Sharing data on failure points

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Sharing data on failure points

Postby pbove » Tue May 01, 2018 9:37 am

We seem to have quite a lot of attrition at Brands Hatch, some due to technical issues, some due to htting the barriers (guitly as charged).

I think it might be helpful for us to share the reasons for failure so that we can all learn from the issues we suffer and improve the general reliability of the cars which will be to all our benefit. For example, I felt quite guilty when someone suffered their oil filter coming loose on track last year and all I could say was, yes, that's why we use a jubilee clip and lockwire to retain them. Even now, I'm guessing that some people have not heard about this trick.

So, please share your technical issues with us so that we can all try to avoid suffering the same fate. My tip ........ try to avoid too much rear brake bias when braking heavily at an unexpected part of the track...... :(
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Re: Sharing data on failure points

Postby tdriscoll » Tue May 01, 2018 1:48 pm

This is a really good idea.

I've had a few stops on track for silly reasons - mostly boiling down to one thing: Do your spanner checks thoroughly!

Throttle cables, screws in carb butterflies and even the nut holding the gearbox output flange can, will (and have) come undone and fall off, resulting in 3 retirements and 1 non-start.

Also, lockwire on the 'teapot' lid on your carb. Mine vanished at Silverstone last year; didn't hurt my performance, but could have caused me or someone else mischief.


***UPDATE***
A good example! At Brands, I got stuck in 3rd during race 1. This was because the circlip (from a generic box) was 1 size too small, and was wrenched out of the circlip groove, and the selector fork followed it out of the 'box. Correct size (23mm) circlip and a couple of shim washers later, and that's solved.

However. gearbox output flange seems a bit movable...propshaft off... sh*t. The aforementioned nut is about 4mm down the thread! Enter stage right a special tool for doing this nut back up without forcing the gearbox between gears, which just feels like a nasty thing to do. This was Rod Hill's suggestion (he has something similar), some long bolts through a bit of steel bar, to hold the flange through the bolt holes.

WP_20180510_003.jpg
Special tool for doing up gearbox
WP_20180510_003.jpg (221.11 KiB) Viewed 722 times
Last edited by tdriscoll on Thu May 10, 2018 8:14 pm, edited 1 time in total.
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Re: Sharing data on failure points

Postby Martin Kemp » Tue May 01, 2018 6:22 pm

Radiator Cap
I drill a hole on the edge of the radiator cap and ty-rap it to the overflow pipe because I have the caps come loose before now.

Crankshaft cambelt pulley
If you don't know now, you will find out pretty soon that the standard key on the crankshaft cambelt pulley is not strong enough and when it gives up you get a lot of bent valves. Drill out the keyway through the small hole in the front, 6mm or 1/4 inch, and grind a matching rounded slot in the crankshaft with a Dremel grinder and tungsten burr - it doesn't need to be perfect but it does not want to be loose. You can do it without stripping the engine. Add some Loctite High Strength Retainer and tap in the correct 6mm or 1/4 " rod. Dress the end flush and bolt it up to the specified torque.

Alternatively you can make a square keyway in the pulley and fit a square key but if you haven't got the tools then you would have to pay someone to do it for you and a round key is perfectly good.

Something to beware of is that some pulleys and crankshaft ends have a slightly larger diameter than normal so if you swap pulleys and crankshafts around they may not fit properly (of course, why would you make them all the same size).

Fuel lines
Last thought of the day, as I found at Brands, flushing 2 litres of fuel through a new fuel pipe is not enough to stop the filter from clogging up in your first race of the season, but it is enough to stop you realising that was the problem.

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Re: Sharing data on failure points

Postby pbove » Wed May 02, 2018 9:19 am

One of Mr Harvey's mantras was that anything that can move should be tywrapped to stop it moving..... fuel lines, brake lines, water pipes, wiring, it all needs to be secured to avoid the movement creating a failure somewhere.

I've mentioned the jubilee clip/lockwire trick to stop oil filters coming unscrewed.

"Push on" oil hoses need to be secured with jubilee clips even if they claim that they don't.... ask Huw!

Keep anything that melts away from anything hot - obvious really, but easily overlooked.

Measure the depth of the cylinder block bolt holes before fitting the head to make sure that they are not full of crud that will stop the head bolts from torquing up properly.

If you're running a Polestar, check the trigger disk regularly, they are subject to cracking and, ultimately, failure.

Oh and, a couple of Falcons have experienced oil caps coming out mid race in an, often successful, bid for freedom. It's worth having some kind of retainer.
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Re: Sharing data on failure points

Postby Martin Kemp » Wed May 02, 2018 1:14 pm

Do up your helmet strap as soon as you put your helmet on - always - even if you are just driving to scrutineering. It needs to be an invariable habit.

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Re: Sharing data on failure points

Postby suebmick » Fri May 04, 2018 7:15 am

We do a full nut & bolt & leak check at home before a race.

But I have always found that having checked all wheel nuts before leaving home, just one nut on one of the rears needs a slight re-tighten at the end of the journey to a meeting. No idea why it's always that one, but it is. The car goes through much more bouncing & rocking & rolling on the journey down the motorway than it ever does on track

As the doctors say, always check your nuts, boys!
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Re: Sharing data on failure points

Postby Conway » Sun May 06, 2018 9:52 am

Great thread everyone and interesting reading. From my recent experience... CORE PLUGS!

Replacing core plugs, at least the large tin lid type at either end of the block, makes them vulnerable to blowing out. Asking around I discover this is well known - thanks to those who offered advice and to Mick who even offered a core plug!

The solution is to add a retainer of some sort - a bar across, or a cap screw and penny washer overlapping the edge of the plug.

Soo fed up with mopping up coolant!
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Re: Sharing data on failure points

Postby pbove » Sun May 06, 2018 11:09 am

If you’re fed up with coolant then try gravel!! :(
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Re: Sharing data on failure points

Postby Conway » Tue Jun 12, 2018 8:32 pm

Flywheel bolts and crankshaft timing pulley

Just copying these pearls of wisdom over from a different thread because it's really relevant to this one too.

Good advice from Martin Kemp following my DNF at Rockingham. The engine failure was caused by the standard 8.8 grade flywheel bolts shearing (c. 5kg flywheel) at high revs, the timing pulley at the front end of the crankshaft simultaneously shearing its integral locating key, the consequent lack of synchronisation allowing the valves to clash with the pistons. I plan to upgrade to 10.9 or 12.9 bolts for the rebuild but Martin also says...

The new crankshaft pulley will also fail unless you make a more robust keyway. I do it by drilling a 6mm or 1/4" hole though the dimple in the front of the pulley through the keyway thus making a semi-circular keyway slot in the pulley. Then I use a dremel to turn the keyway slot in the crankshaft into a tightly fitting matching groove and reassemble with a dowel and some Loctite high strength retainer.

This method doesn't require any fancy machinery and we haven't had a failure yet - although one did develop some play during the Birkett last year - at least it was just a power loss and not a power unit loss.

I also use High Strength Retainer on the flywheel bolts. When you need to get it undone heat from a blow torch will destroy the Loctite.
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Re: Sharing data on failure points

Postby Martin Kemp » Wed Jun 13, 2018 6:23 pm

We fitted new fuel lines over the winter and flushed them through. Then we had 2 DNFs at Brands because some sort of gooey mess from the fuel lines clogged the carburettor inlet filter. So when you fit new fuel lines leave them with fuel in for a week and then flush them again before you go racing,

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