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Engine basics => Engine set up tips => Topic started by: Charles Carter on May 30, 2015, 10:25:06 PM
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Who can rework a stock crank and change the timing for reverse rotation? I have a twin pathfinder and I am interested in both props rotate towards the canopy. Engines are OS Max 25 LA's.
Charles Carter
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Perhaps a gearbox would be the only solution here.
The only other ways are to find someone to make a new crank or remount the whole venturi intake 90 degrees clockwise (like some Enyas are able to do with their rotatable front housings).
No solution is going to be easy and good luck trying to find someone that doesn't consider this a waste of time.
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Back Around 60 ' ya got whole cranks that were a tangle of welds , stroked Olds and the like ,
(http://image.superstreetonline.com/f/9064823+w660+h440+q80+re0+cr1/0610turp_12z%2Bcastillo_crankshaft%2Bwelds.jpg)
and it was sttandard to fit a Ford 221 steel crank to a stroked Holden , either the flywheel end was built up from weld & machined ,
or usually a end of a steel Holden Crank was grafted on & welded .
So its not imposable , though youd need someone with their Eye In & set up for it . A real welder like there used to be , cut & weld
or rebuild & machine web / pin . Though it'd be a bit finikey & as easy ( if you were set up for it :##) to make a new crank . :-[
Wonder how far of a Enya Crank is ?? . You could always put Enyas in it . ~^
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Wonder how far of a Enya Crank is ??
It is not any crank difference that enables the Enyas to run the in the opposite direction, it is the ability to rotate the front casting in 90 degree increments.
I believe that a negative 90 degree turn will enable the engine to run backwards very successfully due to its even 180 intake timing.
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Unless you put Enyas LEFT HAND CRANKS in them .
then you could rotate the front housing and run it clockwise ! :##
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(http://www.roi-import.com/catalog/images/TH27402000.jpg)
If you were real lucky you could drill the cheek on the reciprical , and press in a steel bearing roller for a crankpin .
Weld to build up check and grind to match balance . Tecnically its no probllem to weld !
if you know the steel type , deharden , imerse in argon to weld , grind , reharden the finish ! :## n~
If theres a ' good old boy ' engine shop around , ( hot rod race engines ) they might take on a weeny thing like that .
Its fairly common to weld crankpins in ring dings , porshes , and other rubbish like that .
(https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQdtmUTXj8clWPDqrJGr7eylAnL-yZvSEOEWIY1ZJCBL6YKAVZA)
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My aproach would be to block the venturi hole & shaft bore, and make a rear intake backplate. Thats, if I had to do it. L
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I think the best way to "rework" the crank would be to set it it on your lathe for reference, then make an entirely new one. Someone who can do the precision grinding for the bearings, or is willing to lap the crank to size, could do it fairly easily. Getting the two motors to match exactly in performance would be challenging.
I think the best way to solve your problem is to go electric.
Gearboxes for IC engines are finicky things, and no one is making them. It'd be more work to make one than to make a new crank from billet, and when you're done it'll be fragile and heavy.
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there is one way to do it ,, it would take two cranks turn the complete crank web off the crank .take the 2nd crank and chuck it up and bore it out to about .002 under the size of the other crank stub , set up a jig to keep it alined where u want it, . put the crankshaft in the freezer for about 1/2 hr heat up the web and press together .when done u could silver braze it to have a better safty factor , or if u know a good heliarc welder he could run a small bead around the outer edge . what is it going to be used for ???
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Or you could just run one engine as a pusher.
Matt, good luck buying an Enya engine let alone a lefty crankshaft these days!
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Who can rework a stock crank and change the timing for reverse rotation? I have a twin pathfinder and I am interested in both props rotate towards the canopy. Engines are OS Max 25 LA's.
Charles Carter
Use Enya's, you can get reverse cranks for either their 20 or the 25. I have a matched pair of each. Also plan to build a Twin Pathfinder some day.
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Or you could just run one engine as a pusher.
Matt, good luck buying an Enya engine let alone a lefty crankshaft these days!
I bought the matched set of 25's from Enya several years ago when they did a limited run. But recently (2-3months ago) bought a reverse crank for one of my two 20's to have a set of those also.. I would bet you can still get reverse cranks for either. Send Ken Enya email. Address is on website.
