Square Four MkI restoration complete - almost....

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john.whiting
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Re: Square Four MkI restoration complete - almost....

Postby john.whiting » Tue May 14, 2019 7:48 am

I had a liner drop in the works ute...a 1986 2.2 diesel Mazda ..........it must have cracked the flange ,and dropped down over the rod,getting busted into a million bits........Oddly enough ,the motor kept running ,and as I was on the freeway,I didnt stop.I was able to drive home ,about 2 miles ,and apparently nothing else broke.......The business was in the process of being sold ,and the partners were P/O d ,because it wasnt included....value maybe $1500,in a $3 1/2 million deal......anyhoo ,it saved me from trying to get a roadworthy cert on a total wreck.......bit embarrasing when the ally tray was sold ,and a flogged out uni was visible..........what they say about the mechanics vehicle?

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Re: Square Four MkI restoration complete - almost....

Postby Gui.dorey » Wed May 15, 2019 10:12 pm

Hi Chaps,

So finally got to the bottom of it. Literally! The endoscope showed nothing broken and I had tears running down my eyes like a little 8 year old girl as I disassembled my engine all the way down to splitting the cases.

Everything was free except the front crank which even after taking out the coupling gears wouldn’t budge a bit. The plain bearing bush had seized completely. Here are some pics after 30mins of hammering the crankshaft out of the bush. That’s how seized it was! It probably melted and soldered itself to the crank. Fortunately the crank is fine and no further damaged occurred. Probably because I was just coasting to my house and likely had already pulled the clutch lever, so the engine just died as it seized.

The question is now why? Lack of oil supply? All the passages are free - I just checked. Were the oil holes on the bushes in the wrong positions? It shouldn’t matter because the bushes have a groove on the outside. Anyway, I had the bush for the rear crank with the holes at 12 and 6 o’clock, and for the front one at 3 and 9 o’clock. And when I was building up the engine I had checked if oil would reach the front bush by pumping oil into the passage to the rear bush, and it did. What’s the current wisdom on this?

Was the clearance too tight? After assembling the cranks, everything turned smoothly.

As it was basically the first test run, and of course running the engine in, I didn’t push her - no high revs, no high speeds, just tucking along really. The engine was warm but much less than I expected from all the stories here - I could touch the head with my hand a few minutes after the engine stopped, so temperature could not have been a problem.

The rear bush is absolutely fine.

Hopefully Draganfly has a bush in stock, and then will have to figure out where to get an inline bore. Last time had to send everything to England and wait over 6 months to get them back. Nobody would even touch the job around here.

I’m going for a very large drink and off to bed :(
Gui
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simon.holyfield
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Re: Square Four MkI restoration complete - almost....

Postby simon.holyfield » Wed May 15, 2019 10:22 pm

Well done Gui, I feel your pain but it could have been a lot worse.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
http://ariel-square-four.blogspot.com

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pauldridge
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Re: Square Four MkI restoration complete - almost....

Postby pauldridge » Wed May 15, 2019 10:44 pm

I guess it could have been much worse, but still not fun having to strip your entire engine. nevertheless, it always goes quicker the second time around!

I had similar difficulties finding someone here in the states that can competently line bore those bushings, there seems to be just one guy left in the entire US.. up in Maine, and he took a good 6 months as well. The bushings that D'fly provides have a very thin lining/coating inside. My first one was destroyed by the first machine shop who attempted to bore with a drill.. the lining just peeled off. On second shot with my Maine guy, he insisted on turning the bushing to his own specs, from brass stock. So far it is working beautifully.

As to cause, I would be seriously looking at clogged oil passages. Last year, I rebuilt the engine in my MGA roadster. Upon completion, it started up and purred immediately on first try. Then I went for a short drive.. didn't get 100 yards down the road when the engine seized, with clutch in, just like you have described. Drug the car back to the shop, and just like yours, that crank just refused to turn. Pulled the pan off, and turned out a rod bearing had seized, and it was definitely due to crud in the oil passages, which blocked flow to that one bearing. I foolishly had not pulled the oil galley plugs and properly cleaned the inner passages. Of course, that oversight required a complete teardown of the engine and re-assembly. Likewise, my crank wasn't seriously damaged.. just a quick polish and it was ready to go back together with standard bearings (it was a brand new crank)

My own Ariel engine "guru", who fastidiously cleaned the crank passages, as well as the rocker shaft oil ways and all others, advised me to change the oil after an initial static run of just 10 minutes, to which I complied.

Do you have a oil filter installed? Very inexpensive, and not that difficult to install.

Good luck with it, and keep us posted.

PS.. I do believe I have a pair of brand new, unused timing side crank bushings from D'fly that I didn't use, due to the machinist's insistence on rolling his own. I'd be happy to turn them over to you gratis, but I find that inexplicably, mailing or shipping from here in the US to the UK is atrociously expensive. Maybe less so to other parts of the E.U.?
Phil Auldridge Austin, Texas - USA
Visit the North America Ariel forum: http://arielnorthamerica.org/phpBB3/
53 SQ 4 MK II, '72 Norton Commando, '78 BMW R100/7, '79 Honda CBX, 2014 Indian Chief Vintage

Gui.dorey
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Re: Square Four MkI restoration complete - almost....

Postby Gui.dorey » Thu May 16, 2019 6:03 am

Hi Phil,

Many thanks for the offer, that really very kind of you. I wouldn't know that shipping to other parts of Europe would be different to the UK, but you could always ask what are the charges to Germany. Just say it's an emergency air lift because the Russians are coming or something :) Anyway I'll ask Drags if they have some in stock at the moment.

