Author Topic: K&B 7.5 + pipe (Read 2951 times)

Michael Novobrantsev · « **on:** October 11, 2020, 11:09:28 AM »

Hello !
Do anybody have experience of use K&B 7.5 + pipe for cl stunt ?

Thanks

Brett Buck · « **Reply #1 on:** October 11, 2020, 02:15:46 PM »

Quote from: Michael Novobrantsev on October 11, 2020, 11:09:28 AM

Do anybody have experience of use K&B 7.5 + pipe for cl stunt ?

Tom Lay asked me about that, and I think he may have tried one, but no one appears to have had any success with it.

Brett

Air Ministry . · « **Reply #2 on:** October 11, 2020, 08:18:14 PM »

Ive got one with 190 exhaust timing , 110 trans. ! ( corrected . YES ! 190 ! Ex . ) just a trifle of overlap .

Sceptre Flight tests show other figures . As there were outboard & who knows what else .!

I think it was Lew woolard , at some time , did custom ' STUNT ' K & B ' SR II 's , with CUSTOM P/L assys .

So anyone out there with a F I R E SR II K & B set up for CONTROL LINE , has a iota of a chance it is a C / L stunt engine . though unlikely unless it is .

As youcansee , there a 20.000 rpm peak engine. Stock .Tho thats a 6.5 . 7.5 is similar .

Some of the 8011? ABC 40 parts interchange . Like rods maybe . These the R C & C/L arnt diferant internally . so both do for C/L .

There were a few differant rods in the SR II s as prolonged high rpm operation could throw early skinny ones .

Intresting, MY 7.5 came with a 6.5 head . And will chunter along slow & steady on a 11 x 7 !!!!!!!!!!!!
Though havnt done more than a few flight , so cant coment as to if it'd ' run away ' . But if it did youd think it'd be to olympic sprint standards .

My feory is the fuel / charge - up insideb the gap outside the chambers pulled down & feeds the second half of the downstroke .
Some vauge disimilarity to the bathtub lean burn tecnology, vaugely .

Brett Buck · « **Reply #3 on:** October 11, 2020, 08:38:35 PM »

Quote from: Air Ministry . on October 11, 2020, 08:18:14 PM

Ive got one with 160 exhaust timing , 110 trans. !

The 160 exhaust duration is probably not much problem, just make the pipe really long. I don't know for sure what you mean about the "110 trans" - if that means the intake port duration, then, that almost certainly will be an issue.

But the trump card for any such argument is that you know for sure a 40/40 VF works, a PA40/51/61/65/75 works, and a RO-Jett 61/67/76 works, and there are generally well-established systems, and in the case of the VFs or PAs, as long as you don't want a 75, there are hundreds of them rusting away in shoeboxes, and probably available for the asking.

Brett

Dan McEntee · « **Reply #4 on:** October 11, 2020, 09:39:06 PM »

You may know my flying buddy, Mark Hughes, from seeing him judge and fly at the NATS. Mark had a K&B .40 set up from Tom Lay when he first tried tuned pipes back then after crashing his really nice Jim Armour Epic. The model came out a bit heavy and performance was less than tantalizing, but after opening up the venturi .010" it got much better. Mark flew it in several contests as I recall and did OK with it, but crashed that model also. I would have to ask him if he still had the system. I'll just say it worked but it wasn't up to what the Vf.40 was, and Mark moved on to PA engines. If a model was sized for it and weighed an appropriate weight, I would think it would be at a minimum usable if that was all you had.
Type at you later,
Dan McEntee

Brett Buck · « **Reply #5 on:** October 11, 2020, 10:09:23 PM »

Quote from: Dan McEntee on October 11, 2020, 09:39:06 PM

You may know my flying buddy, Mark Hughes, from seeing him judge and fly at the NATS. Mark had a K&B .40 set up from Tom Lay when he first tried tuned pipes back then after crashing his really nice Jim Armour Epic. The model came out a bit heavy and performance was less than tantalizing, but after opening up the venturi .010" it got much better. Mark flew it in several contests as I recall and did OK with it, but crashed that model also. I would have to ask him if he still had the system. I'll just say it worked but it wasn't up to what the Vf.40 was, and Mark moved on to PA engines. If a model was sized for it and weighed an appropriate weight, I would think it would be at a minimum usable if that was all you had.
Type at you later,
Dan McEntee

Early-mid 90's? That may have been the same engine, or based on the conversation I had with him.

