Lucas Mechanical PI System Model

[Vixen]

I am still working on the design of the body. One end will have the cam/wedge to control the shuttle position, the other some form of drive coupling (very small Oldham style?). Both ends will have to have a return line for fuel that leaks past the shuttle or rotor. I will also need to select a suitable way to retain the fixed shuttle stop. For the finished item some form of Loctite would work, but in the experimental phase it needs to be a removable mechanical fixing. I am looking at either a very small grubscrew in the rotor, maybe M1.6 x 2, or a M1.4 screw from the coupling end.

Roger,
"When in Rome do, as the Romans do".  When in Switzerland, "make it like a Swiss watch".

Hope that helps. 

Mike

[Roger B]

I turned a pair of nuts for the rotor from 8mm brass hex, one short one for the control end and a long one for the drive coupling. As anticipated I had to cut a 0.5mm run out groove at the end of the threads so the nuts seated on the rotor. I could then assemble the rotor and sleeve using shim washers to centralise the ports.

I will need an electric fuel feed pump for the trials, potentially working up to the prototypical 7 bar. The Modelcraft pump I have been using struggles to reach 2 bar so I wondered if I could modify one, possibly with some reduction gearing.  The gears are definitely designed for flow rather than pressure and I can’t see a way to remove the drive piece from the motor without damaging anything. It seems firmly pressed or bonded in place. I will make my own pump using 24T MOD 0.5 brass gears and a Portescap 28mm motor from the bits box.

The body is a piece of 20mm square aluminium, drilled 11.5mm and reamed 12mm. There are M5x0.5 threaded holes for the two delivery valves and the fuel inlet. I then cut a 1.5 x 0.7mm groove for the O ring that will seal the sleeve to the body. At the other end the O ring groove is in the sleeve to allow it to be assembled without shredding the O ring on the ports.

[Roger B]

Next up was the first attempt at the three metering components. These are all from 2mm silver steel. For this first trial I am not hardening and lapping them.

The fixed stop and the control stop were turned down to 1.5mm for the appropriate lengths and the end of the fixed stop was taped M1.4 for a fixing screw.

[55fairlane]

Watching this with great interest,  I spent a lot of time at Kinsler fuel injection (Troy Michigan), I raced hemi powered cars, and they were motivated by Hilborn mechanical fuel injection, so I needed to learn to meter alcohol.  We were drag racing,  the Cuda made a mere 900hp (big big horsepower in its day) to 3000 plus on nitro methane  for the digger....mechanical fuel injection will build rpm faster then super charger, and doesn't rob near the power off the engine.   

Turned several carburetor intake manifold to mechanical fuel injection manifold no one made a great manifold for small Fords......

...do you need a vapor separator catch can ? Or can you you simply return by passed fuel straight back to the tank? What are you doing for a high speed by-pass ? Same with low speed by-pass? Gonna use the high speed by-pass as a rev limiter?  How are you calculating the leanth of the air horn (bell on top of the injection stack)?

I'm gonna have to dig out all my books and information to brush up on Lucas metering............if memory serves me right in late 70's or early 80's USAC racing , you ran carburetors and alcohol.......someone showed up with a Ford , Lucas metering on gasoline,  and wooped the track! USAC outlawed gasoline and mechanical fuel injection.....

Loving this build!

[Vixen]

Hello Roger.

Still following closely.   

Mike

[steamer]

Hello Roger.

Still following closely.   

Mike

Absolutely!!!

[Roger B]

Thank you all for your support 

The next challenge is a miniature Oldham coupling. The first section screws onto the end of the rotor, butting up to it to help keep the alignment. The small gap confirms this is the case. I used a short piece of 8 mm brass hex with an M4 x 0.5 mm thread (left over from making the nuts) as a holder to drill through 1.5 mm with a 2 mm counterbore for the holding screw for the fixed stop.  The holder was then moved to the Proxxon mill to cut the 2mm slot.

[Roger B]

I turned an offcut of Delrin down to 6mm for the coupling element. This was then drilled through 1.4 mm to allow the element to be held for the second operation. For this step I needed an M1.4 screw with a 2mm diameter head. A commercial socket head screw was held in a 3 mm brass adaptor and carefully turned down to 2 mm diameter. This seemed to work and left sufficient material around the hexagon.

The Delrin blank was set up in the Proxxon RT and the tongue was milled, turning through 180° at each step. The 3 mm length was then parted off.

