Building a Redwing

[Jasonb]

They are still not easy things to make, machining the tapered seat down in the depths of the carb and making sure the fuel hole ends up in the right place tests the old grey matter. There is probably something about machining them in my Galloway and Gade threads and I think there was quite a detailed one about these mixers on HMEM

[Admiral_dk]

You are welcome Colin. If anyone else has a senior moment- you can PM me or any of the Mods and any of us can recover the missing thread/post 

I wish .... I've been having 'Senior Moments' all my Life - the difference is that the Frequency keeps on increasing as my age do 

So even though I'm very Happy about our wonderful Mods - I can't see any of you help with the Majority of them 

Per     

ps    I too look forward to see your engine Run Colin 

[Laurentic]

Hear hear Per _know exactly where you are at!

Chris   

[Twizseven]

Currently making the Lunkenheimer fuel mixer. The plans call for 6-48 thread for the fuel needle valve. I do not have this tap/die and would prefer not to buy for a one off. What thread would you suggest that is fine enough to give fine movement.
Many thanks
Colin

[Jasonb]

5BA would probably be the simple one to go for as most ME's in the UK have that, a few thou smaller but at 43tpi quite fine. Could even go down to M3 which works out at 51tpi as I doubt you have M3.5

Attached my conversion chart for when I'm working on American kits.

[Twizseven]

Jason,
Thank you for that spreadsheet - very useful.

I opted for 5BA.

The body has chucking spigot and the top 1/2" thread done so far.  Ended up using 1/2" x26 BSB rather than the 1/2" x 24 UNF as did not have this tap/die.

Most of the little bits done, fuel inlet, orifice cap, inlet tube, fuel needle valve assembly and the valve.  Valve just needs cross-hole drilling and the spring retainer making.

Just need a day to concentrate on the drilling/tapping of the main body and the awkward fuel drillings.

I have a spare cast iron outer exhaust dome and I think I may use this to make air filter/choke assembly.

Colin

[Twizseven]

Now moved onto the cylinder head.  Cylinder Head casting into four jaw chuck and centered up, centre boss turned to diameter and depth.
 
Head then moved over to Rotary Table on mill, centered up on the boss and then the DRO’s circle feature used to drill the head stud holes, the valve guides and the decompressor hole.
 
The guides were then reamed to size prior to cutting the valve seats.  I had purchased a nice new Osborne cobalt 90 degree countersink cutter to do the valve seats.  I used a piece of emery underneath the cutter to prevent any chatter and this worked perfectly.
 
 
When I purchased the casting I was given a pair of valves.  The first one lapped in okay but the second had a good wobble.  I went down to my mate with his Hardinge lathe and we used his expertese to get it straight.
The spent some time lapping the valves in.  Various ways had been suggested to do this, but inthe end I opted for old fashioned wooden stick and sucker.  Well not actually a sucker but used a hot glue gun to fix the wooden stick to the valve head.  It worked reasonably but came unstuck every so often.  Next time I do anything like this I will put a small screwdriver slot in top of valve.  Based on all experience grinding valves in on cars I preferred to used a back and forward rotary movement and push down on the valve.
 
The head was then assembled on engine to see what it looked like.
 
 
In between the two photos above I changed the tappet adjustment screw to something looking a bit more appropriate, machined the pulley and the exhaust, but have no photos of these operations.

[Twizseven]

Now moved onto the fuel mixer.  This is a Lunkenheimer mixer and I searched around for any build help I could find and eventually found some instructions for machining similar mixer but from different castings.  This helped me get my machining in sequence.
I had been looking for suitable tap and die to do the thread in the top of the mixer.  This should have been a 1/2″ x 24 UNF.  I did not have one and could not find one at a suitable cost.  My mate though he might have something suitable so too the casting with me and had a look through his taps and dies. Luckily he had a 1/2″ x 26 BSB tap and die, so we mounted the casting (which I had already cleaned up) in his Hardinge lathe.  It was a delicate job to grip the casting by the 1/8″ deep rough shoulder on the top and get it centered and small center drilled in the end of the spigot at the other end.
 
 
We could now reverse the casting and machine the top end
   
 
The top end was bored out to ensure hole square to casting and then drilled 11.5mm ready to be tapped 1/2″ x 26 BSB.
With this done I returned home to continue the job.
The Fuel Orifice Cap casting was first on the list.  This was put in 3 jaw chuck and the end to be threaded turned down to 0.6″ diameter.  This then set up in hexagon collet block and moved to mill and the six cast faces machined to give 11/16″ AF size.
 
