Len Mason's "Mastiff" - chewed from the solid

[deltatango]

The last bits needed in the timing case were the timing gears and their associated nuts and washers. This looked straight forward but turned into a bit of a catalogue of disasters.
Two 40DP gears, 35 to drive 70 teeth, were supplied by Hemingway but (in contrast to the helicals also supplied) were a bit rough in the finish. There were a lot of burrs and I had the "brilliant" idea of fitting the brass wire brush to the off-hand grinder and running the gears under it. I now know that brass at that speed is almost as hard as whatever the gears were made from, the burrs disappeared alright but so did all the edges on the teeth (and worse, see later).  I machined the soft jaws to fit each gear in turn and bored the mounting holes to really good fits on the crank shaft and the mounting centre for the camshaft. The other thing I had actually got close to correct was the centre distance between the shafts (+0.002", just enough to guarantee clearance, I thought)  but it wasn't to be. When I fitted the gears they would bind up tight in several places and weren't free running anywhere - I'd wire brushed them eccentric and I have to think they must have been a bit over size to start with.

I messed around making slightly eccentric bushes but couldn't fix the problem that way and finally bit the bullet and ordered the necessary 40DP gear cutters from the UK (RDG Tools). RDG sent them off very promptly, tracking showed the UK courier got them to Oz in 4 days (great! I thought); it then took me 3 stressful weeks to extract them from the grasp of an utterly incompetent local courier company.

With the cutters finally to hand I machined up some blanks (and spares):



and cut my first-ever gears. First the 35 tooth:



and then the 70. I didn't use cutting oil with this one and the finish was pretty much the same as the other:



I light of the previous experience with binding I over cut the tooth depth (0.056" rather than 0.054") but I should have had confidence in my measurements as the end result was more clearance then necessary:



If these prove too noisy, or wear too fast in use, I can always make a new set.

The camshaft gear and its mounting sleeve are designed to provide some "Vernier"adjustment of the valve timing with four holes in the mounting at 90 degrees and four in the gear at 91.2. the holes in the gear are tapped M3 and a single CS screw goes in whichever hole gives the best timing. To make the drilling and tapping easier I spent a few hours making an ER32 chuck with a MT2 mandrel to fit the centre hole in the rotary table:



The last act was to fit the timing case to the cylinder block, check the meshing of the auxiliary drive gears, and drill and tap for the screws. The final result:



Everything runs smoothly, if a bit too freely. Maybe the most difficult bits of Mastiff are now behind me?? Anyway I can now go back to carving Ali billets for the cylinder blocks and heads and Mastiff will start to fill out and look more like an engine.

DT

[steamer]

Nicely done!    That'll work fine I'm sure!


Dave

[ozzie46]

Hope you don't mind but here is a video of my Mastiff running.  I changed the distibutor to the top because Oil was getting into the dizzy cap.



 I had to rebuild the engine . I didn't leave enough clearance for an oil film on the rod journals and ended up having to remake the crankshaft and new rods as a rod started knocking.

Ron

[zeeprogrammer]

I've been following along and enjoying.

Thanks Ron for the video. I didn't know what a Mastiff was so now the build will be even more enjoyable.

[deltatango]

Ron, thanks for the video of your Mastiff running - I certainly don't mind seeing it hear, its good to see and hear one actually running.

I've looked at the distributor location myself and thought that the conventional (and less oily) place would be on top of the contact breaker. However, right now I plan to build the engine more or less as drawn then look at fitting electronic ignition, maybe a pair of double-ended coils and a waste spark system (we've owned a bunch of Subarus over the years and it works for them...). Thanks for the hint re the big end clearances - I've made the crank but not the rods so I can take care when I get to them. What range of RPM does your Mastiff manage?

Carl, glad to know that you are following along.

David T

[ozzie46]

I haven't had a tach on it but it will rev up pretty good once it warms up.
I have a hall effect ignition on it. I built the circuit that was on HMEM a while back by" jgedde" and "dsage", 2 or 3 years ago I think, I used a coil off of a junked out motorcycle and made my own spark plugs with corian for the insulator. They are 1/4-32 thread. Also I used 2024 aluminum on the second set of rods.

 Ron

[ozzie46]

Put a tach on the Mastiff today and got a reliable idle at 1000 to 1200 rpm. It has a nice "bloop bloop" sound I really like at that rpm.  It will rev up to about 4500 rpm. I'm afraid to go any higher.
 The tach is a Shimpo Laser tach. It will read by laser or direct contact.