Most memorable moment was that was the day I met Bob Palmer.

Brett

John Leidle · « **Reply #6 on:** October 11, 2020, 10:15:35 PM »

Mark Hughes & I both bought one of Tom Lay's T&L .40s it was a engine like pictured here with Tom's replacement piston liner at least I think he replace the piston & matched the set I know the liner was a replacement . Very high timed the exhaust timing was over 165 degrees if I remember back 23 years , The ports were quite large set it up as directed & it ran crappy to say the least so I applied the exhaust timing to an equation & ended up with a pipe length much longer than suggested. It improved but eventually gave it to a guy in Idaho plugged an OPS.40 SPA into the plane & my troubles were only a memory.
How a stock K&B would run is a mystery ... other proven options in the .40 size unless you want to fiddle & experiment. Powerwise the OPS would eat it alive. According to Mark his wasn't great either.
John L.

Reptoid · « **Reply #7 on:** October 12, 2020, 12:23:40 AM »

The K & B 6.5cc (.40) and the 7.5cc (.45) are two completely different animals. The 6.5cc came in several timing variations; std., pylon racing (AMA & FAI), and speed. The Rpm peaks are vastly different on them. Both exhaust and bypass timing are different. Exhaust timing varied from 150 to 180+. (crank timing is also different for the speed version. The FAI version is timed for a full high RPM pipe and FAI fuel (No Nitro)
The 7.5 came in even more variations; std.RC, ducted fan (the engine in the picture posted by the OP), Inboard marine, outboard marine. Again, timing is vastly different. In addition, the outboard engine has a "left hand" crank because the power take off is in the (traditionally)rear cover.
An engine timed for inboard/outboard marine or Pylon racing is timed to run at 20,000 to 30,000+ (Cylinder and crankshaft). It will not run well in any reasonable RPM range for stunt even with a long pipe because it will make very poor torque and have terrible fuel draw at the lower RPMS.

Michael Novobrantsev · « **Reply #8 on:** October 12, 2020, 03:04:01 AM »

i Think , if timing period k&B will make (cylinder lower ) to 144/122 so as Os max 40/46vf , style of working of k&B will be similar os vf , or not ?

Air Ministry . · « **Reply #9 on:** October 12, 2020, 08:27:50 PM »

Quote from: Brett Buck on October 11, 2020, 08:38:35 PM

The 160 exhaust duration is probably not much problem, just make the pipe really long. I don't know for sure what you mean about the "110 trans" - if that means the intake port duration, then, that almost certainly will be an issue.

But the trump card for any such argument is that you know for sure a 40/40 VF works, a PA40/51/61/65/75 works, and a RO-Jett 61/67/76 works, and there are generally well-established systems, and in the case of the VFs or PAs, as long as you don't want a 75, there are hundreds of them rusting away in shoeboxes, and probably available for the asking.

Brett

Thats a TYPO ! . had the info out last night, but didnt find the written down timing figures .

It actually 190 / 110 . ! and tho I didnt remeasure it Im sure thats correct .
The crank timings real weird too . Narrow i think , but as the ports about 6 feet wide , it'd even out .

I got it ' as supplied ' by a speed freak . so assume it was the reject ' Non - Suitable ' for mega rpm parts thrown together .

The liners look to be ported after chromeing . Maybe Woolard got un cut port liners from K&B . And the thing I saw refered to the 6.5 F I R E SR II ' stunt ' .

