Failure analysis: washed out

[swiftdrivr]

Here is something I haven't run into before. The bolts shown are the principle motor mounts on my Swift DB-1. They insert into the bellhousing through the "cups" at the end of the "V" formed by the 3 frame tubes at the bellhousing.{you can just see a sliver of one of the bolts in the photo attached.} As you can see, the washers I used are dished out, and one has worn through. Also, the front top motor mount, where the cross bar bolts to the front of the aluminum head, was also dished out in a nice, neat hole, 1/4 inch deep or so..
My best guess is the washers failed, allowing the engine to "wallow around", resulting in the damage to the front top motor mount. However, the other mounting points seemed okay. [Can't check. Motor still at Rollin's]
I plan to use the AN washer [the new, gold one shown in the photo. It is smaller than the originals, and the center hole is marginally larger] to re-install the motor, but thought I might get other input before I did.
Anyone see anything else to explain this? Any ideas on replacemant washers?

Thanks for the input,

[john f]

For the washer to fold over the bolt head like that the inner surface that the washer sits against is not flat. The washer when loaded by the bolt will conform to both the under head contour of the bolt and the contour that it is against, especially if the washer is a softer or thinner material. I would look at the inner surface of the cup and also make a washer with a thickness at least 3/16 or 1/4" to prevent that from happening again. I would also look at the thickness of the floor of the cup to make sure that it is not too thin. Just my $0.02.

john f

[Garey Guzman]

I had that issue with my DB1. I made steel bushings that just slipped into that cup and used a properly sized AN bolt and washer to retain. That provided better support for the bolt and forces going through that tube junction

[Steve Demeter]

Washers going over relatively soft materials with small bearing area IMHO need to be hard to reduce their tendency to dish. The soft washer could have dished causing the surface it bears against to dish. Depending in the materials involved this could or could not be the case. In any instance make certain that all surfaces like these are flat to start with.

In the trunions on my Citation I use lock washers that are ground on the OD to be a snug slip fit into thee tube. And they are hard. Just torque em flat and the whole mess stays tight. they are thick and hard.

[S Lathrop]

I think you have a bigger problem than just the washers. The deformation of the threads on the bolts are scary as well. My bet is that the inserts in the casting are an issue and they needs to be replaced. In short, every part of that assembly needs to be replaced.

On the newest of my cars, I use socket head cap screws and the threaded inserts are several inches inside the bell housing. The bolts then go through the tr-unions on the engine frame, then through the bell housing to the threaded insets which are inserted from the inside of the bell housing. This setup prevents the threads from seeing any significant vertical loading and the shear loading is quite some distance from the threads.

[steve zemke]

As I recall the flat ends welded onto the tubing to make the mounting bracket was the same thickness as the tube wall. Pretty thin. We cut them out, essentially the bottoms, and welded thicker material in. Then I used hardened washers and AN bolts. Same problem with the front lower outer a arm attachment system. Real bad when the upright separates from the the a arm. A couple of places to beef up on the DB-1

[swiftdrivr]

Thanks everyone. I looked in the cups and although there is some wear on the inside of one, it seems minor, they seem to retain their thickness. The inserts look okay, and I was able to hand-thread a new bolt into each, with no ratcheting, unexpected drag, or looseness once threaded in. I should have put a stack of washers over the bolt and torqued it down, to be sure it held, but I'll do that next time in the shop. I like the idea of thicker, hardened "washers" / inserts [maybe a quarter inch thick?] with longer bolts obviously. I doubt my TAIG lathe is up to working hardened steel. Any ideas about to where I could get them?

[David Ferguson]

I think some of these hardened washers from McMaster-Carr may be just what you need:

https://www.mcmaster.com/hardened-washers

There are milspec washers as well, but I don't know the specification numbers, to know if an MS 20002 or a MS15995 would be what you need.

[roadracer]

Good suggestions above. Replacing the two 7/16 - 20 helicoils in the aluminum module is first on the list. Also, using an aluminum 'spacer' approximately 7/8" diameter with a 7/16 bore and 1 1/8 inches long to fit inside the chassis mounting will make a much better solution. A longer AN7-20 bolt will bring the bolt head out and nearly flush with the outside of the chassis mount so it can now be safety wired. The 'spacer' should fit snugly inside the chassis tube and will eliminate any movement.
Good luck with this!

[Garey Guzman]

After reading Lathrops post, I remembered that I had the bell housing repaired that way too. Then I made steel inserts, similar to this picture. I did something similar to the front rocker arms and stopped killing bearings. Obviously, the front rocker spacers/washers were much thinner than this.