Still not sure why it happened. The oil passages are free - I can push a pipe cleaner through the passage from the front to the rear bush and it comes out clean. The only thing I could think of would be a bad alignment of the oil holes on the bushes, but that seems to me to be very unlikely.

Do you know the specs of your brass bushes? What clearance did he use? And what are the advantages/disadvantages of doing them out of brass instead of the originals with white metal?

Cheers
Gui

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Re: Square Four MkI restoration complete - almost....

Postby john.whiting » Thu May 16, 2019 6:09 am

I always flannel moly dag into the fresh ground surface of a journal...........bearings generally pick up in a spot then ,heat causes expansion and seizure for the whole bearing....its not always caused by lack of oil,but usually.............sometimes things can run for ages,then seize......but smearing all rubbing surfaces with molydag is always good practice........or you can use one of the special breakin lubes the engine builders always give you with new grind and bearings.......never assemble a bearing with just engine oil,the fresh polished bearing is oil repellent,and oil wont stick......but never get moly on the back of a bearing,or it may spin.

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Re: Square Four MkI restoration complete - almost....

Postby john.whiting » Thu May 16, 2019 6:14 am

If you have a brass/bronze bearings seize ,the journal will be cut and ruined.....white metal runs and frees the bearing.......the other issue is dirt is able to embed in white metal without scoring the shaft......with bronze ,the shaft scores unless it is very hard.Even trimetal bearings are tin plated for breakin.,and need a Tocco hardened shaft.

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Re: Square Four MkI restoration complete - almost....

Postby Gui.dorey » Thu May 16, 2019 10:35 pm

The investigation went further and here are the results.

Lack of oil:
I rechecked all the the oil passages and they are clear. Used an oil hand pump and just pumped oil into the passage that feeds the rear bush and clear oil came straight out of the holes on the plain bearing. By covering one hole with my finger, oil then flowed out of the holes on the front bearing. So all the passages are clear as well as the grooves on the outside of the bearings. That means the oil supply was there. The only thing that maybe was not ideal are the positioning of the holes. According to one of my mates who is an engine designer and also restores his own classic cars, the ideal positioning of the holes for this type of bush supporting a high load shaft, and the main load being straight up and down as the pistons fire, would be at 1 & 7 o'clock or 11 & 5. Being aligned with the oil passages in the crankcase, the oil flow will go mainly straight to the bearing through the first hole, and maybe not have enough back pressure to flow around the groove sufficiently to the second hole and much less to the second bearing on the front crank. As I had my holes aligned, the front plain bearing would get much less oil than the rear one, and even less out of its second hole which was positioned at 3 o'clock. However he still thinks there should have been enough lubrication even if not the maximum one could get out of the system.


Crankshaft clearance:
The seized bush shows rubbing/friction marks on both inside and outside edges. Inside the crank was pushing against it, and outside the thrust washer. Compared to the rear bearing, which is nice and yellow, these edges of the front bush are white and show clear signs of wear. Friction marks are also to be found on the crank shoulder and on the inner side of the thrust washer. Looking at the damage to the white metal on the bearing surface, it is only damaged and broken away in the first few mm going in from the edges. the centre part is fine and likely didn't seize. So it seems to be that the friction against the edges was so much, that it developed enough heat to melt the babbit in the area just in from the edges. The bush was squeezed in between the outside thrust washer and the crank shoulder on the inside. So I had absolutely no end play on the front shaft! I know on the front crank I had almost no play and didn't add any shims.

The big question is why, and what did I do wrong during assembly. I read and re-read everything on how to set the end play, but probably didn't do it right or misunderstood the whole thing, so here my flow of new questions :) Please confirm or correct the following:

The axial movement of the cranks is controlled or limited thus:
1. towards the drive side the movement is limited by the roller bearing and the bearing itself by its retaining circlip.
2. towards the timing side the crank would move until the crank shoulder would hit the edge of the plain bearing, which should not happen and a certain clearance is needed.
3. the correct assembly on the outside timing side is - the thick thrust washer, then the necessary shims to set the proper run-out, then the nut. For the rear crank the half-time sprocket comes between the shims and the nut.
4. The shims can only reduce the run-out, not increase it, since adding shims just causes the crank to be pulled out when tightening the nut.

On my engine, there seems to be almost no run-out or end play on the cranks, and I didn't use any shims. So much so that when I tightened to nut on the front shaft, I just squeezed the plain bearing between the crank shoulder and the thrust washer leading to disaster.

I must be missing something or getting something backwards and completely botching things up…. :oops:
So, very hopeful one or more of you chaps spots my mistake and set me right. And then call me an idiot not worthy of touching such an engine….

Cheers,
Gui

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Re: Square Four MkI restoration complete - almost....

Postby john.whiting » Fri May 17, 2019 5:57 am

You have had a small seizure in an old motorbike....its not a big deal........but its certainly an object lesson for everyone on the value of white metal bearings.........if you had used bronze,the crankshaft would be deeply scored and heat effected......Anyhoo,its just a matter of establishing some clearance in the system........why there is none doesnt matter.........some alterations must be made to increase the clearance,and probably the easisest is to face off the bushing....Be a proper fitter,not just an assembler.

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Re: Square Four MkI restoration complete - almost....

Postby Knud.Degnbol » Fri May 17, 2019 8:50 am

You can increase the end float by placing a small diameter shim between the thrustwasher and the crank.


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