Cirrus V8 rotary valve engine build 2x scale up

[mattty]

Love the engine. can't wait to hear it running.

 

[bazmak]

When i first started i checked stock of alum.I bought 2 pieces for the sump and crankcase but had had enough matl for 8 cylinders.So first job was to saw and mill to size 8 pieces nom 32x38x63.I made shimmed packs to give me 38x38
so i could hold central in 4 jaw SC chuck and centred all 8
Now i could perform small ops on each and remove / refit and keep concentric
as accurate as chuck.Then setting stops and using dials i was able to perform
a no of ops to all parts.PHOTO REPLACED DOWN THE LINE

 

[bazmak]

Next job was to drill the cylinder fixing
I made a drilling template from 3mm plt located on the cyl spigot
and drilled all holes 3mm.Made a location spigot and drilled all
holes 3mm in crankcase.Crankcase was then tapped M4 an the cylinders opened out to 4.1mm.Cleaned everything up and trial fitted together
Next job will be to make the pistons and bore out the cylinders

 

[johnmcc69]

That's looking real good Baz!

John

 

[bazmak]

Next stage was to bore cylinders and make pistons

 

[bazmak]

Next is the first stage of assy of the above.Just a note .I first ftted all cyls as individuals so each cyl can be checked.If you try all 8 together it is difficult to isolate any binding on any particular cylinder.In this instance i was able to isolate bad interference on cyls 3 and 6 and remedy easily.The next stage is to assemble all 8 and turn over

 

[10K Pete]

Those are some really beautiful parts! Just itching to see it together.

Pete

 

[bazmak]

Its looking nice and the right size.The original would have been too small
One problem is that i drilled the cylinder head for the inlet and exhaust valve
the wrong way round but i have a simple solution.I dont like or trying to make
the 90o elbow in the 3/16 supply pipe and always intended to make a combination manifold to make manufacture easier.The brass manifold i intend to let into the head and also form a new ball valve seat in brass,after i have drilled the spring hole thru.Still in my head but resolve itself when i get there
Merry Xmas

 

[Herbiev]

I love the lapping tool. Great idea. Im always having trouble with those brake cylinder honing stones

 

[bazmak]

Its an oldie and cheapy Herbie but its always worked well for me.
Last few ops this morning before Xmas
Assembled all 8 cylinders and it turned over well.Set up in the lathe and run in for a few minutes with plenty of WD40 before stripping down.All freedup nicely no high spots to take off.Bored out the crankcase and turned the crankshaft
and fitted outer ball bearings

 

[bazmak]

Happy new year all.Further progress not made easy by our inclement weather
We have had a week over 100c peaking at 110c but 130c in my shed
Cant really complain as we have not had,floods,blizzards tornadoes etc
my sympathies go to all UK and USA residents affected
I did not envisage all the difficulties produced by scalling up x 2
First job was to drill the CC 11.5mm 3"" deep from each end and hope they line up.Careful setup in the mill and looking good.I could not get suitable tube for the bush so made from 1/2" dia x 7" lg brass.Few problems but final success
I made and fitted 8 no brass nipples and drilled thru into the bush.Photos show all,i am very pleased so far,limits and fits were to me perfect
One point of note.When i turned and finished the o/d of the brass the first skim in the lathe gave a 6 thou taper.Fortunately Sieg had delivered the goods
on the SC4 and there were 2 easily adjustable grub screws to adjust the tailstock.A few minutes was all it took to adjust the tailstock to turn to 1/2 thou over 7" length.Turned to +1thou and then nudged/fitted to light push fit in crankcase

 

[dsage]

Bazmak:

>> We have had a week over 100c peaking at 110c but 130c in my shed

I think you mean degrees F right?

Water would be boiling sitting on the table at 100c.

Nice job on the engine. Looking forward to seeing it run.