Sent from my SM-N960U using Tapatalk

[john f]

Thanks everyone. I looked in the cups and although there is some wear on the inside of one, it seems minor, they seem to retain their thickness. The inserts look okay, and I was able to hand-thread a new bolt into each, with no ratcheting, unexpected drag, or looseness once threaded in. I should have put a stack of washers over the bolt and torqued it down, to be sure it held, but I'll do that next time in the shop. I like the idea of thicker, hardened "washers" / inserts [maybe a quarter inch thick?] with longer bolts obviously. I doubt my TAIG lathe is up to working hardened steel. Any ideas about to where I could get them?

Get some 4140 pre-hard. (speedy metals come to mind) Turn a fat washer, 1/4-3/4 thick with proper ID/OD to fit sleeve. Heat the pc up to a dull red and drop in water. You'll get a nice hard case with a tough core. Just my $0.02.

john f

[RussMcB]

I think I remember buying longer bolts and using spacers (like thick washers) so the heads were more exposed, and I could use safety wire for extra peace of mind.

[steve zemke]

I used hardened washers, red loctite, and checked the torque every session.

[S Lathrop]

[QUOTE=steve zemke;580350]I used hardened washers, red loctite, and checked the torque every session.[/QUOTE

I would check the torque, with a torque wrench at least once a day when you are running. I think I would forgo the Loctite because when you are checking the torque you will be checking how well the Loctite is performing. You will not be checking how tight the joint actually is. In this situation you have aluminum being clamped between 2 steel parts. Change temperature and the torque on the bolt will change and the clamping force of the joint along with the torque.

Recently I had an upright in my shop where the spindle was trashed because the torque on the outer CV joint was not maintained at the correct level. This allowed the inner races of the bears to move on the shaft of the spindle. The Indication was a loose wheel. The nut was tight but the bearing had worn the shaft so much that I could remove the spindle with hand pressure. My guess was that the Loctite held just fine and the nut never moved until I removed it.

[stonebridge20]

Good suggestions above. Replacing the two 7/16 - 20 helicoils in the aluminum module is first on the list. Also, using an aluminum 'spacer' approximately 7/8" diameter with a 7/16 bore and 1 1/8 inches long to fit inside the chassis mounting will make a much better solution. A longer AN7-20 bolt will bring the bolt head out and nearly flush with the outside of the chassis mount so it can now be safety wired. The 'spacer' should fit snugly inside the chassis tube and will eliminate any movement.
Good luck with this!

This ^

[swiftdrivr]

I've always used anti-seize on these bolts. I torque them [and a list of about 20 other bolts] before every weekend, and in 10 years, I never had a problem until this year.
As for changing the helicoils, I'm not sure how to proceed; I can drill them out and use Big-Certs, but that seems a bit radical considering they seem to be fine, and if I have problems then, it's a huge deal to go from a Big-Cert to strip the bellhousing / ship it / clean / weld up / re-drill / do over / re-assemble. Can you remove a helicoil and replace it with a new one without enlarging the hole? Is it likely to be an improvement if you do?

[Charles Warner]

I've always used anti-seize on these bolts. I torque them [and a list of about 20 other bolts] before every weekend, and in 10 years, I never had a problem until this year.
As for changing the helicoils, I'm not sure how to proceed; I can drill them out and use Big-Certs, but that seems a bit radical considering they seem to be fine, and if I have problems then, it's a huge deal to go from a Big-Cert to strip the bellhousing / ship it / clean / weld up / re-drill / do over / re-assemble. Can you remove a helicoil and replace it with a new one without enlarging the hole? Is it likely to be an improvement if you do?

You do not have to drill out helicoils. They make specific tools for this that work very well. I agree that replacing helicoils with Time-Certs or Big-Certs is a good idea. If you drill out the helicoil you will then have to go up a bolt size. You may not have the room or material to do this.

[swiftdrivr]

You do not have to drill out helicoils. They make specific tools for this that work very well.

I know you can remove a helicoil, but I don't know if you can then replace the one you removed with a new one, using the same hole, without drilling out the hole, and will that improve things. I'd rather not drill unless there is no other option, as it limits my later options.

[Charles Warner]

I know you can remove a helicoil, but I don't know if you can then replace the one you removed with a new one, using the same hole, without drilling out the hole, and will that improve things. I'd rather not drill unless there is no other option, as it limits my later options.

If you get the helicoil out smoothly you can try a bit of loctite green with the new helicoil. It should fit fine and be set. It's worth a try. If you drill out the helicoil replace it with a Time-Cert or Big-Cert. They are much better.

[Gary_T]

It is a bit of a PITA, but you can safety wire those bolts with them inside the cup, instead of creating a large spacer to bring them out.

I'll be putting my engine back in my SE-1 in the next week or two. I will look at incorporating some thicker, hardened washers on those bolts.