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For engines with a case front venturi you need a reverse crankshaft, there are some engine manufactures that have reverse cranks available (there was a reverse crank offered by Fox for the 35Stunt). The easiest is a reedvalve engine (i.e. the Cox 15) runs either way just fine. The next is an engine with a rear intake, these just need to rotate the backplate from the top right side to the bottom left side (looking at the back of the engine).
Actually, the easiest thing for twins would be electric were you just change any two motor wires and it reverses rotation direction.
Best, DennisT
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Many years ago, I was toying with the idea of building a BD-5 stunter. The BD-5 uses a pusher engine on the rear of the fuselage.
I was going to use an OS Max 35S, so I wrote to OS in Japan and they sent me a reverse rotation crank. I never followed through on the project. OS billed me a very reasonable price for the crankshaft. In 2004, I moved and ended up tossing it.
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Do model electric engines have any advance on their commutator?
If they do then simply reversing the wiring will reverse the advance and kill off a lot of power in the bargain.
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Do model electric engines have any advance on their commutator?
If they do then simply reversing the wiring will reverse the advance and kill off a lot of power in the bargain.
Soooo, you went bowling with a bunch of short guys, and you just woke up, and...
Serious model electric motors have been brushless for at least a decade. No brushes, no commutators -- the ESC has three power wires, and the commutation is done in the ESC.
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Soooo, you went bowling with a bunch of short guys, and you just woke up, and...
Serious model electric motors have been brushless for at least a decade. No brushes, no commutators -- the ESC has three power wires, and the commutation is done in the ESC.
Wonder where that beard came from!
Thanks Tim.
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Just checked the Plettenburg site and they still make at least 60 types of brushed electric engines that look serious and are designed for rc use....hmm.
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there is one way to do it ,, it would take two cranks turn the complete crank web off the crank .take the 2nd crank and chuck it up and bore it out to about .002 under the size of the other crank stub , set up a jig to keep it alined where u want it, . put the crankshaft in the freezer for about 1/2 hr heat up the web and press together .when done u could silver braze it to have a better safty factor , or if u know a good heliarc welder he could run a small bead around the outer edge . what is it going to be used for ???
Just As I thought !
except you could use CO2 or something really scary , to freeze the crank . Liquid Nitrogen ?? ;D
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Many years ago, I was toying with the idea of building a BD-5 stunter. The BD-5 uses a pusher engine on the rear of the fuselage.
I was going to use an OS Max 35S, so I wrote to OS in Japan and they sent me a reverse rotation crank. I never followed through on the project. OS billed me a very reasonable price for the crankshaft. In 2004, I moved and ended up tossing it.
You Know What Happened to the Last Person Who Did That ! . :X %^@ S?P
Sounds like OS is going to be getting a few enquireies regarding L. H. Cranks .
Got a few Veco 19 BB ones . 20 , 25 & 35 ones would do the trick though .
Only Delema is , which do you do what way on a FOUR Engined contraption . :P
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Only Delema is , which do you do what way on a FOUR Engined contraption . :P
PW used standard cranks in the .15FP's in both his B-17 stunters, usually turning 9-4 or 9-5 APC's, but huge venturi bore and pressure fuel system. It worked fine, but he did find out that it wasn't a good idea to try taking it off with only the outboard 3 engines running. :X Steve
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(http://www.roi-import.com/catalog/images/TH27402000.jpg)
If you were real lucky you could drill the cheek on the reciprical , and press in a steel bearing roller for a crankpin .
Weld to build up check and grind to match balance . Tecnically its no probllem to weld !
if you know the steel type , deharden , imerse in argon to weld , grind , reharden the finish ! :## n~
If theres a ' good old boy ' engine shop around , ( hot rod race engines ) they might take on a weeny thing like that .
Its fairly common to weld crankpins in ring dings , porshes , and other rubbish like that .
if u look real close ,one of the welds on the crank pin is cracked right through the middle of the weld ( bottom one )
(https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQdtmUTXj8clWPDqrJGr7eylAnL-yZvSEOEWIY1ZJCBL6YKAVZA)
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Braze a plug in the intake window then cut a new window.
MM