Back to the lathe and turned down to 0.5″ diameter.  A decorative groove put in the hex and a thread relief groove cut, faced to length and die used to put 1/2″ x 26 BSB thread on the end.  This was then checked for fit using the previously threaded main casting.
Rather than continue with the main casting I decided to make the various fixings for the Mixer so these could be used to test holes/ threads when done on the main casting.
The fuel union was a standard purchased item with 1/16″ x 27 NPT thread.  The Needle Valve fitting was a piece of 3/8″ brass hex with 5/16″ x 24 UNF threads each end and a 6-48 threaded hole through the centre.  I had to deviate slightly here as I did not have a 6-48 tap or die so opted for 5BA.
The valve was from piece of brass with 0.122″ stem and a 45 degree valve seat and a 0.430 diameter head.  Chucked brass up in collet with short stick out and put a centre in the end, then extended out of chuck and supported end with half centre.  Turned to the 0.122″diameter and then cut the valve seat and parted off.
 

[Twizseven]

I made a 1/2″ x 26 BSB short brass mandrel to mount the main body casting on for machining and set this up in ER collet block.  To machine the first part I needed this at 45 degrees, and I had intended to use Wixey electronic angle gauge, but I had been lent a nice Hauser Jig Borer vice with very good angular scale and accurate pin detents for useful angles.  This was set to 45 degrees with the collet block fitted and the Needle Valve Boss set to be vertical.
 
This boss was faced off to give distance of 1.06″ to an imaginary point on the centre line of the casting where a hole through the needle valve boss would intersect.  A further 0.187″ was then removed.  Double checked that I was lined up on centre of the boss using a 7/16″ drill blank, then drilled 6.9mm 0.4375″ (7/16″) deep.  Hole was then tapped 5/16″ x 24 UNF.
The plans specified that the fuel jet should be done with #65 drill (0.0350″).  I do not possess any, but a 0.9mm drill is only 4/10 thou bigger, so that was used.  I found my smallest R8 mounted Jacobs chuck, fitted drill in it and set mill to its fastest (4600rpm).  The mill is a like a Bridgeport on steroids, which I felt was bit big for this little drill, and I did not want to break it in the hole of get it to suddenly pull in.  I carefully pecked at the hole and gradually lowered the  quill using the depth knobs to lower it a few thou at a time.  All went well and it broke through into the hole in the centre of the casting without any issues.
 

I test fitted the fuel needle valve and it all felt good.

The vice was now rotated over to put the Air Intake Boss uppermost.  This was faced off 0.656″ from the of the casting, hole centre location checked, 0.8227″, from end face of the casting and then drilled 8.5mm and tapped 1/8″ x 27 NPT.  I had already made the inlet pipe so checked fit of the thread.

The collet block now turned through 90 degrees to put the Fuel Inlet Boss uppermost.  Boss faced off 0.750″ from centre line.  Centred on the boss using 7/16″ drill rod, this should be 0.5″ from end face of casting.  Boss now drilled 6.3mm diameter for 0.310″ depth.  This depth is critical so as not to break through into the holes in the cored area of the casting.  Hole then tapped 1/16″ x 27 NPT and fit of fuel connector checked.

Casting now switched to smaller collet and held by the chucking spigot and the register at the top centered using co-axial dial indicator.  Casting now drilled 3.1mm down through the centre and well into the chucking spigot.  This hole then reamed to 1/8″
   
I now needed to cut the valve seat.  This needed to have 45 degree face and be 0.447″ diameter.  I went through all my countersinks and they were either too small or too bog to fit through the 1/2″ threaded top bore.  I hunted through all my end mills and champher cutters but nothing suitable.  Finally I found a brand new 10mm carbide spot drill.  The cutting end was reduced compared to the shank, but the shank would just go down the bore.

Because the seat was deep down a hole I could not easily (even at all) see progress.  In the end I wound the knee up until I could hear a cut being taken and then zeroised the knee DRO.  Would knee down and checked cut, would it back up, took 10 thou cut, zeroised the DRO and wound the knee down again.  Each time I checked to see where the fuel jet hole was.
   
I continued like that until I had the fuel hole in the center of the seat and the seat to the maximum diameter of the cutter I was using.  The hole can be seen in the picture above.  In fact I went a bit too deep, about 6 thou, so used an end mill to remove the slight lip.  A bit Heath Robinson but it worked.