[Roger B]

The coupling piece was put back in the holder and set at 90° in the RT. It was then removed so that the coupling element could be fixed to it with the reduced M1.4 screw. This assembly was put back in the holder and the second tongue was milled. The finished coupling element was quite difficult to photograph.

The next piece was the drive part of the coupling. This was made from 6mm silver steel turned down to 4mm for the drive shaft. The 2mm slot was cut once again with the Proxxon mill followed by a quick trial assembly.

[Roger B]

Watching this with great interest,  I spent a lot of time at Kinsler fuel injection (Troy Michigan), I raced hemi powered cars, and they were motivated by Hilborn mechanical fuel injection, so I needed to learn to meter alcohol.  We were drag racing,  the Cuda made a mere 900hp (big big horsepower in its day) to 3000 plus on nitro methane  for the digger....mechanical fuel injection will build rpm faster then super charger, and doesn't rob near the power off the engine.   

Turned several carburetor intake manifold to mechanical fuel injection manifold no one made a great manifold for small Fords......

...do you need a vapor separator catch can ? Or can you you simply return by passed fuel straight back to the tank? What are you doing for a high speed by-pass ? Same with low speed by-pass? Gonna use the high speed by-pass as a rev limiter?  How are you calculating the leanth of the air horn (bell on top of the injection stack)?

I'm gonna have to dig out all my books and information to brush up on Lucas metering............if memory serves me right in late 70's or early 80's USAC racing , you ran carburetors and alcohol.......someone showed up with a Ford , Lucas metering on gasoline,  and wooped the track! USAC outlawed gasoline and mechanical fuel injection.....

Loving this build!

Thank you for your interest 

As the Lucas system uses timed injection pulses rather than continuous flow a lot of the complications of the Hilborn system goes away. Engine speed is automatically compensated for by injecting on each induction stroke.

Load compensation is from the throttle position on competition engines and the manifold vacuum on ‘normal’ engines.

[55fairlane]

 Kinsler.com lots of neat mechanical fuel injection

I'm guessing a rotary valve is used to control each pulse of fuel? Is that valve driven off the crank? Belt drive?

I need to look into Lucas much closer

[Roger B]

For various reasons I decided to modify the body design so that each end plate has a spigot to fit into the body and hold it central.

This requires a new, longer, body. The 12mm diameter 1mm long spigots were turned on the end plates and they were parted off from the stock. The spigot could then be held in a 12mm spring collet to allow the other side to be faced. It all seems to fit together ok.

A few weeks ago I ordered some gears for the fuel pressure pump from Ali Express. I received the expected 6, very long, pinions and a bag with grub screws and a hex key. These  are 24T MOD 0.5 with a usable length up to nearly 12mm. I hope the tooth profile is good enough for up to 7 bar with petrol.

[Roger B]

So continuing with the body. The inlet and outlet holes were drilled and tapped M5x0.5 and 2mm fixing holes were drilled in the end covers. These were then spotted through to the body and tapped M2. 1.2mm drain holes were drilled in each end cover to release any fuel that leaks past the metering system.

The control end cover required some thought. For the initial tests a simple screw adjuster is required but this must be convertible to a quick acting lever for engine trials. It is also important that the hole in the end cover is less than 2mm diameter to minimise the chance of the adjuster coming loose and the metering shuttle shooting out followed by a jet of fuel at 7 bar. I finally decided to press in a 4mm diameter bronze bush with a 1.5mm hole for the adjusting pin and an M3 thread for adjusting. Even if it becomes unscrewed the shuttle will only reach a maximum stroke of 2.5mm. For the final design I can press the bush back out and replace it with something else.

The drive end is drilled and reamed 6mm for a 4 mm bore bronze bush. Unfortunately the cover pulled out of the spring collet as the drill broke through. I was able to finish this off in the 4 jaw SC chuck as the concentricity requirement are not great.

For the next version I will develop an alternative machining sequence for the covers.

[Admiral_dk]

Great to see more progress on this very ambitious Project  + good to hear that the latest mishap was easy to cure 

I haven't chimed in earlier this year, as I had a minor work related accident on a eBike January 2nd. 
Didn't give it much thought at the time - only bruised skin on the left knee + it became swollen ....
Ten days later I was admitted to the local Hospital with a serious Infection for 76 hours + several weeks of laying on my back when I got back home .....
I did enjoy reading MEM and this thread very much - but didn't feel up to replying at the time ....

Best wishes

Per   

[steamer]

Sorry to hear that Per.....I know I dont bounce like I used to.

looking good roger!   following along