Modified Fox .35 comparison ??

OK, if a Fox 35 is modified like Larry F. does, hemi, stuffer, 10-15% nitro: What "modern" engine(s) would one expect it to perform like?
Power wise, etc.,?
Thanks
Bill <><

A FOX that has been re-worked by Larry Foster.
The engine will have MORE grunt.
The engine will give you a CLASSIC 4-2-4.
The engine will be easy to start.
The engine will not burp on the outsides.
The engine will run in it's power curve and stay there.
The engine will win you over.
The engine runs the same upright and inverted.
The engine will make you happy.

scott(and I don't own one)Riese

Thanks Scott,
But can you give me an answer to the question of what it might compare to?
I have 40 FPs, OS 32Fs, Webra 32, and a recently accquired TT 36.
(These have all been reworked to stunt timing, and are very good engines.)

Bill <><

Bill,
This always "depends".

If you have modified the above list to do 4-2-4, the Fox MAY be just a bit weaker. If on the otherhand you are running them in low pitch-high rpm mode, those engines are likely to put out substantially more poop--even accounting for less possible prop efficiency at higher rpms.

The real issue is to compare to the FP/La25 plain bearing engine and clones. My own feeling is that the Fox has more grunt than those engines. This mainfests itself in more forgiveness in slightly overweight, or possible not superlight airframes. I have run the LA25 in light planes (Brodak Lightning Streak) and there it runs just great. For a heavier plane I have had some problems with the engine sagging. I know a few guys who feel the same way.

I think you need to try out some of these things for yourself. There are a lot of variables in anyone's own setup.

Thanks Alan,
The "modern" engines I have are set up to run 4-2, albeit at higher rpms than the Foxes I have normally run.
I am looking towards the Fox for "Classic" applications, but want to know if anyone has really *compared* them.

I plan to do the mods that Larry suggests, and have done one with the "older" mods. Found it to run much smoother, and probably has just a little more "oomph", but the OS, and Webra, 32s and especially the TT 36 seem to really have a good bit more power.
I like a Fox 35, but in stock trim I feel it needs a little help.
Got addicted to "power".
Bill <><

I've had both a Brodak 40 and a L&J Fox on the same airplane, a Ukey 35. This airplane doesn't require a lot of power, but based on this simple test, they produce similar power running 10X5 props. On a wide blade 10X6, the Fox produces noticeable more power. The Brodak is slightly heavier, so the Fox probably has a better power to weight ratio. With Larry's latest Fox, there is not a significant difference in vibration, which is amazing.

Bench horsepower using optimum props probably would show the LA25 making as much power as the Fox, but I find it hard to believe that the way we want these engines to run on the props we use that it has the same inflight thrust. Besides, the LA25 is slightly heavier than the Fox.

>Thanks Scott,
>But can you give me an answer to the question of what it
>might compare to?
>I have 40 FPs, OS 32Fs, Webra 32, and a recently accquired
>TT 36.
>(These have all been reworked to stunt timing, and are very
>good engines.)
>
>Bill <><
>
>
>Dont worry about the mule going blind 'til you get the cart
>loaded!

Bill your question seem to me you wanted to know the differance between Standard Fox and Reworked Fox.
After rework It's still a fox. IT'S and .35 cross flow engine. It's Compared to a Veco .35, a McCoy .35, a Meco .35, K&B .35 and so on.
If you want to compare it to Modern engines...Stock OS.25 I think would be the closest to POWER as a Fox .35 re-work. The TT-36 OS-32F all run great HOWEVER, More power.
I hate useing the term POWER. Engines need to set for the plane size and weight PERIOD. REMEMBER there are .40's out there that have more "power" then a ST-60.....OS-40 VF Is one.

Scott(hope it helps)Riese

>If you want to compare it to Modern engines...Stock OS.25
>>Scott(hope it helps)Riese

I agree with Scott. The 25 OS FP is comparible in power, but achieves it with a higher rpm (and flatter prop) and is a lot smoother and somewhat quieter, muffler vs muffler. One minute I'm flying with a FP 25, the next minute a Fox 35, so I can judge pretty easily.

