Crankshaft thread size/ die size?

[pat777]

Can anybody tell me what size die should be used for cleaning/straightening up the threads on a 1964 Century please? We have a loose base plate so we need to take off the flywheel, a few heavy blows with a lump hammer have taken their toll on the threads and a new dome nut will be required and the flywheel unsurprisingly is still stuck in place. Oh the joys of seagull ownership...!

Cheers Pat

[Stelios_Rjk]

It's 7/16x18 BSF.

[pat777]

Thanks Stelios_Rjk

[Stelios_Rjk]

More than welcome!
Have you found the procedure to be followed to remove the flywheel? Piston on BDC and soaking the joins in penetrating oils etc.

[pat777]

Yes lots of previous discussions on the subject of flywheel removal read through. Plenty of wd40 used to try and free it up a bit. Going to try some heat on it next time we are tackling it. There does seem to be a flaw in this method of hammering the nut down on the crankshaft, not only the risk of bending the crankshaft but also damaging the threads on the dome nut and the crankshaft. Oh, if only the engineers in seagull had designed the flywheel to be removed with a puller, things would be so much easier! I'm sure I would find something else to complain about pretty quickly. Ah, sure it would be no fun if it was easy.

The instructions in the manual say to screw the dome nut all the way down before hammering down, but I saw mention in one of the previous discussions of only screwing the nut down a few turns. I guess I'll follow the instructions in the manual and screw all the way down in future attempts. I was wondering would it be better to use an over size dome nut on the crankshaft for this purpose, so as to avoid damaging the threads on the crankshaft. I guess it is standard practice among fellow seagullers to use a die to clean up the threads on the crankshaft after this flywheel removal procedure and replace the dome nut with a fresh one.

Cheers Pat

[Stelios_Rjk]

You have to screw all the way down the nut. Piston on BDC position when hitting the nut. A steel nut is just what you need. And patience. A lot of it. I soak the joins sometimes even for a week or so. WD40 doesn't have a place in my workshop by the way. There are a lot better products than this marketing creation.

[pat777]

WD40 doesn't have a place in my workshop by the way. There are a lot better products than this marketing creation.

Thanks Stelios_Rjk, so are you going to share with us novices, the names of these "better products" or are they home made concoctions.(secret family recipes)

I guess the more soaking the better and lots of patience.

Cheers Pat

[Gannet]

I don't know if it helps, but I put a small steel ball on top of the crankshaft and then tighten the dome nut down onto the ball.
My thinking is that this will transmit the shock loading from the hammer blow directly onto the end of the crankshaft, rather than via the threads. This will reduce the chances of damage to the crankshaft threads. Possibly?

Jeremy

[Stelios_Rjk]

Sure, I have no problem sharing, just because of brands etc I didn't mention it. I use permatex super penetrant 80052. If you want a homemade recipe then heat the point until oils are gone and then quench with coke. Not diet coke, the regular. I have freed two gearboxes so far this way. It's the phosphoric acid it contains that do the miracle. The problem with the flywheel is that the key path drives any liquid to the stator plate, it would be better if we could close that path just before the end. Liquids could stay there to react more efficiently.

[phil]

Not sure of what is available over there, but here is what most in the Antique Outboard club over here use. Some are easier to source than others. Both Hoppes and Gibbs gun oils are used by some who really seem to like the results. Most only use WD 40 for wiping down the exterior of the motor and cowls etc.

http://www.fordbarn.com/forum/showthrea ... &showall=1

The 50/50 automatic trans fluid and acetone seems to work well for most who try it. Remember that acetone evaporates quickly ( mix small batches) and has a reputation as a carcinogen as well as being very flammable. Be careful.

For parts stuck by rust, the penetrating oil let sit for a while, and an air powered tool with a blunt end and a hammering motion is very effective in freeing rusted parts. Some have used it most effectively on driveshafts stuck in the bottom of crankshafts.

Also penetrating oil let sit a while and alternating heat and cold can be effective.

Coke is ok, but thinned out molasses 50/50 water molasses is as effective and much cheaper. I would rather use them to soak small rusted parts in a container than directly on a motor, especially if heat is to be used, could be a sticky mess.

[pat777]

Thanks Gannet, that's a good tip and seems as if it should work to protect the threads. Also thanks to Stelios_Rjk and to phil for the tips on the penetrating fluids etc. It turns out we were not using wd40 but rather "plus gas" penetrating oil, they're are both in a blue can and I wasn't the one doing the squirting, hence the confusion.

Cheers Pat

[charlesp]

Plus Gas is an excellent penetrating oil, it's thin and it creeps very well. Having said that I don't use potions and oils for flywheel removal.

Usually a distorted crankshaft nose after flywheel removal is associated with using too small a hammer in repeated blows rather than a good shrp blow with a good sized tool. I am one who favours backing off the flywheel nut just a little bit. The nut must be a steel one.

[pat777]

Thanks charlesp. Yes it was you I had seen mentioning not tightening the nut fully down in previous discussions. That's why I thought I'd mention it here. What is the logic behind your method? Is it a case of just not liking following the rules as written down in the seagull service manual. I have to say I do like gannets method of using the ball bearing. And yes we were using a brass dome nut, doh! Steel nuts in future, hopefully we won't be doing this again for a while.

Cheers Pat

[charlesp]

My method isn't actually mine, it comes from the chap who for years ran British Seagull's repair operation in Poole.

If you tighten the nut down then the shock (which as I have said has to be a decent whack!)transmits itself partially to the flywheel itself, which therefore moves as well as the crankshaft.

A partially backed-off nut (steel) will transmit the shock to the crankshaft only, the inertia of the flywheel restrained by hands/rope etc imparts a separating effort. Voila!

I haven't had to resort to any snake oil style things, they all come apart after a good whack (sometimes more than one). The whacking motion must be smack on the nut, in line with the crankshaft. The only exception is the electronic ignition flywheels, where witchcraft as well as force is required.

[pat777]

Thanks charlesp for explaining your methods in more detail. Interesting also that this was the method used in the seagull service department. It has started budging a small bit now, I guess we'll carry on, but it has had a lot more than two blows with a 4lb lump hammer at this stage. We'll try heating it up again and have another bash so to speak. Thanks for sharing the insider tips.

Cheers Pat