Sage

 

[bazmak]

Yes degrees F for our american friends.Poms are still both but for ozzies etc
40/43 or 55oc inside

 

[bazmak]

Next job was to fit the valve stem.I polished a few tenths off the high spots
then set up in the lathe to run in for a few minutes with plenty of WD40
in the nipples.Cant believe what a good fit it is after drilling and reaming from both ends over 7" long

 

[bazmak]

Next job was to pipe all the cylinders,but with design changes and upscaling etc
i did not want to produce 8 each of all parts then find problems so decided to just complete i individual cylinder and finalize details and dims.
I did not want to make the tight pipe bend and intended to make a simplified manifold.As i mentioned previousley i had drilled the valve holes in the head the wrong way round.Many solutions involving a lot of work but the best one was not the most obvious.Leave the drillings as is and let the manifold into the head anf form the ball seat.The spring and ball could be fitted from the pipe end the the other side adapted for the exhaust.I made a new manifold and flare nut.Made a fixture to flare the 3/16" pipe then nudged everything to fit.Minor problems were sorted and the final dims noted.Now for the next 7

 

[bazmak]

While i am finishing pipeping the cylinders i am starting to give thought to the pair of gears.13t and 26t.I have never cut gears and know very little.Not worth buying a set of 8 invalute cutters and reading about the nonclenture is making my head spin.Here are my thoughts,hopefully someone out there will be able to advise/comment.The centres are fixed,double the scale i assume means i need
a 26t and 52t ?? The 2/1 ratio drive i think is critical Pressure angle is given at 141/2o and dias need to be doubled
I plan to make a single point cutter and cut on the mill with a deviding head I have change gears from the lathe.If i grind a tool to that form and make a pair in alum,will that work.Any input before i start will be most appreciated

 

[Cogsy]

Doubling the tooth count on both gears will double the centre distance of the shafts so that works out nicely for you, and of course you need to maintain the 2:1 ratio. However, the outside diameter of the gears does not exactly double, it is the PCD of the gears (the point where they mesh) that doubles.

You will need to do the math using your DP, pressure angle and tooth count to calculate the OD required for the gear blanks. I've never made a single point cutter (looked too tricky to get it right in the size I needed) but I have used this site LINK to make a straight hob that does the job well.

Alternatively, you may be able to use gears with a different mod/DP and tooth count to achieve the centre distances you need, or even the original gears specified with idlers between them to form an interesting gear train.

 

[bazmak]

Thanks Cogsey,i think i am missing the DP from the drawing,all i have is pressure angle,centres and diameters.I have ordered the book by Ivan Law but i need more info on the tooth form before attempting to make a single point cutter.Question,does the Dp change with no of teeth?. When i made the tumbler reverse for for the Advance lathe i used Myford gears which were 20dp
and 14.5 Pa. Dp i found out was the no of teeth on a 1" dia gear. I really need to work backwards as the fixed ctres and dias given with the no of teeth must
determine i assume the Dp. Tooth form is unimportant as these 2 gears only mesh together so could be any form that fits my fixed criteria.Will try and sent a private message to Chuck Fellows.Keep on with the input Regards barry

 

[Cogsy]

does the Dp change with no of teeth?

Not really. DP is how many teeth in 1 inch, so 25 teeth in one inch would be 25DP. Module (Mod) is metric and is the distance in mm between the teeth, so a Mod 0.8 is 1 tooth per 0.8mm. To change Mod to DP simply take the mod number and times it by 25.4 to give DP. This works out teeth per inch. eg Mod 0.8 x 25.4 = 20.32 DP. To go from DP to Mod just divide DP by 25.4 to give the Mod eg 25DP / 25.4 = 0.984 Mod - close enough to use Mod 1 probably.

If you increase the DP the tooth count for a given diameter gear gets bigger as you can fit more teeth in per inch. For a Mod, if you increase the Mod you are making the teeth larger and tooth count goes down for a given diameter.

As far as your application goes, the tooth form has to be reasonably accurate so they will mesh, plus your blank diameters have to be spot-on so you get the correct number of teeth, with the correct spacing all the way round.

Edit to add - I don't know if you will be able to make these two gears with a single point cutter as they have such different tooth counts. I suspect you'll have to make a cutter for each gear. As the tooth count goes down, the relative curve of the gear increases and a different tooth profile is cut so it will mesh with other gears of the same DP or Mod. This is why a full set of 8 cutters is needed for all tooth ranges per Mod or DP. The straight hob I linked to uses a different method and you only need to make one of them per Mod or DP.

 

[Herbiev]

Thanks for the link Cogsy. That saves making different single point cutters for different gears