Recycled Flyer

Hey Martin,
about the flat plate mounted carb, it does make it hard to change venturi size though when the more common cylindrical inserts can simply be spun up on a lathe.
Imean how does one reduce the ID of the bore if the diesel conversion requires it?

Do Ido like to call stuff like this .............. character! (Or a challenge - depends if you are a glass half full kinda guy or not.)

Cheers.

AMB

Recycled flyer being a flat plate mount maybe make one up, drill force fit a piece tubing in it you could even use say 1/4 inch use longer screws to secure then add any varient of a carb you want, then again the engine on diesel should go full tilt about 75% open on (r/c) carb martin

earlwb

The flange mount carb is easy to handle. It has advantages over the insert round carb into a round hole kinda setup. as the drawbar clamp or screws on the side can cause problems like leaks or warps. it isn't difficult to make adapters for it, if you want to try different carbs on it. The new carb uses a barrel instead of a butterfly valve, so one can insert a restrictor if they want to. I think that the older butterfly carb has a smaller intake venturi over the newer carb.
 
 

AMB

Ok group Just got off the phone with Bob Davis we got into the Fox thing EVERY FOX IS STILL TEST RUN BEFORE IT LEAVES THE FACTORY
the 15 is a very engine strong on glow and monster power with a diesel head martin

I believe it will out preform the Enya 4 strk 36 diesel , waiting to see what Fiery gets on the fox15 with the davis head

earlwb

That is one of the great things about Fox engines, is that they test run every engine they make.
How many other engine manufacturers do that?
How much is DDD selling the Fox .15 diesels for?

Mr Cox

I believe PAW are running all their engines too, while ABC engines don't need any running at the factory.

earlwb

I am not sure PAW tests their engines. I remember people complaining about defective PAW engines before. I think one USA importer was checking each engine before they sold it to a customer, but I don't think he test ran all the engines either.

AMB

EarlWB PAW does indeed run all their engines before shipping, Bob Davis mentioned this too this came up when we were talking about Fox running theirs

Eric Clutton ( Dr Diesel) who lives near Davis in Tenn reruns them and writes the compression and needle settings on the box before he ships them martin

Recycled Flyer

Well Earl, if PAW do not test their engines before selling them they would be lying to the public as their own printed matter tells us that they do.

Iam going to go to believe their paper work on this one until proven otherwise.

Ibelieve that they state 'up to 10 000 rpm' but a weak and defective engine could easily reach these speeds so all that it does prove is that the product works in some fashion.

AMB

Hmm looks like something CS needed to do martin

Quite sure a few do not make it out the door at Fox or PAW at least they catch them

earlwb

That is good to know. But if they have defective engines it makes one wonder how they made it out to the customer then.
I knew Eric Clutton test runs the engines to be sure though.

AMB

EarlWB the Fox 15 with davis head and glow head is 139.95 + shipping martin

Recycled Flyer

Define 'defective' in this context.

Perhaps anything that achieves 10 000 rpm - isn't, anything that doesn't - is.

Kind of a silly line in the sand to draw when almost every engine in their range should be well capable of far more than this.

Imean, would you buy a high revving combat special that can only hit 10 000 rpm safe in the knowledge that it has passed their standards test?

Far better would be an actual recorded reading dated and signed, and with useful stuff like the prop used, fuel etc (just like a certain Australian Team race engine builder used to do.)

earlwb

Well PAW apparently had some kind of a problem with production as there were a number of engines that didn't work, no power, did not run, failed right away, parts not fitted well, etc. Eric Clutton was fixing engines and test running them before he sold them to get around whatever it was. There was a thread here or in the other forum group about it a couple of years ago.
Maybe it is a moot point now, they may have corrected the quality control issues since then.
But since Dr Diesel is test running the engines before he sells them, I would buy from him to be sure.
I do have several PAW engines myself too. A .06, .19, .29, and .35. Maybe a .40 size I forget now for sure.

Thanks AMB

Mr Cox

I have not had any problems with the engines that I have bought directly from PAW during the last 3-4 years (this has been engines ranging from .55cc to .15ci). The engines all come with the compression setting within about a 1/4 of turn from a running position.

earlwb

That is good news. I think whatever I read in the past must have been in error or I am becoming senile instead. Hopefully not.

aspeed

I am sort of rerouting the thread a bit, but I made a bigger venturi for a control line carb, and it didn.t go any faster, so I checked a couple of things, and found the head had .045" clearance (It is glow, I know wrong thread)  I wonder if I should take off .025" for a power gain.  It didn't compare well to other motors of it's size.  It could be they wanted it to pull bigger props, or not burn out their plugs?  I don't want to machine my sleeve for nothing, but I have never seen another motor with this much clearance. It may make a contender out of it?  I could maybe make another head with a Turbo plug to try.  Just thinkin, the field isn't ready to fly from yet.

controlliner

For clearance between the squish band and the piston crown, you can have .019 clearance.

Mr Cox

It is better to machine the head rather than the liner. Just remove material from the head and you can use shims to get back to what it was before. Should you mess it up completly you can always get a new replacement head too. Compression ratio seemed okay on mine though, while the poorly made intake was a power robber.

It will never reach the power of a Norvel .15 though, never mind power to weight ratio.