[Twizseven]

The next fun bit was the hole to link the fuel inlet boss and the needle valve boss.  This needs to be 3/32″ diameter and must NOT break into the central area of the casting..  This required some careful lining up.  The other issue is drilling into the side of a thread the drill will wander.  The pictures show the story easier than describing it.  I did use a tiny end mill to give me a flat spot to drill, followed by a long centre drill to put a pilot hole.
    
In theory I was meant to drill a return hole from the needle valve boss so the two joined up.  I did not need to do this as I broke through into the base of the tapped hole.  I reset the casting in the collet chuck and cleaned up the broken through area using a small end mill.

I cleaned up both threads using the appropriate taps and then fitted the needle valve and the fuel inlet union and checked that I could blow from one to another with the components fitted.  All was okay.

The casting was then remounted on the mandrel, moved to the lathe and the chucking spigot removed.  The various bosses then cleaned up with file and a trial assembly done.

I had to shrink the diameter of the valve slightly to match the size of the valve seat. I machined a small slot in the top of the valve so I could use a screwdriver blade to lap the valve in.
   

[Twizseven]

Now getting there.

Still ned to do the fuel pipe and fit the fuel tank base plate and JB Weld it into place.  Still deciding whether to peg the main bearings to ensure they cannot rotate and block oil feed hole.

I have set the timing and I can see the inlet valve being sucked open and making a “sucking type” noise and can feel air being pushed out of exhaust.  So looking hopeful.

[Roger B]

Excellent  That's a complicated mixer  I think I will stick with fuel injection 

[Dave Otto]

Nice work on the Lunk mixer! I have made a few of them and they are fussy little guys to get right.

Dave

[Twizseven]

Decided I really ought to pin the main bearing bushes, so set the main casting back on jig plate at 25 degree angle.  Put 1/2" Drill blank through bearings and used this to centre up on bearing and then centered up between the main bearing bosses.  I had some 5/64" silver steel and planned to use this for the pins.

Removed the drill blank and moved to plus 1.219" and drilled through the drilled oil feed hole through top of bush and then through bottom of bush  and then 0.125" into the casting.  Repeated this at minus 1.219".

Whilst the bushes were still fitted moved to a 3mm dia drill and just drilled through the top hole in each bush to aid with oil feed.

Removed the bushes and moved then over to the Myford into a collet chuck.  I wanted to turn a groove to allow oil to spread around the bush.  Used a 0.064" parting tool.  I was about to switch lathe on when remembered I did not want to remove any material adjacent to the lower pin location hole. Fitted lathe mandrel handle and turned spindle by hand but started cut about 0.625" (1/16") away from pin hole and stopped in similar position having gone almost full circle.  Three passes was enough to get a small groove.  Repeated for second bush.

My ER collets did not go small enough for the pin but I had 5/16" 5C collet.  Parted two pins off to calculated length of 0.185".  These were a little too long and I was worried they might mark the crank so removed a further 15thou.

All fitted together satisfactorily.

Now to JB Weld the fuel tank base into place.

[Twizseven]

Now to JB Weld the fuel tank base into place.

The main casting had already been drilled and tapped for 6 small screws to hold the stainless fuel tank base in place.  A thin bead of JB Weld was run round the recess in the main casting and then the stainless panel screwed into place.

The excess JB Weld had squeezed above the panel and this was supplemented by a further bead of JB Weld and the fillet smoothed down into place. 
 
Let’s hope it does not leak.  Time will tell.

I was waiting for a small collapsible spray booth to be delivered and so used the time to make the final few nuts, bolts and studs required to hold the main casting, base casting and the wooden skids together.  I also masked up the parts ready for painting.
 
The collapsible spray booth arrived and then had the task of making an extraction system and some lighting for it.  Some thin ply, a cheap bathroom extraction fan, some spare aluminium strip and sheet and a filter made up a working extraction system.  It would suck a sheet of paper towards the filter, but it was only once I started to spray I could see how effective it actually was.  I had 4 10W LED lamps brought cheaply from a local business that was closing down and these provided directional lighting.
 
3 coats of grey primer were applied to all components.
 
This was followed by 3 coats of top colour.  Base casting, Flywheels, and Pulley were painted Gloss Black, Head with heat resistant matt black, and main casting with Rover Brooklands Green.
 
I had given the flywheels and pulley a good polish prior to masking up.  I will give the paint 48 hours to fully harden and then clean up any overspray off the bare metal areas.

Then hope it all goes back together alright and the fuel tank holds fuel.

Colin