Crankshaft wear question.

[rgh0]

I think the suggestion is :

1. The clamping force MAY be insufficient in some circumstances causing the flywheel to shift a small amount on the crank. The lack of the press fit on the crank hub removes some of the ability of the flywheel to carry the torque from the crank.
2. The flywheel may not stay centred on the crank if it shifts and is not a tight fit on the crank hub and this could lead to run out and loss of balance and ultimately bolt failure.

Dowels will help in both these circumstances to avoid movement, fretting or an off centre shift leading to run out and loss of balance. Personally I would prefer to maintain the fit on the hub, but if it works and its your personal preference as it appears to be for some to have dowels for centering on the the crank and not the hub fit then go for it.

cheers
Rohan

[Lyn7]

Hi all, an interesting discussion. I wonder how much value the light interference fit is, in actual fact? I can see it's value to centre the flywheel, but would have thought it of little value in actually keeping the thing in place. I would have thought the clamping force of the bolts together with dowels would be more than sufficient if fitted correctly.
I would certainly like at least 2 if not more dowels, but maybe the bigger factor is the question of smooth driving or being a hooligan . Horses for courses. I use an aluminium flywheel on one engine surely this is more likely to be held in place by the 4 bolts and 4 dowels? I also like loctite on the threads.
Lyn...

[Craven]

dougal9887 asked, is there any solution.
The proposed solution to reduce the diameter to a good working surface ensure concentricity by additional dowels, may not be the best it is just one. Both 512BB and myself have successfully used this method in PRACTICE, nether have experienced long term adverse problems, in my case a T/C for S2 Seven back in 1985 which I had for 20 years.
Reclaiming any damaged component more often than not involves a compromise of some sort, the perfect solution may not exist but ultimately Dougal will need to decide what course of action to take to reclaim this otherwise unserviceable crank.
Ron

[oldchieft]

Reclaiming any damaged component more often than not involves a compromise of some sort, the perfect solution may not exist but ultimately Dougal will need to decide what course of action to take to reclaim this otherwise unserviceable crank.
Ron

As I said before, metal spraying and re-machineing, that seems dam close to perfect.

Jon the Chief

[AHM]

In order to achieve correct balance runout etc. The flywheel needs to be mounted within a set tolerance. Where it is clamped in position by 4 or 6 bolts.

The suggestion from my side is that location is achieved by the fit between the large diameter of the crank and the recess in the flywheel. a simple set of tolerances between A and B (Clearance) C.
I measured this as 0.0005" but I'm only measuring with a digital vernier so neither I or it are accurate enough. Assuming accuracy is 0.001" so if we assume the opposite extreme on each part we get C= 0.002" rather conveniently the limit of runout!

For simplicity consider one screwed joint. Ignoring the tolerance of the bolt this would be C/4.ie 1/4 of the tolerance for the same result.

But there are 6 bolts evenly spaced on a PCD so the tolerance of each must be much tighter in order to maintain the same location tolerance of the flywheel on the crank - consider opposite ends of the tolerance for each set of holes.

The tolerances would need to be so tight that the parts would be expensive to manufacture and difficult to assemble for no benefit in end result.

So I'm suggesting that the location is achieved in on the outer diameter of the crank, and that the tolerance of the bolt holes is opend up to suit the sum of the errors. ie cheap to make and easy to assemble. Those bolts aren't tight are they Leslie. C=0.020" on the one I have here.

Just my theory - Happy to be proved wrong. I expect some of my maths is wrong the reference I used switched between clearance, tolerance, and error, and who knows the engine I have here may have been fiddled with, by someone like Leslie, before I was born!

[promotor]

Just to throw my fat into the pan - a 4 bolt crank and flywheel doesn't rely on the press fit of the flywheel, and only uses one dowel so in effect there are only five points of contact and no "spigot".

However if it were me I would fit a Speedi Sleeve as they are longer lasting, and probably cheaper than having the crank seal surface ground, and can be installed by yourself without having to cart it off to a machine shop that may or may not do a good or timely job.

EDIT : The 4 bolt crankshaft does infact have a small spigot so it would seem my comment isn't relevant!

[dougal9887]

Well, this turned into a fascinating thread! What a great forum and thanks for all the replies. As ever, there are a number of opinions as opposed to a definitive answer and of course all are valid. As stated it's now up to me to decide on my course of action. So here are my thoughts.

Metal spraying and re-machining. This is probably the best engineering solution to provide an as new surface. But I hardly dare think of the cost. And it's not as if it's a load bearing surface. We're only trying to keep the oil in and dirt out.

Machine down to a new smooth finish. I personally don't think I would like to lose the interference fit for the flywheel especially since the bolts were sheared, many years ago, and the holes were slightly damaged as a result. There have been no consequential problems however in the current format. I suppose that the full diameter could be retained for the flywheel section and the remainder stepped down to a new smooth finish. However, the type of finish appears to be important and this may or may not be acheived. I'm also developing a machine shop phobia.

Speedi-Sleeve. A simple solution to a simple problem. Why make life more complicated? Chosen sleeve arrived today!

