connecting rod fastener locking device

[Kevin Johnson]

There are a lot of modern different methods. Patent search is your friend.

The reason you will not see these in shops is the equipment and/or machining methods are very expensive.

The way that you track this information down is to start with a connecting rod bolt patent: there are many of them. Then look at the "cited by" section and thread your way back into the current era. Good grief, people, Chinese patents are now translated automatically for you. I remember having to travel to a Patent library and do a manual search. Don't get lazy.

How many shops are using electron beams or lasers to tack the bolt to the rod body, for example:

https://patents.google.com/patent/DE102004025932A1/en

[Zmechanic]

I have seen some older flat 6 aircraft engines that use safety wire on rod bolts. Given the assumption that under-torqued rod bolts are one of the leading causes of failures I'm not sure how much that helps, but who knows.

Nordlocks or Spiralock threads are two of the only real mechanical ways I know of to truly keep a thread secure AND torqued without chemical threadlockers, other means, etc in harsh, high vibration scenarios.

[modok]

yeah but WHY would the rod bolt come loose?
Things don't happen for no reason. There will be a cause, and it will be measurable. The bokt will have to stretch, or the ting it's in will have to shrink. One or the other will ahve to happen and it will be measurable.
Superstition goes away when you start measuring things.

A rod bolt is not the kind of joint that can come loose easily. The cure for a lot of situations where fasteners DO come loose, is to re-design it MORe like a rod bolt.
Axle bolt VS bolt in spacer.
An axle bolt has almost no stretch. If .001 of material mushroioms out under one end, it's gone from tight to 100% loose.
Now, replace that with a piston pin with a bolt through the middle. Tighten this, the bolt stretches .005, and the pin compresses .005, .010 of material will have to move before it's loose. That's the difference. That's how you do it.

[PackardV8]

Let's also mention, back in the dawn of the design of ICE rod bolts, the torque wrench was a rare and exotic tool, not found in home shops and not in most small town garages and dealerships.

jack vines

[modok]

The question was about engine still in real use, on roads.

I bet there are many bulldozers still in real use, but not on roads, maybe, making roads.

[enginenut2]

Friends and I just completed a first overhaul, brought on by a water pump coupling failure that caused piston damage, then many years of non use, of a 1956 Seagrave v-12 flathead. 531 cu in, twin ignition, dual carburetors, and I think the cleanest design v engine of it's era. This engine was designed and used initially by Pierce-Arrow in approx. 1930. Seagrave used them in their apparatus , buying all needed to continue manufacture after P-A folded in the late 30's. Used P-A size of 462 cu in until increasing the bore to raise to 513 sometime in the 50's. The robust crankshaft and rods looked like v8 Chevrolet and had lock wired main bearing bolts and cotter pins in rod bolt/nuts. We never found reliable bolt torque specs but used similar examples as a guide. It's hard to settle at an exact torque setting and have the pin/holes align when using cotter pins. Original design had Hyd lifters like flathead Cadillac running in bolted in bronze blocks of 6. Combustion chamber was relieved like the old racing flathead Fords and the head was shaped like Ricardo wanted flatheads to be.The bank angle was 80 degrees not 60 but paired 2 rods on each crankpin, Each delco dist had a set of contacts firing it's coil for 1 bank of 6 and another contact set firing it's coil for the other bank---synchronization was effective byt interesting ---and then there is the other similar distributor.Seagrave said you should run 1 dist or the other but not routinely both together. We modified Perkins diesel bearings since they had same crankpin diameter and rod bore. Bore 3 3/4 so 261 Chevrolet rings worked and the 1 valve we needed was cut down from a F 20 Farmall. Seagrave rated this thing at approx. 230 Hp @ 3800 RPM. We have it mounted on a small 2 wheel trailer w/radiator and will take it to some engine shows this year just to stir a little public opinion. Sure sounds sweet and smooth as a mouse in a meal barrel.

[cjperformance]

Friends and I just completed a first overhaul, brought on by a water pump coupling failure that caused piston damage, then many years of non use, of a 1956 Seagrave v-12 flathead. 531 cu in, twin ignition, dual carburetors, and I think the cleanest design v engine of it's era. This engine was designed and used initially by Pierce-Arrow in approx. 1930. Seagrave used them in their apparatus , buying all needed to continue manufacture after P-A folded in the late 30's. Used P-A size of 462 cu in until increasing the bore to raise to 513 sometime in the 50's. The robust crankshaft and rods looked like v8 Chevrolet and had lock wired main bearing bolts and cotter pins in rod bolt/nuts. We never found reliable bolt torque specs but used similar examples as a guide. It's hard to settle at an exact torque setting and have the pin/holes align when using cotter pins. Original design had Hyd lifters like flathead Cadillac running in bolted in bronze blocks of 6. Combustion chamber was relieved like the old racing flathead Fords and the head was shaped like Ricardo wanted flatheads to be.The bank angle was 80 degrees not 60 but paired 2 rods on each crankpin, Each delco dist had a set of contacts firing it's coil for 1 bank of 6 and another contact set firing it's coil for the other bank---synchronization was effective byt interesting ---and then there is the other similar distributor.Seagrave said you should run 1 dist or the other but not routinely both together. We modified Perkins diesel bearings since they had same crankpin diameter and rod bore. Bore 3 3/4 so 261 Chevrolet rings worked and the 1 valve we needed was cut down from a F 20 Farmall. Seagrave rated this thing at approx. 230 Hp @ 3800 RPM. We have it mounted on a small 2 wheel trailer w/radiator and will take it to some engine shows this year just to stir a little public opinion. Sure sounds sweet and smooth as a mouse in a meal barrel.