Maybe the shaft was sleeved too , as the passage is rather generous .

Micheal ,
Youd probly be better using ' something else ' . Though If you want another one , a good Talka 7 & muffler would be a trade .

Theres a S Tigre X 45 , silver head . Dykes Ring A B C . mine measures 140 / 120 ' off the shelf . Just a notch lower than the VFs .
Tho apparently the blue head ones are higher timed .

The OS SX / AX look like they may be ( slightly ) VF related , 6 bolt heads . Maybe 16 mm shafts . the 50 is L S , 22 x 21.5 . tho thats still the usual ' undersquare ' .

Some drivle on SR's here https://www.rcuniverse.com/forum/glow-engines-114/5364485-k-b-45-pylon-df-2.html

GERALD WIMMER · « **Reply #10 on:** October 13, 2020, 04:27:31 AM »

Hello It was a long time ago (+30yrs) brought a new K&B6.5 aero RC engine from Steves Model Panmure Auckland and used it with the traverse mounted stock muffler on a large profile stunter with the wrong sized stunt props and found it wanted smaller props that could not pull the plane effectively.
I did not de-pitch to say an 11x4 or use a pipe like I would if doing it now. Swapped it out for a H.P. 40 RE which ran very well even as a rear induction engine but then swapped to a basic Fox 60 Eagle (early baffle engine) which ran much better and is still on the same model now but it is very old (ugly) an oil soaked.
Regards Gerald

Michael Novobrantsev · « **Reply #11 on:** October 13, 2020, 07:01:29 AM »

I was read and think.
My conclusion: for c / l stunt for piping working better ordinary schnuerle muffler (rc) engine vs exactly piped high rorotary engine! ??
I already buy on ebay NIB K & B7.5 engine (50 $)
I will try chnage timing on them to 144ex 122tr 200ind and do experiments with pipe
I have several good working classic engines (enya 6001, como.51, st. 46, fox eagle 60) for my everyday training.
I want to take experience with piped engine no spending money.
I have idea , sleeve goes lower to144ex 122tr and formed crank window so as 45degree --- to 245degree ind period.
I see cylinder head goes deep enough in sleeve, so after lower sleeve i can upper head by gaskets.

Brett Buck · « **Reply #12 on:** October 13, 2020, 10:26:51 AM »

Quote from: Michael Novobrantsev on October 13, 2020, 07:01:29 AM

I was read and think.
My conclusion: for c / l stunt for piping working better ordinary schnuerle muffler (rc) engine vs exactly piped high rorotary engine! ?

Of course you can do as you wish, but I would never, ever, suggest modifying an engine of unknown capability when far better alternatives already exist. No one needs a modified engine.

My advice - which you are free to follow or ignore- is sell it or trade it for a 40 or 46VF, PA51/62/65, or a RO-Jett PA61 BSE. Of course you use these with a tuned pipe, since that has been the only competitive IC system for 30+ years or so, with very rare exceptions.

Brett

Michael Novobrantsev · « **Reply #13 on:** October 13, 2020, 11:44:24 AM »

ok!
Thanks.

Air Ministry . · « **Reply #14 on:** October 13, 2020, 09:43:32 PM »

OOPSIE . Oh Well , whats ten degrees , between friends. Anyway .

Thought Id better check the Exhaust timing , as you can see it o.k. , assembled . 170 degrees . Which Agrees with Mr CHINN . ( anylisis )

Then thought maybe Id better check the induction , seeing I had it out . ! I.O. 40 - I.C. 50 . Mr CHINN had nothing to say on the induction timing . Outboard or D.F.

As the head bolts wernt nipped up , I then thought Id better check the Transfer timing too , . . . Side Ports 114 duration , front ports 110 ditto . Mr CHINN believes 122 & 120 apparently .

Theres a few series of these , He states the Outboard has the ' non pipe ' timing standard . Tho says " slightly lower " .