Gary

[steve zemke]

[QUOTE=S Lathrop;580354]

I used hardened washers, red loctite, and checked the torque every session.[/QUOTE

I would check the torque, with a torque wrench at least once a day when you are running. I think I would forgo the Loctite because when you are checking the torque you will be checking how well the Loctite is performing. You will not be checking how tight the joint actually is. In this situation you have aluminum being clamped between 2 steel parts. Change temperature and the torque on the bolt will change and the clamping force of the joint along with the torque.

Recently I had an upright in my shop where the spindle was trashed because the torque on the outer CV joint was not maintained at the correct level. This allowed the inner races of the bears to move on the shaft of the spindle. The Indication was a loose wheel. The nut was tight but the bearing had worn the shaft so much that I could remove the spindle with hand pressure. My guess was that the Loctite held just fine and the nut never moved until I removed it.

I can only tell you what my experience was with my DB-1, serial number 14. The two big bolts were constantly loosening up. When I torqued them to 200lbs., as I recall the value, and used the red Loctite, they longer loosened up. I know many people do not like loctite, but when used correctly I have always had the results I was hoping for. May not have been ideal, but it worked for me. Anti-seize will not give a true torque value.

[J Leonard]

What size are those bolts?
What grade or rating is the bolt with the deformed threads?
How long is the Helicoil threaded insert, maybe use same only longer.
Take a look at "stud washers" for dimensions. About .156 thick.
I know their not AN/NAS but 12 point flange screws can be handy if the shank and threads work. The alloy heat treated ones that usually have the manufacturer I D stamped on the head.

[swiftdrivr]

What size are those bolts?
What grade or rating is the bolt with the deformed threads?
How long is the Helicoil threaded insert, maybe use same only longer.
Take a look at "stud washers" for dimensions. About .156 thick.
I know their not AN/NAS but 12 point flange screws can be handy if the shank and threads work. The alloy heat treated ones that usually have the manufacturer I D stamped on the head.

From memory, I think they are 7/16 - 20. I know that they are AN bolts from Pegasus. I actually didn't notice any damage to the threads, but Steve, who is a lot better engineer than I, thought they looked bad.

[swiftdrivr]

[QUOTE=steve zemke;580372]

I can only tell you what my experience was with my DB-1, serial number 14. The two big bolts were constantly loosening up. When I torqued them to 200lbs., as I recall the value, and used the red Loctite, they longer loosened up. I know many people do not like loctite, but when used correctly I have always had the results I was hoping for. May not have been ideal, but it worked for me. Anti-seize will not give a true torque value.

I've always torqued them to 35 ft/lb [might be 45, don't have my notes with me.] Never an issue until this year. I don't think torque was the root problem, but I would think 200 was way over-torqued.

[Daryl DeArman]

From memory, I think they are 7/16 - 20. I know that they are AN bolts from Pegasus. I actually didn't notice any damage to the threads, but Steve, who is a lot better engineer than I, thought they looked bad.

Those threads are toast. If you look at their profile the crest of each thread has yielded towards the non-head end of the bolt.

I would utilize a proper strength fastener with a hardened washer of the correct ID/OD, ensuring the top and bottom profile matched their mating surfaces.

[Jon Jeffords]

Also, using an aluminum 'spacer' ... to fit inside the chassis mounting will make a much better solution.

I believe you want that fat washer / spacer to be made of steel, so as to reduce the amount (length) of compression in the washer. We're probably only talking about 0.000X of an inch difference, but it should make for a more robust clamp joint than an aluminum washer. Ideally, you want the bolt to stretch when torqued up, NOT the washer to compress.

[CGOffroad]

After reading Lathrops post, I remembered that I had the bell housing repaired that way too. Then I made steel inserts, similar to this picture. I did something similar to the front rocker arms and stopped killing bearings. Obviously, the front rocker spacers/washers were much thinner than this.

Sent from my SM-N960U using Tapatalk

I will second what Gary has said here. I had a DB-1 and presently have a DB-3. Both cars have had a large spacer as shown in this picture on the bolt. It fits snugly in the hole and the head of bolt sticks out of frame just a bit. I use a little blue loctite when replacing bolt and I put safety wire through bolt head. Have not had any problems with this connection point to date.

[swiftdrivr]

Okay, I got to spend a little time in the shop, and one of the inserts was "not as advertised". When I threaded the bolt in tight, it seems loose. So, EZ-loc and Time-serts won't work to replaced a failed heilicoil, so I ordered BIG Serts, which are on the way. I also ordered some 3 inch pieces of 8620 ChroMoly. I need to find someone who can turn me some 1/4 thick by 0.8 inch diameter spacer / washers, and figure out the new bolt length, and if things go well, I think I can fix this thing, hopefully in time for the Jim Stark Memorial / Quartermaster classic at Roebling. Thanks for all the advise!

John, thanks for the "speedy metals" tip. Saved me about 15 bucks over online metals price!