I saw that you tried the larger intake on the Norvel (I'm surfer_kris on rcgroups), great engine isn't it?

controlliner

Mine have a .250" intake with a head button I made from bar stock and it has .019 clearance on the squish band. The strange thing is with the spray bar in the .250 intake, I don't need any pressure. I must take a tach reading when I get a chance.

aspeed

The head shape has no real squish band, just a nice shaped dome. Venturi size is really changing what I had always believed in, bigger is better until you can't get a setting. The Fora I have doesn't run on suction at all, the needle is out all the way and it is still too lean, and the Fox and LA .15 don't really go much faster with a bigger venturi, and then the Norvel and the AP turn into a completely different animal when opened up. The LA has a fairly small intake window that probably restricts it. and maybe the Fora needle valve has a small hole restricting the flow maybe. I guess a new turbo head button for the Fox is in order, unless the grass gets growing on the new field soon. The lip on the stock head is already pretty thin to remove .025". I am still not sure about the diesel thing yet. I had a bad experience as a kid, everyone else could start my Frog .15 except me. Everyone else being team race guys of course. I could make a diesel head myself, but probably couldn't get it going without a starter, and risk breaking things. I have a Hardinge Chucker lathe begging for some time. Oh I just checked an old Rossi head button. It looks almost drop in and has some meat on to raise the compression. Then I can check rpm with a standard Rossi plug, a short reach and a turbo plug if I grind up a toolbit for it some day.

fiery

My Feedback: (2)

Fox .15 BB R/C with DDD head (Schneurle, iron piston in steel liner)

Date: 13th May 2012
Temp: 28 C.
Humidity: -
Elev: 400 feet ASL

Props tested

1. Master Airscrew Scimitar Profile 9x7 (US)
2. APC C-2 9x4 (US)
3 Bolly Clubman 9.5 x 7 (Australia)
4. Robbe Dynamic 9x6 (Germany)

DDD recommend to start with a 9 x 7 on .15 size engines.
Notes:

Engine run in as glow on 80:20 fuel, no nitromethane. Six five minute runs following tips from Adrian Duncan for running in iron and steel P&L diesels, described here:

http://www3.bc.sympatico.ca/dieselco...ut_diesels.htm

DDD head then installed and engine run on the fuel mix:

25 % Castor Oil
38.5% Kerosene (KCB Brand)
35 % Di-ethyl Ether
1.5% Isopropyl Nitrate

Engine was easier to hand start on diesel. Ready starts hot or cold. Instant when touched with my Sullivan Hornet 1/2 A starter.

Engine ran cool at all times, even when adjusted to maximum.

Main needle 6/8 of a turn out from closed (turned in 1/3 turn from best glow setting). L/S needle not touched from best glow setting.

No leaks from muffler. Muffler screws never came loose after inital tightening.

Excellent throttle response on glow or diesel. Twin needle carb is outstanding. Carb spigot seals without an "O" ring. It relies on it's interference fit to be airtight. Metal throttle lever, now rare, is welcome. It has a proper throttle stop screw as well, often deleted in many recent R/C glow carbs.

Main needle spring was overly tight as delivered. H/S needle spring tensioners/ratchets were opened up to reduce tension, and permit easier H/S needle adjustment.

Deep knurling on prop driver and inner face of prop washer make for serious prop security

Engine exterior casting has a bead blast finish. Nice but not exceptional.

Interior of engine clean and free of swarf as delivered.

Fit of DDD head is a very good sliding interference fit into liner. Stock glow head fit is a little loose for my taste. One head shim/gasket fitted in each case (two supplied with engine)

Very little blow-by past the contra piston sealing "O" ring in the DDD head. Slight squish band and deepish dish shape on the contra piston facing the combustion chamber. Best compression and needle setting were very easily found. No leaks from head, backplate or carb.

Peformance on diesel.

Refer to images and youtube video in following post.

Best RPM 12,000 steady WOT with APC 9 x 4. Engine would idle safely down to 3,500 rpm. Best idle unsurprisingly on the Robbe Dynamic "paddle" broad blade" prop, the heaviest of the group. No attempt made to optimise L/S needle. I overlooked it. Pick up from idle was very good as found on best glow setting with only slight hesitation after extended idling.

Operation with DDD head as simple and reliable as it can get. Engine feels engineered to take lots of work. Mounting lugs are very substantial. Split cone attaching prop driver is larger than found on most engines three times it's size. Lots of surface area.

Conclusion. The Fox .15BB with the DDD head is a sound work horse for nice smaller scale or sports model. Made from quality materials. Unfussy to run, not a highly strung show pony. DDD diesel conversion head is very nicely done. Engine and DDD head well thought out overall.

At $73.50 (at time of posting) for the engine (excluding the DDD head) great value for money. With the DDD head, a winner.

fiery

My Feedback: (2)

Further images.

For video of the Fox spinning an APC 9x4 click on link below:

http://www.youtube.com/watch?v=4jEoS...ature=youtu.be

And spinning a Robbe Dynamic 9x6 , click on this link

http://www.youtube.com/watch?v=xViwv...ature=youtu.be

Mr Cox

Thanks for sharing, there seems to be quite a lot of "knocking" to me though, have you tried with a lower compression setting?

AMB

Fiery , smooth as silk great transitions, very clean running too sounds on the money

Mr Cox I could not hear any knocking a little exhaust pop or gurgle on transition very little, maybe some background noise wind excetra
one of the smoothest running engines I have seen, and heard martin

I have 3 MVVS 15 diesels, great engines , however after seeing this, hearing runs, transistions, this one I am getting one

I have o issues setting up my MVVS 15s yes classic design contra in cylinder , but with the Davis head contra in head is easier
to set and handle, have both MVVS, PAWS in the classics , the rest various engines Davis heads