Fantastic, id love to see some pics of that. Cool old stuff.

[dwilliams]

Seagrave said you should run 1 dist or the other but not routinely both together.

Interesting! I wonder what the reasoning was on that...

[peejay]

I wanting to think I seen something that had the rod nuts cotter pinned. I can't remember what

I rebuilt a Continental flathead six from a forklift that had cotter pins in the rod nuts. Well, five of the six rods had cotter pins, anyway. The odd man out had undrilled rod bolts, so the nuts had no cotter pins.

If the nuts are properly torqued, there should be no reason to lock them in place. Locking devices are for nuts/bolts that must be undertorqued for assembly reasons (wheel bearings, etc)

[Keith Morganstein]

When I started rebuilding engines as an apprentice, I asked the guys why the rods didn’t have locknuts. I was told the (regular) rod nuts were special lock nuts.

When I stated rebuilding Diesel engines, many of the older engines had fasteners with sheet metal locking tabs that you bent against a flat on the bolt head. Sometimes I’d pull an engine apart and find a bolt with the sheet metal tab in the oil pan. Again I asked what was up with that. I was told, “if a bolt wants to come out, that tab isn’t stopping it” everyone continued using the tabs if the engine called for them, but I don’t see them on newer engines.

[dwilliams]

I have encountered self-locking rod nuts before, but I suspect they were ordinary nuts before some bozo cross-threaded them down with an air tool...

[enginenut2]

Seagrave said you should run 1 dist or the other but not routinely both together.

Interesting! I wonder what the reasoning was on that... DWILLIAMS, Pierce Arrow only used single plug per cylinder. I have noticed in older fire apparatus there was a lot of effort toward reliability like redundant starting methods, ignition, etc. I have seen 1 fire truck gas engine, probably early 20's, that had 3 plugs per cyl---1 double firing magneto and 1 conventional magneto. This seagrave had plugs necessarily located in different spots of the non-symmetrical comb chamber. Search on youtube for seagrave 531 v-12 engine and the plugs can be seen one higher in the chamber than the other. These engines with 2 intake manifolds only connected by two 3/4" tubes and EACH distributor acting like 2 individuals-each firing half the engine, must be touchy to synchronize at small loads and throttle openings. Quote from a Seagrave operation manual: " It is not recommended that both ignition switches be on at the same time as this sometimes results in engine roughness. They should, however, be alternated in use to make sure that both systems are functioning properly at all times." I can see room for error with each separate ignition system having it's own mechanical advance mechanism and the difficulties of maintaining gap/dwell/timing for 4 sets of contacts.

[tresi]

I have seen some older flat 6 aircraft engines that use safety wire on rod bolts. Given the assumption that under-torqued rod bolts are one of the leading causes of failures I'm not sure how much that helps, but who knows.

Nordlocks or Spiralock threads are two of the only real mechanical ways I know of to truly keep a thread secure AND torqued without chemical threadlockers, other means, etc in harsh, high vibration scenarios.

Yea, I seen a lot of aircraft engines with safetied rod nuts but I left them out because they were aircraft. Trust me I spent much more time safetying aircraft hardware than installing them. I've had T.I.'s that insist that the only way to install a cotterpin was to cut 1 end the lenth of flat of the nut from edge to the pin hole and fold this end flat and tight aganst the nut. The other end was to be folded over the end of the bolt and neatly tucked in the unused slot near the the head of the cotter pin. If he could catch his finger on the end of a cotter pin he'd pull it out and make you repin it.

[modok]

I have built many vintage engines with locking devices, but if allowed i get rid of them, because we know now they cause more problems than they solve.
Split lock washers damage the surfaces and likely to crack, and cotter pins and safety wire tends to fall off and go through the oil pump.
At least put magnets in the pan to catch them when they fall off.
The biggest PITA for me is old 235 chevys with lockwashers on the main caps. Each time you loosen the bolt, it damages the surface. If it gets dished bad enough it will actually split the main cap, crack it down the side. I re-face the bolt surface flat, and made my own solid washers that I use . if they will not buy my washers i take the lock washers and round the sharp points do they don't damage the caps further.

There are joints that need safety wire ect, but rods and main caps are not the type of joints that need it.
Worst case is probably a piece of sheetmetal affixed to a solid casting with a screw. Almost no stretch, highly susceptible to vibration.

[Zmechanic]

Btw I totally agree rod bolts should not need locking devices. When properly preloaded and applied, the forces during running should never exceed and cancel out the clamping preload, so the bolt stress is essentially constant = no loosening.

Now undertorque one and it's a while different story.