Case intake is 16 m.m. / 5/8 " bore . With 11 m.m. across the induction passage at the crank .

We'll see how the ikle pretty photos transpire . . . . Hold your seats .

Top of exhaust port is LEVEL with the case Ex. port face .

Air Ministry . · « **Reply #15 on:** October 13, 2020, 09:47:56 PM »

Further wonders of modern science .

Hard to tell if the fine swirl in the combustion chamber is machineing marks or high tech swirl technology . Maybe both , actually .

Bore and Liner are imperial dimns. so metric stuff wont be a ' drop in ' .

Mine , the heads ).8 mm smaller diameter -> O.D. - to liner . Claerance to piston T D C is maybe 0.65 mm . So C:R is about half that of stock . Seems to hold low rpm o.k. with a vertical toungue muffler
from a squashed 3/4 in. dia tube about 1 1/2 long . six 3/32 holes up across ( 2 fwd 4 aft ) to feed into chamber to scaleish ex out in fuse .

Air Ministry . · « **Reply #16 on:** October 13, 2020, 09:53:16 PM »

Quote

I have idea , sleeve goes lower to144ex 122tr and formed crank window so as 45degree --- to 245degree ind period.

You start doing this , and SUB PISTON INDUCTION starts showing up .
Some engines like 45 FSRs youll only drop the sleeve 8 thou. before it opens under the piston at T D C .

So START at finding window exposure under piston .

140 / 120 'd be o.k. maybe . If piston hight works .

Michael Novobrantsev · « **Reply #17 on:** October 14, 2020, 04:39:33 AM »

Ок !
Thanks Now i will wait my purchase . when i receive engine i check it timings .

Michael Novobrantsev · « **Reply #18 on:** November 04, 2020, 11:01:40 AM »

" My advice - which you are free to follow or ignore- is sell it or trade it for a 40 or 46VF, PA51/62/65, or a RO-Jett PA61 BSE."

I sold engine . Its timing : trans-122 , ex-178 , crank induction 187. Weight 315 gr .

I need trying to use como 51 sch withpipe

What do you think about pipe for this engine ?

GERALD WIMMER · « **Reply #19 on:** November 04, 2020, 02:39:46 PM »

Hello
The Como 51 C/L schnuerle ported engine is in fact the test subject of Mike Billinton's engine review for control line stunt see:
http://sceptreflight.com/Model%20Engine%20Tests/Como%2051.html
It was interesting as he indicated the engine should work well with a tuned pipe after experimenting with the correct length/rpm range

Regards Gerald

Brett Buck · « **Reply #20 on:** November 04, 2020, 04:13:34 PM »

Quote from: Michael Novobrantsev on November 04, 2020, 11:01:40 AM

I need trying to use como 51 sch withpipe

What do you think about pipe for this engine ?

I know absolutely nothing about it, I didn't even know Como was still making engines into the schneurle era.

Brett

Air Ministry . · « **Reply #21 on:** November 05, 2020, 10:19:52 PM »

Think it'd be related to these ' S ' series S T's ( same era ) and similar to G 51 . Has the same bearings but a shorter C shaft . G 51 same bore & stroke . So maybe liner interchanges .
Were a RINGED & a ABC in the Como Schneurle.

The Baffle piston pdp Como is a V Good injun . Smaller ' K ' ( last series ) V 60 . or a super .46 . ( Youd get changeing 51 & 40 como parts ) Mounts same as G 51 but shorter ( 5 or 6 mm ) nose .

RandySmith · « **Reply #22 on:** November 05, 2020, 11:09:27 PM »

I still have a couple of the COMO 51s with baffled ring setup, I used them in the late 80s early 90s, Great engines
The have very good power and run just like a ST 60, but more fuel efficient because of tall baffle. I used one in a Magnum and Flew a Vector with them
The ABC loop charged version did not work as well. That does not mean you could not get it to run well on a pipe setup though. That I did not try.

Randy