Bill: I have done a little tach research re the Fox improvements. Mind that these are ground values only.

Hemi head: No rpm improvement, but Bigiron says that there are differences in how the 4-2-4 break occurs, so listen to his explanation. There are a number of different hemi heads out there, too, with Fox and Marv's being just two of them.

Stuffer backplate: Worth about 200-300 rpm. The conrod is not wobbling on the crankpin as on the stock motor.

Here are some other Fox mods that one can play with, Michigan style...

1. True the crank to the piston

2. True the lugs to the crank

3. Take out the "step" in the venturi

4. Cut oil grooves as circles around the piston

5. Cut a oil groove in the front bearing

None of these are guaranteed to improve on a good Fox in the first place, however. Currell

Thanks Scott,
I gather, then, that a reworked Fox will not produce the same "power" as a reworked modern 32-36.
I guess I was a little too vague in my question, my bad. I am wondering if I can get a Fox that will perform good enough to replace one of those engines and still get the performance needed, that's the skinny of it.
Seems that for "performance" I should stick to the reworked 32-36 engines.
I have a FP 25 and FSR 25, they do howl, and with a flat prop will do just fine, but I still prefer the 4-2 engines for Classic ships.
On the 40VF- my son and I flew them for several years in competition, and they still perform quite well. In fact, a ST 60 size stunter I built is being sold before I ever flew it because of the VFs!
Thanks again,
Bill <><

My question is if an OS 40 VF has more power than an ST 60 why do we keep flying it on .015 lines? I think the engine size line size rules need to be changed. If my .015 lines with stand a pull test of 45 lbs I think they should be allowed to be used. Also the FP 25 with the same power as a Fox but able to fly on .012s. The Fox is now at a penalty over the FP 25. Time for flyers to take back their sport or get the rules changes. Going to weighing models is a hassel to do at contests. Outlaw in Olympia....Jim Johnson

James;

Check the competition guidelines from AMA page 50. The maximum size engine you can run on .012 lines is a .15.

When did we add the pull test of 40LBS for engines from 40 to 46?????

The pull test is not the same as the pull we feel at the handle, it is generally greater.

>My question is if an OS 40 VF has more power than an ST 60
>why do we keep flying it on .015 lines? I think the engine
>size line size rules need to be changed. If my .015 lines
>with stand a pull test of 45 lbs I think they should be
>allowed to be used. Also the FP 25 with the same power as a
>Fox but able to fly on .012s. The Fox is now at a penalty
>over the FP 25.

Are we back to "power = pull" again?

> Time for flyers to take back their sport or
>get the rules changes

Huh?

>My question is if an OS 40 VF has more power than an ST 60
>why do we keep flying it on .015 lines? I think the engine
>size line size rules need to be changed. If my .015 lines
>with stand a pull test of 45 lbs I think they should be
>allowed to be used. Also the FP 25 with the same power as a
>Fox but able to fly on .012s. The Fox is now at a penalty
>over the FP 25. Time for flyers to take back their sport or
>get the rules changes. Going to weighing models is a hassel
>to do at contests. Outlaw in Olympia....Jim Johnson

JIM...Talk to PAUL WALKER and read the rule book. ...4 stroks get 40% off the value...So a 40 vf is .015, and so is a 4S 56, make sence to me.

Scott(i went to whatsamata U )Riese

Bill,

If you have a well modded TT .36, what possible use (other than OTS) would you want a fox .35 for? I have both and I know whats going in my G' Nobler!

Ward;)

Here is actual testing I’ve done with a Fan Break DYNO. Ambient Temperature was 95 to 97 Deg. F. The Fox 35’s were with 28% Castor and 15% nitro. The Brodak was 23% ½ & ½ Oil and 15% nitro. The OSLA’s were with 23% ½ & ½ Oil and 10% nitro.