Still on the subject of wear, I checked the crank journals and pins with plastigauge prior to removing the crankshaft and the running clearances were within those given in the manual. Now I've had the micrometer on them, the journals are 3 tenths of a thou' (@ 2.1052") and the pins 4 tenths of a thou (@ 1.9366"), less than the minimum sizes stated in the manual. This must be expected with wear of course, and there is some very light scoring. As the running clearances are within tolerance, and bearing in mind, no pun intended!, that the milage will be low, can another trip to the machine shop be avoided? The crank is on a .020" regrinding but could go one more to .030" if necessary.

Thanks again for all the help.
Dougal.

[promotor]

I have used cranks up to 0.0015" under the bottom tolerance on mains and big ends by using a high pressure high capacity pump with no issues whatsoever over 10,000 miles. I'm sure you'll be fine with 0.0004". Interestingly the main bearing size @ +020"on a crossflow engine (which is obviously very closely related to a T/C) is 2.105-2.106" so with a crossflow crank you'd still be in spec by 0.0002".

If you have light scoring you can get rid of that with an appropriate grade of wet or dry. I normally mount a crank in a block and rotate it (ratchet with 5/8" socket on the sprocket bolt) while applying pressure to the journal with the wet or dry (lubricated with paraffin or oil) - using an old bearing to press the sandpaper down squarely onto the crank normally works well but anything that allows you to press the sandpaper evenly onto the journal will work. To do the big end journals I use a con rod with sandpaper - split the cap from the rod and use the main part of the con rod and with the housing apply pressure to the big end journal.

Remember to rotate the crankshaft in a clockwise direction (ie normal engine rotation direction) if polishing the journals with this method as it makes the iron "grain" lay in the right direction. Use 1500-2000 grade wet or dry to finish.

There is a better way but you would need to mount the crank in a lathe with the crank rotating and then use some sort of belt sander (without a wood floor cleaning type belt!!) to polish the journals.

[gjz30075]

Would the Speedi Sleeve prevent the flywheel from fitting on the crank? If its a snug fit now, what happens when you add a few thou?

[dougal9887]

Thanks for the replies.

Promotor - glad you mentioned the xflow tolerances, this IS a xflow crank! (tall block conversion). So I'm still within tolerance! So is it the case that I would either just put it back together unpolished with the existing shells or else polish the journals and use new shells.I think machine shops can also polish using special tongs, is that right? Do you happen to know the big end tolerance for the xflow?

GJZ The Speedi-Sleeve presses on past the flywheel mounting so avoiding that problem.

Dougal.

[promotor]

Maybe if you post a picture of the bearings and journals we can give you an idea of whether it needs dealing with.
Bearings and cranks always get running marks in them so you could just have got normal wear.

Machine shops can polish using tongs but they may not keep checking the size as they polish them - they may just keep going until the marks are out. But if you are going to use a high pressure high capacity pump (don't just fit a high pressure only pump as looser clearances need more flow by way of higher capacity to keep the bearings lubricated as the losses are slightly more) you will most likely be fine. Obviously you could polish the surface and get rid of high spots but still leave slight grooves - I don't see slight grooves as too much of a problem as they don't stand proud and damage will be minimal under running conditions. Again, a high pressure high capacity pump helps with most scenarios you can throw at them.
The only thing to remember about the high pressure side of an oil pump is that you won't see any higher pressure at idle when the oil is fully warm when compared with a standard pump but you will see an increase in pressure at normal "higher" running speeds. However the higher capacity should be seen right from idle as the rotor moves more oil per oil pump shaft rotation.

The xflow sizes are 1.937-1.938" @ STD which is the same as Lotus on the small end of the size but 0.0005" larger on the top end - but as you say a combination of undersize journals with "in-spec" clearances won't be an issue.

[john.p.clegg]

Dougal

I hope you're going to post some piccies of fitting the sleeve....

John

[dougal9887]

Here are the piccies of fitting the speedi sleeve.
The product ref. was 99311 supplied by Barnwell.co.uk next day for around ?35.
At first sight, at least one other sleeve listed seemed a more appropriate size, however this seemed the best compromise. The sleeve is narrow enough to be pushed back from the flywheel, however the position at which the lip of the seal contacts it is very close to the sleeve's flange break-off groove so I did indeed break off the flange and push the sleeve right up to the shoulder on the crank. Since I didn't have anything with a tight enough fit to drive the sleeve further on I used a large jubilee clip, well tightened, and gently tapped it around its circumference until the sleeve arrived at the shoulder. Wellseal was applied to the crank before fitting the sleeve.

Speedi sleeve and fitting tool.

Breaking off the Speedi sleeve flange.

Using a jubilee clip to drive the Speedi sleeve further onto the crank.

Speedi sleeve fitted.

I also decided, on the advice from the machine shop, to have the crank reground and the flywheel surfaced. Here's the assembly back from bring balanced.

Reground and balanced crank assembly.

Dougal.

[gjz30075]

Good writeup! Thanks

[john.p.clegg]

Dougal

Nice...

Thanks
John