Brodak 25

[Zuriel Armstrong]

After reading the Jetco Dolphin thread I was wondering if a Brodak 25 would be enough for a mid 30oz Dolphin or similar plane.  I have flown mine on a light Ringmaster but do not have anything else to compare it to.

[Robert Zambelli]

Zuriel - It can handle a 30 ounce plane with no probelm. The ARF Cardinette weighs just about that and the B-25 flies it with no effort.

Something to consider, however is that the Dolphin has a bit more wing area than the Cardinette and therefore more drag to overcome.

Keep in mind that (stunt) performance is greatly improved with a head modification. I have done several and it really makes a difference.

Let us know how it performs.

Bob Z.

[Steve Helmick]

I think the B.25 would be perfect for the full fuselage version of GMA's "Peacemaker", FWIW.  Steve

[Chad Hill]

Speaking of the B25, I understand that there is no bushing for the crankshaft. If the props are kept balanced what kind of life-expectancy is there before too much fuel begins leaking out the front end of the case? Anybody have experience to share here?

[Joe Gilbert]

Chad I have had mine on a Ringmaster that has been flown for three contest seasions and is still a great engine. No trouble at all 9x5 APC at 9600-9700  four stroking at take off.

[Alan Hahn]

Speaking of the B25, I understand that there is no bushing for the crankshaft. If the props are kept balanced what kind of life-expectancy is there before too much fuel begins leaking out the front end of the case? Anybody have experience to share here?

Chad,
Why would you say that?

My B25 has a bushing on it.

[Allan Perret]

Keep in mind that (stunt) performance is greatly improved with a head modification. I have done several and it really makes a difference.
Bob Z.

What mod do you do to the head, and how does it change the stunt performance ?
Mine runs pretty good stock..

[Chad Hill]

Alan, I looked at a used case. Looks like machined aluminum inside where the shaft spins. I took a magnifying lense and could see no evidence of any bushing pressed in. Some of the old single BB Fox 36Xs were like that, too.

[Alan Hahn]

Chad,
Mine has a nice brassy (or bronze) look, just inset inside the crankcase front end. Also had to use my magnifying goggles to see it (old eyes aren't good enough anymore). But I did take a look last night.

So it looks like a bushing to me. I am too lazy to remove the crankshaft (and cylinder/piston).

I suppose we could wait until some other "authority" might respond. I believe mine was from the second round of engines---but I am not really positive about that. So maybe there are different versions out there. Or I could be delusional!

Some of the early K&B' Sportster Series engines used the high silicon aluminum of the crankcase to be the bearing material. Later they went to a bushing. Not sure if it was because the aluminum failed (not enough oil in RC fuel?) or marketing.

[Chad Hill]

I'm puzzled too, Alan. I went and checked the case again. I even looked thru the venturi housing, as well as from inside the case. I don't see any signs of a pressed bushing. Anybody have input?

[Bob Reeves]

It isn't pressed in, It's put in during the casting process and you probably can't see it without removing the crank.

[Chad Hill]

Well, I did have the crank out...it's just a case. Aluminum colored, inside and out.

BTW, the B25 weighs almost an ounce lighter than the LA25. If there is no bushing, and since the B25 is AAC while the LA25 is ABN, that could account for the difference in weight--

[Zuriel Armstrong]

Zuriel - It can handle a 30 ounce plane with no probelm. The ARF Cardinette weighs just about that and the B-25 flies it with no effort.

Something to consider, however is that the Dolphin has a bit more wing area than the Cardinette and therefore more drag to overcome.

Keep in mind that (stunt) performance is greatly improved with a head modification. I have done several and it really makes a difference.

Let us know how it performs.

Bob Z.

Bob,

Thanks for the reply.  Does the head mod change the run characteristics or the ability to haul around a larger plane?

[Garf]

My Brodak 25 is starting to develop some slop in the rod. It still runs great, but i'm getting concerned.

[Paul Taylor]

Bob,

Thanks for the reply.  Does the head mod change the run characteristics or the ability to haul around a larger plane?

ZMan,
You are not looking to put this on your new plane?