Engine Size Modification Propeller Torque Rpm HP
Fox .35 Stock 10X6 APC 33.6 10200 0 340
Fox .35 Fox Hemi-head 10X6 APC 35.2 10350 0.361
Fox .35 L&J Hemi-Head 10X6 APC 36.0 10720 0.383
Fox .35 Series 5 10X6 APC 40.0 10620 0.421
Fox .35 Series 6 10X6 APC 42.4 10560 0.444
Fox .35 Series 6 ABC 10X6 APC 41.6 10500 0.433
Brodak .40 Stock 10X6 APC 41.6 10720 0.442
OSLA .40 Stock 11X4 APC 47.2 10750 0.503
OSLA .40 Reworked 11X4 APC 48.0 10900 0.519
OSLA .46 Stock 11.5X4 APC 57.6 12360 0.706
OSLA .46 Reworked 11.5X4 APC 60.8 11644 0.702

>OSLA .46 Stock 11.5X4 APC 57.6 12360 0.706
>OSLA .46 Reworked 11.5X4 APC 60.8 11644 0.702

Larry, could you fill this in a little? The same prop, spinning 6 percent faster, requires 1/2% more power (vice 1.06^3 or ~20% more)? Are those numbers (57.2, 60.8) torque in some units? If so, it takes less torque to spin it faster? Puzzling, at least.

>>OSLA .46 Stock 11.5X4 APC 57.6 12360 0.706
>>OSLA .46 Reworked 11.5X4 APC 60.8 11644 0.702
>
>Larry, could you fill this in a little? The same prop,
>spinning 6 percent faster, requires 1/2% more power (vice
>1.06^3 or ~20% more)? Are those numbers (57.2, 60.8) torque
>in some units? If so, it takes less torque to spin it
>faster? Puzzling, at least.

The torque would be in ounce-inches.
That being so, HP = RPM x TORQUE / 1008406

Surely there's some experimental error in here.
Fan brake dynos are very sensitive to wind, and perhaps prop swirl.
Repeat the same test 10 times and we'll start to see some patterns.
On the other hand, no dyno is necessary when comparing engines
using the same prop. On a third hand, one usually uses a whole
range of props to get a feeling for the engine's power curve.
On a 4th hand, I would have tested the Fox with a smaller prop
(since a 10x6 would unload in the air) to get a feeling for in-air
performance.

The Fox motors and Brodak 40 were all run back-to-back three runs apiece. The LA’s were done a week apart with different conditions. They are simply a base line. I was reluctant to post the LA,s but thought it would be nice to see it. I currently do not have the time to post a lot lately so if I don’t answer posts for a while it’s not because I’m blowing you off. Right now I'm averaging 15 engines (rebuilds and upgrades) a week and building for VSC, plus I'm still recovering from Back Surgery.
People speculate on what engines really do, this allows me to see what happens when I change stuff, I’ve done a lot more with props and fuel also. I also want to let everyone no that I endorse Randy Smiths engines and Lew Wollards, I feel both do excellant work.

Hi Larry,
Thanks a lot for jumping in! I appreciate you posting this data.
I am going ahead with the Fox and see how it goes.
Thanks again!
Bill <><

Edit: It seems strange that the ABC Series 6 didn't put out quite as much torque and HP as the steel/iron Series 6 set up. (??)

Bill;
The ABC never has produced like the Iron Piston, I've never tried to figure out why, but it's a common complaint with the ABC. It does run much smoother though.
Larry

Larry, I have said the same thing several times before here in this and other message boards. I have three ABC Fox 35s. One GMA prepared and two Fox ABC P & C assys with Hemi heads etc. I can get better power from my steel/iron assemblies. They just vibrate a little more. I am currently flying my Novi IV with a Brodak 40 in it and for the previous year and six months I had a Fox stunt 35 in it. It is 630+ square inches of wing and weighs 44 to 45 oz. It flies better with the fox 35. BUT to be fair, I have messed with Fox 35s for lord knows how many years, and I have only begun to work with the B-40.
Bigiron

Marvin;
What I have found and you most likely too over the years is there are so many variables in a Fox 35. The only constant is you well find huge differences in machine work and the ABC is down on power. There is no secret in making one run well, only patience. If someone reworks a few engines and they run good they consider themselves experts. When someone like you reworks hundreds of them successfully then I would consider them experts. The good thing is the Fox 35 will always lend a good discussion.
Another thing for FYI is Randy Smith has just made 6 replacement Crankshafts in which I have 3 coming. In talking to him he has corrected all the problems and covered all the mods that are now being done to the Fox crank. Just trying to figure out who I can get to test them for me, Don McCLave is top of the list.

