In order to diagnose the piston failure, we would need to see detailed photos of the fracture site. If there are a series of 'beach marks' at one end of the fracture, then it would be a fatigue failur

0.2% proof stress is the stress at which the material exhibits 0.2% strain, or permanent stretch. This is the value typically published, simply because it is very difficult to define the point at whic

In the event that a bolt yields due to thermal expansion of the cases, it will only stretch until the load is reduced to 100% of yield stress. Therefore, when the engine cools, preload will fall to ar

Bacteria in fuel with ethanol is a problem. I don't know whether the issue translates to alcoholic drinks, but I don't drink, so personally it doesn't worry me. https://www.abfad.co.uk/editorial/battl

If testing for ethanol resistance, I would use a mix of ethanol and water. Much of the issue with ethanol is related to it's absorption of water and the bacteria which grow in the mix.

The Norton part won't be made of any special rubber, being a 1920s design. A lot of the modern pattern rubber parts are made from poor quality materials and don't last long. I wouldn't be confident pu

I can recommend Bunting Magnetics, I have been using them for years at work. They are always very helpful with technical advice and their products are of excellent and consistent quality. Usual discla

John, I have some experience with starter gears. If you are to continue using the noisy starter assembly, I suggest you keep a close eye on the condition of the teeth on the flywheel. A poorly engagin

I would think that removing and replacing a bolt does no more damage than re-torquing. If any damage were to be done, it will be at the peak torque, which occurs whether the bolt is removed or not. If

We have a Stearman at my field too. Wonderful sound!

I had similar comments about my Jab, subjectively quieter than the Rotax 912 and Lycoming engines. I can understand it being quieter than the Rotax engines, which are geared and run at higher rpm, but

Indeed so Ron. Buyer beware!

It is worth noting that the strengths indicated by bolt grades are minimums, and that there are a lot of very dodgy manufacturers who will mark bolts as whatever they want to sell, regardless of prope

The 'grades' referred to are the ultimate strengths and yield percentage for the fastener, whether it be metric or Imperial. A 12.9 grade bolt had an ultimate strength of 1200 MPa and will yield at 90

Re. Being pulled off the forum: I run a couple of groups on groups.io. Every now and then, I get a notification that a member has been 'evicted' because they have marked a message from the forum as sp

Agree with all your conclusions Bob. If there are resonance issues in the engine, flexing of the through bolts is not one of them. If I remember correctly, bolt failure was observed to be most prevale

All good guesses for natural frequencies, but there is no excitation at those frequencies. The excitation can only come from something which is generating vibration, rather than something which resona

Sorry, reasoning, not training. Predictive text issue!

What is the training behind the 6khz engine frequency figure? I would have expected perhaps 2 firing events power rev at 3000 rpm = 100hz. Generally, I would aim to get the natural frequency of the pa

Re. Hard vs soft washers. A hard washer with a flat on one side will tend to concentrate load at the cut edge, as the area of the washer is offset from the axis of the bolt. A thick, soft washer will