ET: Engine (Twin) Oil Pump and Oiling Sytem Modifications

[Tnecniv Edipar]

I've always wondered why not just Vincent but most of the British manufacturers used such primitive and poor lubrication systems, like reciprocating plunger pumps and recip and oscillating pilgrim pumps, like on the Vincent? When Honda introduced their ground breaking 50cc cub, even that got a trochoidal lobe pump that had serious and constant delivery at good pressure!!! Ok, it was designed later than such as Vincents, but even humble, simple and crude British family cars of the same era as Vincent and other bikes, got proper lubrication systems. Even simple gear pumps would have been a much better solution.
So why did Irving go for that oil pump rather than a gear or trochoidal pump, when the rest of the machine was so advanced I wonder?

 

[greg brillus]

Roller bearing cranks don't need much oil delivery (not so for cams/followers though) and the pre war bikes wet sump........Norton's, BSA etc........that was probably their thinking.

 

[Tnecniv Edipar]

Roller bearing cranks don't need much oil delivery (not so for cams/followers though) and the pre war bikes wet sump........Norton's, BSA etc........that was probably their thinking.

Well roller bearings don't require pressure but high flow is a good thing, and this is where the pilgrim type pump falls down. High flow is also good for cooling. Also, the British vertical twins from Triumph, BSA and Norton had plain bearing cranks, with recip pumps!! I think AMC had 2 gear pumps, one for feed, one for scavenge, as they were a bit up market, although percieved as dull by the boy racer types! Velocette of course used gear pumps, even with roller and ball bearing bottom ends, but spoilt it a bit by making the attachment an interference fit, not great for overhaul or maintenance! Why not just bolt it on with an O ring seal?!

 

[Robert Watson]

Roller bearings, (crank and rods) are indeed different from Plain bearings and rubbing surfaces (cams and followers) and indeed have different oil supply requirements. No oil pressure to speak of in a roller bearing crank is considerably different from no oil pressure in a plain shell bearing big and or crank bearing.

High flow for roller bearings is NOT a good thing. We had a customer in industry running some very large roller bearings (probably around a 5 inch shaft at 1000 RPM or so). On an in house rebuild they decided that they would "improve" the oiling system to these bearings and installed a pretty high volume oil pump to lubricate these bearings. Things go quite sideways quite suddenly if one of these bearings fails so they have vibration and temperature sensors on them to prevent major destruction. On this fresh startup all was good for a short while until the unit kept shutting down due to overheated bearings. After berating some suppliers the bearing guys go out to inspect and ask about the new oiling system. very proudly the millwrights explain how they built it and how great it is. They get told in no uncertain terms to dismantle it and reinstall the original pump system, and not until upper management gets involved do they comply.

Too much oil in a roller bearing turns it into an oil pump with a restricted exit, it gets very hot.

Be careful what you do

 

[Tnecniv Edipar]

Well it works for Ducati Bevel twins, and singles, also Velo's. The gear pumps on Ducati's push out a fair flow, there is a pressure relief valve for cold starts though. Velo's don't have quite the same flow as the Ducati, but it's obviously constant and better than a recip pump. I wasn't advocating high flow AND high pressure for roller bearing crank engines, but the dribble produced by Vincent pumps is marginal, IMHO.
Although I expect there will be many that disagree and will cite examples of engines having covered many 10's of thousands of miles with the stock arrangement.

 

[oexing]

With a high flow oil pump you get the choice of directing oil to some more places like cams, cylinder bores and the rest. For the crank and big end bearings calibrated jets can limit oil flow to useful percentages when having roller bearings there. Indeed, roller bearings do not need high oil flows , but piston cooling by oil jets would be desirable.

Vic

 

[BigEd]

The Honda C100 step-through scooter, first made in 1958 was made in huge numbers. It had no oil pump but it did have a small extension at the bottom of the connecting rod that dipped into the sump and threw a bit of oil around. These 50cc machines did thousands and thousands of miles. The 1000cc Vincent engine also did thousands of miles without major problems. There is no doubt that most designs can be improved but the original design of both these machines worked well for their intended purpose.

 

[Chris Launders]

Well it works for Ducati Bevel twins, and singles, also Velo's. The gear pumps on Ducati's push out a fair flow, there is a pressure relief valve for cold starts though. Velo's don't have quite the same flow as the Ducati, but it's obviously constant and better than a recip pump. I wasn't advocating high flow AND high pressure for roller bearing crank engines, but the dribble produced by Vincent pumps is marginal, IMHO.
Although I expect there will be many that disagree and will cite examples of engines having covered many 10's of thousands of miles with the stock arrangement.

The Ducati bevel drive twins oil supply is divided into 4, as well as the crank it also feeds directly to both cams and 1/4 goes straight through the oil filter back to the sump.

 

[Tnecniv Edipar]

Yeah, I fitted an oil cooler to my 900SS in 1983 when I rebuilt it as an NCR replica after dropping it returning from the Bol 'Dor. I had to block off the head oil feeds of the original layout by fitting a solid dowel to replace the hollow original, Then with a special oil filter housing adaptor that had a feed port in the top, a line was fed to one side of the cooler, a line from the other side went to a T piece, a line from each side of which fed to the cam bearing block's after they had been faced, drilled and tapped to take a banjo bolt in the centre. Worked really well even though it was only receiving 25% of the total flow. Wish I'd never sold that bike, sigh!

 

[Chris Launders]

Yeah, I fitted an oil cooler to my 900SS in 1983 when I rebuilt it as an NCR replica after dropping it returning from the Bol 'Dor. I had to block off the head oil feeds of the original layout by fitting a solid dowel to replace the hollow original, Then with a special oil filter housing adaptor that had a feed port in the top, a line was fed to one side of the cooler, a line from the other side went to a T piece, a line from each side of which fed to the cam bearing block's after they had been faced, drilled and tapped to take a banjo bolt in the centre. Worked really well even though it was only receiving 25% of the total flow. Wish I'd never sold that bike, sigh!

We modified a mate's back in the 90s, blocked off the head and crank feed, all the oil comes out through the filter housing top, then through an external filter, cooler and then divides into three, one to each head and one to the drive side of the crank.