Larry: Could you please explain what you mean by Series 5 and 6 Foxes?

Currell,
Series 5 and Series 6 are references to Larry's "Series" of reworks.
Bill <><

Thanks. Maybe Larry can explain some of the things that he does for these Series, and perhaps the earlier ones, too.

>Larry: Could you please explain what you mean by Series 5
>and 6 Foxes?
>
>Currell

The Series 5 has these reworks:

Case:
Bushing hole and venturi blended.
Mounting lugs trued.
Mill the back plate surface true to the crankshaft so the rod doesn’t walk back and forth on the crank pin.
By/pass port filled in and reshaped. The volume of the intake port is reduced approximately 30 percent. The port is reshaped to increase volume with the flow path.

Liner and piston:
Intake port is tapered and rounded with as little metal removed as possible.
Sharp edges on intake and exhaust ports inside of liner are removed.
Piston is de-burred.
Piston and liner are hand fitted.

Rod: Oil holes drilled and polished

Crankshaft:
Crankshaft is reground to reduce vibration, Intake port windows is de-burred and blended. Crankshaft and case are fitted.

The Series 6 has weight added to the counter wieght on the Crankshaft
Counter weight is milled and filled with heavy metal.

Amen on the quality and manufacturing tolerances. I do think that in the past few years the overall quality has improved except for the P & C fit. I personally would like them a little tighter. The "no break-in required" fits are too loose. They are way too loose by the time you get the other parts heat-cycled enough to be broken in.
Ocassionally I still get one that seems that it cannot be made to run well no matter what I do to it. As you know, while I do EXTENSIVE work on the old Fox 35s, I do not do rework for the general modeling public. I leave that up to people like you and Lew and others. I do like to see what I can do to get a little more out of them.
Bigiron

PS I sent you a direct E Mail

>Marvin;
>What I have found and you most likely too over the years is
>there are so many variables in a Fox 35. The only constant
>is you well find huge differences in machine work and the
>ABC is down on power. There is no secret in making one run
>well, only patience. If someone reworks a few engines and
>they run good they consider themselves experts. When someone
>like you reworks hundreds of them successfully then I would
>consider them experts. The good thing is the Fox 35 will
>always lend a good discussion.
>Another thing for FYI is Randy Smith has just made 6
>replacement Crankshafts in which I have 3 coming. In talking
>to him he has corrected all the problems and covered all the
>mods that are now being done to the Fox crank. Just trying
>to figure out who I can get to test them for me, Don McCLave
>is top of the list.
>
>Larry

LARRY,
I fly with DON More then anyone. I'm building a Hi Johnson COUGAR and would LOVE TO TEST your engine. I rework my FOX. 35 and I like what I do to them. HOWEVER, I don't touch the crank. I do make sure that it's straight. E-mail me at [email protected].

Right now I'm averaging 15 engines (rebuilds and
>upgrades) a week and building for VSC, plus I'm still
>recovering from Back Surgery.
>Larry

Larry
Your customers appreciate your dedication and prompt turnaround. Thank you for setting the standard for the other engine builders!

