it should not warp. It WILL add weight but it will last forever! Powder coating is the next best thing but not as good as a proper zinc coating. Dipping in molten zinc will burn off any epoxy left on the frame including all of the "hidden" areas that you can't do with painting or powder coating and coat them with zinc. Not many shops have a tank big enough and some shops charge a fortune to do it but galvanizing is the way to go! Just get all of your repairs done and when you get the frame back drill and tap all of the holes. FYI, all of the later model Lotus's have zinc coated frames. The epoxy was OK but after a lot of years the epoxy gets hard and brittle and when the frame flexes it cracks the epoxy allowing moisture to get to the bare metal. The zinc coating is sacrificial and "self-healing" and provides longer and better protection. If you want the frame to look "original", you can always paint the zinc coating grey.

[r00b]

If your frame does warp, it will straighten out when you have all the weight of the car back on it.

[82DMC12]

Trying to understand what it is you need here. All of those nuts (105615) can be removed from the cages without damage (they just slip into the cage) and they can be replaced. I did it on my own car while doing a frame-off. Got a picture of what exactly it is you are asking about? None of the nuts require bending metal to get in and out.

If you are worried about them seizing up in the future, just replace the square nuts, get new bolts (I just used new zinc plated 10.9 bolts), use antiseize, and don't tighten the hell out of them on reassembly.

[Ashyukun]

Trying to understand what it is you need here. All of those nuts (105615) can be removed from the cages without damage (they just slip into the cage) and they can be replaced. I did it on my own car while doing a frame-off. Got a picture of what exactly it is you are asking about? None of the nuts require bending metal to get in and out.

If you are worried about them seizing up in the future, just replace the square nuts, get new bolts (I just used new zinc plated 10.9 bolts), use antiseize, and don't tighten the hell out of them on reassembly.

Interesting- I'll have to try and see if I can easily slip out one of the nuts that I was able to remove the bolt from (would be nice to be able to not have them on the frame when it's getting blasted & when I have it coated after making repairs).

[Rich]

Trying to understand what it is you need here. All of those nuts (105615) can be removed from the cages without damage (they just slip into the cage) and they can be replaced. I did it on my own car while doing a frame-off. Got a picture of what exactly it is you are asking about? None of the nuts require bending metal to get in and out.

Yes, normally the nuts are easy to get out and back in.

The OP explains in the first post that some of the nuts seized so they spun in the cages during some bolt removal attempts. Now some of the cages aren't cages anymore.

For reference have a look at the photo inserted in the thread. Lots of rustworm action up front, at least. The seized nuts are no surprise in this case.

[Ashyukun]

Yes, normally the nuts are easy to get out and back in.

The OP explains in the first post that some of the nuts seized so they spun in the cages during some bolt removal attempts. Now some of the cages aren't cages anymore.

For reference have a look at the photo inserted in the thread. Lots of rustworm action up front, at least. The seized nuts are no surprise in this case.

Yes, there are several of the nuts that are seized up and the cages are deformed and unlikely to properly hold new nuts (I will be replacing all of the nuts- and likely the bolts as well) so I'll need to either find a way to repair or replace those cages.