 I may be able to get a little lower idle rpm if I tweak the carb some more.

 Ron

[90LX_Notch]

Still following along David and enjoying this build very much.

-Bob

[deltatango]

Many thanks for the info Ron, I can't see myself wanting Mastiff to rev over 4500 but a slower idle would be good, have to wait to see what happens.

Hemingway supplies spark plug kits that use a ceramic bead for the insulator, Corian would be a good alternative. I've bought in a 1/4 x 32 UNEF (AKA UNSpecial) tap and a die, hope this is the right one. The "1/4x32" is often quoted for the plug thread but I've not seen the thread form actually specified; 1/4 x 32 ME is a Whitworth form and common on UK-designed projects.

Bob, I'm pleased you are following, hope to make some more progress soon. Right now we have UK visitors staying and, just to keep things interesting, we are about to drive 5 hours into the mountains for our niece's wedding, back on Monday. I'm still not quite sure why she wanted to be married on a mountain top at 1800m altitude...

DT

[MJM460]

Hi DT,

I hope that by the time you return, you will understand your nieces choice a little more.  You can be sure that only much loved relatives and closest friends are invited to such a location.  You are one of the  privileged few.

  Five hours, eh?  Perhaps Falls Creek or Hotham?  My gues is that she would have preferred it a little colder than likely at this time of year, but then it would be really hard to convince some of the much wanted guests to attend.

MJM460

[deltatango]

Hi MJM460,
It was Mt Hotham and the weather held off long enough for a really beautiful outdoor, mountain top, ceremony. Not something anyone wanted to try much later in the year (I don't think there are any skiers in the family, certainly not among the older generation).
DT

[Roger B]

Still following along in the background     

I used a 1/4 - 32 plug (from Just Engines in the UK) in my vertical engine. I purchased a tap from the local ME supplier which I guess is ME / Whitworth profile. I never checked, but it seems to fit together 

[Jasonb]

Yes 1/4 x 32 UNEF is the one you want for plugs

[Art K]

DT,
I have used some Whitworth on stuff at work. I think the size refers to the wrench size and not the actual thread size. For example the one that is basically a US 5/16- 24 thread is a 1/2 Whitworth wrench. Go figure.
Art

[deltatango]

Thanks Jason, Its good to have the plug threadform cleared up properly. I'll use the 1/4x32 UNEF tap for the plug threads then it is correct for commercial plugs if those prove necessary. The matching die is marked UNS I'm guessing this is UN Special but as long as it matches the tap then that's OK.

1/4x32ME would probably work as long as the fit isn't too close.

Now back to carving Al blocks - Six in total, cylinder block, head and head cover. The cover and head will be glued together to form a single unit when the coolant space has been machined in the outer surface of the head. Len Mason suggests Araldite for this, I'm tempted to use JB Weld when the time comes; if the Forum has advice/experience it would be good to hear it. Thanks.

I started with squaring up the cylinder block blanks to the "envelope" dimensions using the high speed head on the Aciera F3 for the first time:



but found that the HS head spindle was, very slightly, tilted towards me in the YZ plane and the face cutter was leaving shallow ridges in the work. This should not be possible and I haven't yet plucked up the courage to strip the whole head down to find the problem. I'm guessing (hoping?) that the spindle is not fitted correctly but there may be burrs or dirt in one or two surfaces. Anyway I changed to the standard vertical head and a 16 mm cutter for the rest of the pieces:





I'm also going to make the low profile clamps described in the current MEW before doing any more work on thin pieces. There weren't any disasters but I did add an extra downward clamp later in the work:



The end point of this stage was six blocks ready for a lot of the metal to be turned into swarf:



and starting with the coolant entry and flanges on the blocks:



and the outlets on the heads:



After that the three parts were stacked up in a nest with the 9 fixing holes (I'm using M3.5 cap screws for the heads) and the two spark plug holes marked out. I don't have a DRO so finding the centres used a needle, and the fixing holes were drilled through into the block tapping size and opened out to clearance size through the cover and head:



The plug holes drilled and counter bored:



The covers were removed, the fixing holes in the head tapped M3.5 and the coolant passages marked out on the heads. These were fixed to the head with cap screws and the pack clamped back into the nest to drill the holes:



After drilling and tapping the remaining coolant passage holes in the sides of the blocks and heads I now have two sets of holy pieces of Al alloy:



The cover plates are complete apart from cleaning up but the heads and cylinder blocks have a lot of complicated detail to be carved into them. I'll be taking this carefully!

Regards, DT