Thanks for the kind words

A big THANK YOU to Larry as well. He did 2 of my motors at a special price. I have never met the guy, but I can tell you now he is my best pals. He went out of his way to do my motors and they are great! Ran one in my Skyray 35 and while it got too dark to do any real testing I am sure it is going to be my best Fox 35 yet. He engraves the crankcase so you never have to worry what motor is what. A real nice touch. His Hemi Head is like none other. I sure hope to do business again for my next Fox 35.
Jay

Thanks for the kind words

>Brodak .40 Stock 10X6 APC 41.6 10720 0.442
>OSLA .40 Stock 11X4 APC 47.2 10750 0.503
>OSLA .40 Reworked 11X4 APC 48.0 10900
>0.519
>OSLA .46 Stock 11.5X4 APC 57.6 12360 0.706
>OSLA .46 Reworked 11.5X4 APC 60.8 11644 0.702

Larry:

What mods are you doing to the LA engines?

Balance (newer engines can be made to run very smooth), de-burr(very little needed), redirect of the ports and blend the case to the full port configuration on the 46.

For those who are curious, Larry is correct in stating the ABC setups for the Fox 35 are very slightly soft in terms of power output.

I resisted this notion for several years, especially as I was flying a pretty light Smoothie and so didn't much care.

However, when beginning to use my 42-ounce Oriental, comparing it with those of Don McClave, my motor was a little soft. As it happened, about this time I owed Don a favor--few of us don't, what a generous guy he is--and assembled an ABC Fox 35 for him, beginning with a stock engine he furnished. Wanting an honest test I ran the engine in myself, even flew it a few times. Essentially a twin to the motor in my Oriental.

(While I am not sure this makes a big difference, I have absolutely no experience with Fox-produced ABC sets; I have only laid my hands on the pieces I was having made in Russia, that GMA sold on an exclusive basis.)

Don reported back that he liked the smooth nature of the engine, but that compared to the pieces he was getting from Larry Foster--hardly box-stock Fox 35s, I must point out--the motor I put together was just a little bit down on grunt, and here he held a thumb and forefinger closely together.

First, comparing well to Larry's Fox 35s is in itself a pretty good thing. And all of the ABC setups with which I have had experience easily out-pull all stock and owner-modified Fox 35s I have come across.

As to getting the power back, even going to the next step, nitro as been my answer. A 15/25/60 blend is used for most practice flying. For contests I like 20/25/55 and have been known to use 25/25/50.

Yes, there is a risk in running higher levels of nitro in a Fox 35, the most salient being that if you have a bad run and burn it down, it's toast and you can just toss that piston/cylinder in the garbage. Thankfully enough, this does not apply to my ABC sets in any way and so the risk is much reduced.

Further, the Russian-produced ABC sets have proven to have an extraordinarily long life. My high-time sets, even a couple which were intentionally brutalized during early testing, haven't lost a step.

Sometimes when Don and get together at a contest, he will mention that a particular motor has had a lot of running and has, or is about to, go over the hill. This has never been said as a whine, it's just a fact of life, one which eventually may even apply to my favorite ABC Fox 35s.

Not yet, however...

Well said Dan:
I agree on the life of the ABC, there's a guy here in Tucson that has burned down an ABC Fox I did for him twice now. I've replaced the crankshaft and case once and just the case the secound time. It still has the same ABC in it. I finally convinced him not to run APC11X5's and 10/25 in it.

I would also add Don McClave is, in my mind the authority on how to run a Fox.

Thanks, Larry. Currell

Well said Dan:
I agree on the life of the ABC, there's a guy here in Tucson that has burned down an ABC Fox I did for him twice now. I've replaced the crankshaft and case once and just the case the secound time. It still has the same ABC in it. I finally convinced him not to run APC11X5's and 10/25 in it.
I would also add Don McClave is, in my mind the authority on how to run a Fox.

Larry

Larry,

Knowing Don McClave well, another thread dealing with torque curves, dynos and such, at least in the case of the Fox 35, can be viewed as merely mental masturbation. I swear Don has the equivalent of a dyno--and a whole bunch more test equipment--in his right arm.

The only long-term problem I have had with ABC sets--other than seeing them out-last cranks and rods, not a bad thing--was in seeing a high-time set finally develop a real narrow needle setting. Don and I flew this engine in my Zilch X at the 2003 Roundup, and while it was fine in the air, hitting the needle ended up being a two-out-of-four deal with each of us getting one good run.

