OV9

Our direct competitors suffered total catastrophic engine failure yesterday after 3 laps. Looking at probably £5k rebuild. Something punched a hole in the side of the block very similar to our engine detonation last year. Annoyingly the engine had just come back from the race builders after a refresh. No warranty given with race engines however.

“No warranty” is a bit alarming - he must be suspecting that something wasn’t quite bolted up as it should have been?

He is ridiculously quick though, so a lack of engine might give you a bit of a boost.

Oof, that's got to fucking hurt.

mik wrote: Mon Feb 17, 2020 3:52 pm “No warranty” is a bit alarming - he must be suspecting that something wasn’t quite bolted up as it should have been?

He is ridiculously quick though, so a lack of engine might give you a bit of a boost.

We suspect a snapped crank was the issue.

I get the whole “no warranty” thing but a snapped crank on its first time out, on a practice day is some serious bullshit. I’m suspect a conversation will be had about shared costs at the very least.

NotoriousREV wrote: Mon Feb 17, 2020 4:47 pm I get the whole “no warranty” thing but a snapped crank on its first time out, on a practice day is some serious bullshit. I’m suspect a conversation will be had about shared costs at the very least.

Crank wasn’t replaced at the refresh. Has done two seasons. The engine refresh is just a strip down and visual inspection. They use the same engine builder as us and most of the formula ford community. They are well renowned as the best in the business. The professional teams we race against all use them. Unfortunately the cranks that are supplied are sometimes of variable quality. Neil can explain the process better as he’s been to the factory and seen what they do.

You can only really do a few checks on a crank....

Check dimensions
Hardness test
Crack check with some kind of non destructive test. We use dye penetrant, some use magnetic.

The only way we have had cracks found in an otherwise visually ok crank is by destructive testing at the manufacturer.

Possibly harmonics, dampers play a really important part in a healthy crank. You want the peaks of the harmonica to collide in front of or behind the crank, never over a journal.

Dave!

Not sure if Scott knows something I don't, but I think this one was a con rod bolt failure (no.1 suspect in my blow up too). Crank looking intact but badly scored from what I saw through the potato-sized hole in the block.

Cranks are a bit of an issue at the moment. Original cast cranks are, and always have been, a bit shit. Once upon a time that was everybody's only choice, and the chances of an engine making it to the end of a season wasn't much better than 50/50. Then the rules changed and they allowed the use of forged steel ones. To begin with this was great - I had one in the old engine for 5 years with no problems. But then they changed in 2017/2018 and loads of people started having problems - my friend Ross broke 2 in 3 races, and the resultant bills basically ended his racing. Unfortunately the one authorised manufacturer absolutely denies there is any problem, or even that anything changed (even though the old and new cranks are obviously different in both colour and finish).

When I had mine rebuilt (if you can call a pretty-much ground-up build a "rebuild"), I was lucky that one of the big teams in England had just custom ordered a batch of billet ones and there were 2 left. Not cheap at £2.5k (compared to £1k for a forged steel one), but better than being in constant fear of it going pop at any moment.

Oh and re. the warranty thing - I think it just went down to the builders for a visual inspection rather than an actual rebuild. I don't know how far they stripped it down, but I know it was a tight budget job. I also know it was run and tested on the dyno, because it was on there when I went down to pick mine up.

Its never a rod bolt failure although thats what people love putting it down to.

The bolt will have failed as a result of the rod welding itself to the crank more than likely. It'll be oil starvation or they didn't tighten the rod bolts up. For example, honda k20 rod bolts are 22lb ft +90 degrees. If you forget to do the 90 degrees they run for about half an hour before the bolts fall out (not that i've ever done this I hasten to add).

The cranks snapping will more than likely be down to balancing.

dan wrote: Wed Feb 19, 2020 7:53 pm Its never a rod bolt failure although thats what people love putting it down to.

The bolt will have failed as a result of the rod welding itself to the crank more than likely. It'll be oil starvation or they didn't tighten the rod bolts up. For example, honda k20 rod bolts are 22lb ft +90 degrees. If you forget to do the 90 degrees they run for about half an hour before the bolts fall out (not that i've ever done this I hasten to add).

The cranks snapping will more than likely be down to balancing.

We only ever had rod bolt failures when we moved to a tightening torque from degree method. With a torque you are not taking into account the stretch so we had to tighten and then release 3 times before the final torque when using new studs. Once they were used once we only have to do it once.
Before that it was a torque (to know the bolt or nut is fully seated) and then degrees. This creates the stretch as you know the thread pitch angle so that 90 degrees = so much stretch.
On the really old stuff we actually measure the free length of the bolt and then keep tightening till we have the required stretch.

Then you have the lubricant, some are coated bolts or studs, some need oil on the threads or faces of the nuts, some need molykote or other greases etc to prevent fretting.

We had a problem with fretting which was then causing cracks in the big end. We simply swapped from engine oil to molykote and the problem went away.

When you go near the limits of any fastening it’s amazing what tiny things can affect it.

It’s all quite interesting.

Dave!

I see the begging bowl is out for said racer, meh, you know the score when you start racing

You talking about his late breaking thing?

Do we have an approved list of ways to raise money for racing?

Yes.

mik wrote: Tue Feb 25, 2020 2:00 pm You talking about his late breaking thing?

Yep

Eh, I mean if people want to support him in doing something he enjoys by having a bit of raffle based fun...?