What is your opinion on the plastic oil pump gears?

[Snowbelt Spyder]

It would be interesting to know, though, what they do use in those engines.

The oil pump/filter assembly bolts to the front of the engine. The oil pump drive shaft is keyed directly to the front face of the camshaft. No gears. If the cam is turning, the oil pump is turning.

 

[Dasmoetorhead]

The oil pump/filter assembly bolts to the front of the engine. The oil pump drive shaft is keyed directly to the front face of the camshaft. No gears. If the cam is turning, the oil pump is turning.

That's good to know. Thanks

 

[Peter Aawen]

Not sure they could get away with a nylon gear in an aircraft motor. A bit more riding on components in that application. Rare oil pump failure is probably not so acceptable in a plane.

It would be interesting to know, though, what they do use in those engines.

Funny you should say that.... There was a time in the dim dark past where I flew Victa Air-Tourers, which were small, single engined, low winged, civilian aircraft - https://en.wikipedia.org/wiki/AESL_Airtourer and their later Aero Engine Service Ltd/Pacific Aerospace Corporation 'Military' version, AESL/PAC CT-4's, which were small, single engined, low winged military (training) aircraft - https://en.wikipedia.org/wiki/PAC_CT/4_Airtrainer - both aircraft which were basically originally built by Victa & ultimately used a fair bit for training new pilots, civilian and military...

Mind you, it'll help explain my point if you understand where Victa came from - they originally started out making outdoor garden equipment, including petrol, electric, and battery powered lawn mowers, edgers, trimmers, and chainsaws, before branching out into making aircraft, albeit eventually selling that branch of the business off: Here's some background: https://en.wikipedia.org/wiki/Victa

However, those of us who flew &/or maintained these Victa Airtourer & CT-4 things found out that there were actually quite a LOT of nylon gears, bushings, and other sundry parts in these aircraft, some of which were in 'high wear' areas; and we discovered very quickly that some of the 'nylon' parts used in these aircraft had a tendency to wear out pretty quickly... not to the point of causing aircraft to fall out of the sky without warning, but certainly such that pre-flight checks or maintenance checks often found the nylon parts were worn to an 'imminent failure' degree!

From there, it didn't take too long to work out that sourcing the appropriate 'aircraft' &/or 'mil-spec' spares to replace the worn out parts was often difficult, expensive, &/or they would take quite a while to get in, especially if you needed to get the mil-spec gear!! And that'd mean there'd often be fairly long periods of time where an otherwise serviceable aircraft would be sitting around waiting for some simple but fairly critical part like a nylon gear, a bushing, or maybe just something simple (but reasonably essential) like the trim-tab detent - but there's a very strong rumour that'll I'll neither confirm nor deny here that if you were truly stuck, you could often just duck down to your local hardware store/lawn mower shop and buy the equivalent 'lawn mower/chainsaw' part (often with the same part number, minus the aircraft/mil-spec identifiers on the end ) and use that to get the aircraft back in the air while you waited for the 'proper spec' item to (eventually) come in... Not that I would ever be party to something like that, tho...

But I can assure you from first-hand experience that you really shouldn't underestimate how many nylon parts there might be in an aircraft/aircraft engine! I strongly suspect that there's WAAAAYYY MORE than you'd ever expect!!

 

[pauly1]

While nylon is technically a plastic, it is not what is usually thought of as plastic. Nylon is very durable, wear resistant, and unaffected by most lubricants. It is typically used in many devices and machines as a lighter weight and easier to produce substitute for metal parts. People usually think of plastic as pop bottles or other small, breakable items.

You are correct, nylon is a plastic, made with fossil fuel products, but it is a very high end plastic. I would not put it in the same class as most plastic items. It has been used for years to make gears for fishing reels, and other small durable parts that take a lot of wear and stress. It is unaffected by exposure to salt water or other corrosive elements that cause problems if the parts are made of typical metals.

Plastic is plastic. What "people usually think" does not change the fact that it is a type of plastic. Nylon, technically polyamide, is a family of plastics. PA 6/6 is a very common type, often modified to enhance performance. For example, fiberglass is often added to increase tensile strength, shear strength and flex modulus; often, if the part is large enough, one can find a "PA 6/6 GFR" molded into the part for identification. It is formed via condensation polymerization: it's Achille's heel is that it has a high affinity for reabsorbing water, degrading strength but improving impact performance.

Of interest may be that the gear likely shares a basic chemistry as common fishing line.

Another plastic, polyoximethylene, POM or acetal, for short, has most of the properties of PA 6/6. It is ofter used as a lower cost substitute. It doesn't have the moisture re-absorption issue, but has a melt temperature of about 100 F lower that PA 6/6.

Indeed, nylon does have the properties you listed. It the industry it is considered a low-end, engineering grade of polymer, separating it, and host of other plastics, from your "people usually think" definition. While it is most often a petroleum-based derivative, it can be synthesized from other organic sources.

Performance and price are closely linked. Lower performing materials, like polystyrene (PS), polypropylene (PP), polyvinylchloride (PVC) and polyethylene (PE), are commonly used for "small, breakable items", packaging (shopping bags), large painter's drop cloths, and see-though packaging (bubble pack). They are in the $0.50/lb range. The lowly bottle steps up the performance curve made from largely polyethyleneterethalate (PET); the material is responsible for not only holding the liquid but also the carbonation in the case of a soft drink.
Polycarbonate (PC) in football helmets and polyamide (PA or nylon) are in the $2 - $3/lb range. At the higher end is polyamide-imide (PAI), which is the range of $40-$60/lb. With the myriad of choice available, it is incumbent on the engineer and design team will select the best plastic (cost and performance) for their needs.

"People usually think..." of plastics definition can be tied to mainstream news, and social media, reporting on the "horrors" of plastics, citing packaging and 6-pack rings around a birds neck. And while these are tragic situations, there are many applications of PA and even higher performing plastics for which there are no alternatives.

Respectfully, plastic is plastic. In this case, a cost-effective, mid-tier performing plastic that has the right properties

 

[WRCLVR]

Re Ford using nylon camshaft gears - in most of their 1970's V6's 2.8 L engines applicable globally, they were nylon teeth but the crank gear was steel. Yes, they broke at unexpected times, but the engines were (are) non interference, so there's no issues with that other than the rather not so nice replacing procedure. IIRC, most of the replacement gears were either steel or aluminum.