In fiddling with that motor a couple weeks ago I discovered that it was heavily varnished. Cleaning both piston and cylinder with 0000 steel wool brought it right back to having a broad needle. The power was the same, regarded as some sort of victory what with the impossibility in getting piston oriented *exactly* as it was to begin with, so I hope to see (slightly) improved power after some more running.

Compression is still quite good, not as good as when piston/cylinder set was in its prime, but it still hand-starts readily.

Dan - help! For the benefit of my Fox 35's soon to be put into service, what's the problem with an 11-5 on a Fox 35? I usually reckon you can "rule of thumb" some props when it comes to assessing suitability of props. I assume a 10-6 is just about the classic prop for a Fox 35, and a bit more dia and a bit less pitch (e.g. an 11-5) should end up with approx. the same loading?

Oh dear. Another oops. I see my message No. 38 should be addressed to Larry Foster. Dan - cancel my request please. Larry - look forward to reply. Best wishes, Ian. P.S. Of course my question really refers to std. Fox, not an L&J which I would never misuse!

Ian:
In my time playing with Fox and props, I've found that the larger DIA on the Fox 35 Loads it more and works the piss out of the front bushing causing it to over heat. I've also done Temperature testing on the bench and the 11X5 runs 16 to 22 Degrees (Deg F) hotter at the same RPM. It also takes longer to go back to a four cycle. I'll be running a bunch of engines after Thanksgiving and if I have time I'll give you torque specs on a 10X6 and 11X5
Larry

Fox 35 Larry's special with balanced crank flew on an profile Excalibur in Woodland CA this summer for 502 points. Pulled like a horse sounded very strong, was strong and pulled the plane with authority with a 10x5 full blade prop. Top flite I believe. Next contest with an OSLA25 with apc 9x4. Did well but not the same pull through the pattern. Fox did a better job. May be the prop but then the LA has difficulty with a 10x4 prop.

Bob Smiley
A Lancair 360 builder/flyer trying to be a modeler

Snip, snip...

I'll be running a bunch
>of engines after Thanksgiving and if I have time I'll give
>you torque specs on a 10X6 and 11X5
>Larry

Larry,

Ooops! Pretty sure I know what you meant to say; but it is still an "Ooops!"

Just had to get in here before that F4FGuy beat me to it.

Looking over your shoulder all the time,

>Snip, snip...
>
>I'll be running a bunch
>>of engines after Thanksgiving and if I have time I'll give
>>you torque specs on a 10X6 and 11X5
>>Larry
>
>
>Larry,
>
>Ooops! Pretty sure I know what you meant to say; but it is
>still an "Ooops!"
>
>Just had to get in here before that F4FGuy beat me to it.
>
>Looking over your shoulder all the time,
>
>Dan

Dan:
Not that you don't carry a lot of weight with me, sorry it took me 2 weeks to read your jab.

Larry
>

>>Snip, snip...
>>
>>I'll be running a bunch
>>>of engines after Thanksgiving and if I have time I'll give
>>>you torque specs on a 10X6 and 11X5
>>>Larry
>>
>>
>>Larry,
>>
>>Ooops! Pretty sure I know what you meant to say; but it is
>>still an "Ooops!"
>>
>>Just had to get in here before that F4FGuy beat me to it.
>>
>>Looking over your shoulder all the time,
>>
>>Dan
>
>Dan:
>Not that you don't carry a lot of weight with me, sorry it
>took me 2 weeks to read your jab.
>
>Larry
>>

Larry,

Have you been talking to Preston, or did you simply note his "expansive" comments which were directed my way?

"...carry a lot of weight with me," indeed.

No problem. You were included in my latest Bad Boy Stunt column, coming next month to a mail box near you. I think the comment to be hilariously funny even if target audience will prove to be rather narrow.

No hints, don't ask...

Dan:
No didn't read anything like that. The quote usally gets a response with guy's our age, so it makes it fun to use.