[Chad Hill]

Garf,

FYI I bought a used B25 from a friend who had crashed it and damaged the case. I took the innerds apart and put them in a new case. The rod is bushed for the crankshaft pin, and the bushing, though it still fit tightly inside the rod and around the pin, had rotated about 30 degrees inside the rod so that the bushing/rod oil holes did not line up. I drilled a new oil hole and tried to move the bushing around inside. It was still smug so I gave it a try and have had no trouble for 15-20 flights.

The friend had been using the motor for SL combat with 8" props, but I have read that Aussies use it for speed and they haven't reported any probs, so not sure if higher rpms harmed it.

It's a great little motor with lotsa power, and a blast to fly on an F2D.

[Lyle Spiegel]

If you still have the old case I would be interested to evaluate it- I would X section it and then polish and etch to reveal the Alum casting and confirm  a bronze bushing.

[john e. holliday]

The rebuilt Brodak .25's are the engine of choice for B -Team racing in their country.  Would love to get one of their set ups.  The B 25's I have are great runners and the one the grandaughter uses is a fuel miser.  Goes forever on one ounce of fuel. 

[Chad Hill]

Hey guys, I e-mailed John Brodak about the bushing question. Will let you know when I hear from him.

[Robert Zambelli]

Zuriel asked:  "Bob, Thanks for the reply.  Does the head mod change the run characteristics or the ability to haul around a larger plane?"

Zuriel - Sorry I cannot answer that because the only plane I've used it on is the Cardinette.

The main reason for the head mod is that the engine would often lock into a lean run and stay there. With the mod, it would change nicely form 4 to 2 and back. It worked nicely when loaded with a 9-6 Master but was a bit fast.  We will try it with a 9-5.

Paul asked: "Z-Man, You are not looking to put this on your new plane?"

Paul - no, the new plane will fly with a SAITO 30.

Bob Z.

[Chad Hill]

I received a reply today from Tom Hampshire, on behalf of John Brodak. I had e-mailed John about the B25 bushing.

"Hi Chad-It's an aluminum bushing, cast in place when the crankcase is molded.  Tom Hampshire"

[Alan Hahn]

I received a reply today from Tom Hampshire, on behalf of John Brodak. I had e-mailed John about the B25 bushing.

"Hi Chad-It's an aluminum bushing, cast in place when the crankcase is molded.  Tom Hampshire"

Well I guess I'm delusional, mine really had a brass shine--maybe it is a little congealed castor.

[Dick Pacini]

Well I guess I'm delusional, mine really had a brass shine--maybe it is a little congealed castor.

It is probably an Aluminum Bronze alloy sleeve bearing which would show a yellowish hue when worn a bit. 

I don't believe a pure aluminum bearing would last any time at all.  If the bushing is aluminum as is the crankcase, it wouldn't make any sense to have a bearing at all.

[Alan Hahn]

It is probably an Aluminum Bronze alloy sleeve bearing which would show a yellowish hue when worn a bit. 

I don't believe a pure aluminum bearing would last any time at all.  If the bushing is aluminum as is the crankcase, it wouldn't make any sense to have a bearing at all.

There apparently are some silicon-aluminum alloys that are purported to be pretty good as bearings. At least that was what was claimed!.

In my case, I was only looking at the bearing exposure at the front of the crankcase (I took off the thrust washer). It definitely looked like a different structure than the aluminum of the crankcase. So I was seeing the front edge. Could have been old castor giving it a golden hue I guess --or you could be right about the alloy.

I wonder if the Brodak 40 has the same bearing material?

[Bill Little]

After reading the Jetco Dolphin thread I was wondering if a Brodak 25 would be enough for a mid 30oz Dolphin or similar plane.  I have flown mine on a light Ringmaster but do not have anything else to compare it to.

HI Z-Man,

When the B-25 was being developed, I spoke several times with Tom H.  We discussed the similarities with it and the old '57 Fox 25 (a mini Fox 35 in a .19 case!).  Tom was very familiar with the Fox and his impressions were that the B-25 was stronger, but had much the same run characteristics (like a Fox 35).  So I would have no problem in using one in a Dolphin that was around 28-32 oz.   I understand the B-25 with also run a higher rpm/lower pitch set up, also.

Big Bear

[Zuriel Armstrong]

Hi Bill,

That is what I wanted to know.  I want a fun airplane for fair weather flying.  I think the little B25 would do nicely and I do not intend to use much color or added weight.  i have a Dolphin kit that needs to be built...like everything else in myshop!!! 

Thanks for the response.

Zuriel