Fit an A65 oil pressure switch to an A10?

[mikeb]

I see some posts of people fitting oil pressure gauges to the A series, but has anyone fitted an A65 type oil pressure switch?
The challenge would be that the usual take off is drilled in behind the PRV and perpendicular to the PRV (see pics – not of my bike). That angle would be too close to the cases for a larger bodied pressure switch, so it would need to be drilled at a slightly rotated angle, which looks risky. being a tapered thread may help.

Anyone done this? Any thoughts?

thanks

[chaterlea25]

Hi Mike,
The pressure switches operate at 7-10 lbs sq in. so only a last ditch warning
By the time it would come on when riding along the damage would have happened 
Taper threads in alloy seems to be a recipe for disaster IMHO

Recently I took this photo of an Ariel Huntmaster crankcase (same internals as the A10)
The boss looks as though it was intended to be used for an oil pressure tapping directly from the main bearing
Its a shame BSA did not do the same

John

[mikeb]

John - there's been something stealing my oil pressure so would be good to know if it happens again, so my 'logic' is at least a little red light at 7psi would be some indication. i share your concerns about tapered threads into these cases - I've wondered about getting that area built up a bit first.

i may be over thinkng this again - just don't want another crank grind after the next 6000 miles

[chaterlea25]

Hi Mike,
I would prefer to fit a gauge than a light if you are going to the trouble of drilling into the oilway?

John

[mikeb]

that's an optionJohn, tho it sound like many folks who fit gauges get alarmed by the low pressure (when hot, idle) and take them out. And I'd have some concerns re the tube going to the gauge - another place for breakages and the oil to escape. Tho I guess there's less weight rattling around on the end of a tapered thread.
would you build up the cases a bit first, before drilling?

[Colsbeeza]

Hi Mikeb,
I fitted a pressure gauge, and I share your concern about damage. However, I had the area built up to take the drilling. (See photo). That Ariel design is much better. I have since reinforced the line a little, and I have a crash bar fitted which protects the area somewhat. But I do watch closely - can be a bit distracting but comforting.! Oil pressure is 60psig as per the spring setting on startup cold, and drops to about 40 when hot. I think an oil pressure switch would be even more exposed to a knock. If it snapped off - doesn't bare thinking about. You would have to locate it elsewhere and run a line up to it, so you might as well have a pressure gauge.
Col

[KiwiGF]

Just a thought but it must be possible to modify a std prv, or make a new one worst case, that has a drilling for a gauge? Wouldn’t that be better than drilling a crankcase?

[Greybeard]

Just a thought but it must be possible to modify a std prv, or make a new one worst case, that has a drilling for a gauge? Wouldn’t that be better than drilling a crankcase?

Or maybe a male to female extension collar for the PRV with a tapping in the side for the pressure take-off.

[Colsbeeza]

Yes that would be much better. The male bit could be threaded oversize to cater for worn threads.?
Col

[mikeb]

so Col - it looks like you drilled right through into the back of the timing bush? rather than just up in behind the PRV? is that right?
pros and cons?

EDIT - i can't quite see how you would make a PRV extension collar as it needs to return the oil to the gallery that feeds to the cams/cases. can anyone sketch their ideas?

[Greybeard]

... i can't quite see how you would make a PRV extension collar as it needs to return the oil to the gallery that feeds to the cams/cases. can anyone sketch their ideas?

Ah yes, I'd forgotten that 😒

I just found a picture of the SRM plunger/piston type PRV. Any thoughts on making an extension piece?

[berger]

i think the only way to do it off the prv is to moniter what pressure it is letting pass up to the camshaft and timing gears and as this drops it could well be telling you something is wearing -ie bronze bush or big ends . this is one i made to experiment with when i ran the engine with the passasge to the camshaft and timing gears blocked off with the rubber O ring and then without the O ring

[Colsbeeza]

Yes Mike,
I had the area built up, and hand drilled a tiny hole to pot the centre of the bush. I got it in one go luckily.
looking at GB's photo, it doesn't immediately spring to mind how to make the extension bush to take the pressure gauge/switch offtake and still allow good flow to the bigends.
No doubt the solution is simple - someone will tumble to an answer.!
Col

[chaterlea25]

Hi ALL,
Dave Madigan on Britbike made some prototype PRV's that would incorporate a pressure gauge take off
The units needed a contra flow passage to leave the oil that passed the ball valve to get back to the leak off position.. It was clever thinking and I would say an expensive part to make!!!!
The Trihards do not use the bypass oil like the BSA does , so those guys are trying to stop leakage past the first couple of threads and keep all the pressure to the big ends

I think that a little leakage past the threads on the A7 /10's is a positive as it ensures the cam trough is kept full,  especially once the oil is hot and not popping the PRV   

John

[KiwiGF]

Ok I will have a crack at a “conceptual” drawing, apologies for quality but I used my finger to draw on an ipad 

This is theoretical, I have not tried to make something. It’s based on modding std parts. someone must surely have successfully done this and I’m just throwing an idea out.

The red shows a possible oil path, the drilling to the gauze filter end would have to be tiny, 1 mm?

The difficulty would be getting the oil from that drilling, to the “outside” and to a tube leading to a gauge, I thought maybe the bolt could have a small amount machined off under the head to make a path from the drilling to under the head, without compromising the sealing surface of the bolt head too much.

An alternative design could maybe use a custom banjo fitting under the bolt head.