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Old Aug 21, 2010, 04:23 AM
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Bradles's Avatar
Australia, VIC, Sunshine West
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HELP "flex shaft assembly"

got a couple of stupid questions, but how do i actually assemble everything.

here is an example pic, do i just slide everything together?? do i need to seal anything?? does water go up the shaft? do i need to lube shaft when using Teflon insert? what size shim do i put in between the prop collar and strut, as shown in pic??

so hard to find info on this topic.
if you guys can help a beginner out, will be gladly appreciated.

thanks


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Old Aug 21, 2010, 04:30 AM
nick 30
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1 - yes you lube the shaft with flex shaft grease (i do it every 3 runs)
2- leave a 4mm gap between the drive dog (the forked thing) and the strut
3 - the brass tube slides into the strut then the shaft slides through the strut and tube
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Old Aug 21, 2010, 04:39 AM
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thanks nick

so a 4mm gap, not sure if i have enough shaft to leave that sort of space maybe 1or 2mm. would a bit of graphite grease work for lube, as alternative? or some lubricant spray?
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Old Aug 21, 2010, 05:36 AM
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You need the space between the drive dog and strut because the cable will shorten up as it twists from the torque of the motor. Without a space there you will damage the strut and possibly the motor bearings as the drive shaft will be pulling the motor shaft into the front of the motor, it wouldn't have a thrust bearing to take this load.
Use a good waterproof marine grease, I used to use some that came in a kilo tub from the autoparts store. Now I'm using park bicycle grease! less than 7$ for a 500g tub. Waterproof, safe for all plastic, good consistency, not too thick or thin. Looks a lot like grimracer cable grease!
I personally have never used the teflon liner, almost used one once but it felt like there is more drag in the teflon tube vs. the cable running in the brass.
Been using flex cable that way since the 80's when people started using flex!
I always pull it out of the boat at the end of the day, clean it with wd40, re grease it put it in a baggie and leave it out of the boat. It will rust if you don't lube it up at the end of running.
This also forces me to go over the boat again before running it, check for loose screws etc.
Also that propnut is no good! It will fall off and you will lose the prop! Get a nylon lock nut for it. I have no idea why octura still sells them, probably so you have to buy more props! Save that one for display purposes only!
I also grind a small flat on the stub shaft for the drive dog set screw to "bite" into.
With the cable greased you shouldn't get more than a couple of drops of water in the hull, the twist in the cable should force it out of the boat. A small piece of fuel line or shrink wrap over the end of the stuffing tube in the boat can act as a seal, have it half on the stuffing tube half over the flex cable.
I always also put a small chunk of sponge in the radio box and motor compartment to absorb any small drips that get in the boat.
You bought the assembled flex cable right? So no questions on assembling the stub to cable?
Hmm just got thinking about something new to post!
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Old Aug 21, 2010, 06:00 AM
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Quote:
You bought the assembled flex cable right? So no questions on assembling the stub to cable?
what i got was the brass tube, teflon liner, flex shaft, and prop shaft. everything was separate. so im guessing not.
the flex shaft slots into the groove(back of the shaft)

Quote:
You need the space between the drive dog and strut because the cable will shorten up as it twists from the torque of the motor
will try and get the most space i can.

Quote:
Also that propnut is no good! It will fall off and you will lose the prop! Get a nylon lock nut for it
that pic was an example, was easier than me taking a photo of my stuff, as i actually has a nylon nut on my setup.


thanks for the info siberianhusky
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Old Aug 21, 2010, 07:38 AM
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If its a seperate prop stub shaft, then you dont need the gap.....i cant tell from the pics, but if it is, it thrusts on the washer, if it is solid then you need the gap.
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Old Aug 21, 2010, 07:46 AM
nick 30
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i put thrust washers on all my motors, instead of the bearings inside the can getting the full force, the thrust washer transmits it to the can kind of like the down cables on a suspension bridge, transmits the load all along the lentgh and into the ground
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Old Aug 21, 2010, 08:29 AM
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Wow, this thread is a life saver.

I disassembled my drive shaft in the process of doing upgrades, as suggested by you guys, and did not pay attention to the 4mm gap between the strut and dog (the dog has a set screw that allows you to leave the gap). So I would have wondered why I had so much drive shaft threads sticking out behind the prop nut

It really pays to read every thread and post in these boat forums.

This stuff is more complicated than airplanes

Thanks,

Thomas
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Old Aug 21, 2010, 08:32 AM
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Quote:
Originally Posted by nick30head View Post
i put thrust washers on all my motors, instead of the bearings inside the can getting the full force, the thrust washer transmits it to the can kind of like the down cables on a suspension bridge, transmits the load all along the lentgh and into the ground
Can you please show a picture and/or give me a better explanation
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Old Aug 21, 2010, 08:37 AM
nick 30
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a thrust washer is comprised of 3 parts, 2 metal rings with a grove in each one and a plate with ball bearings, this goes bewteen the motor and coupler, it butts up between them both
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Old Aug 21, 2010, 08:52 AM
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assembly

Chuck the factory prop nut. I have found it to be out of balance, get a 540 nut if cable is .130 and the Gentleman from Canada says nylon nut, he's correct. Now from picture, cable looks bigger than a .130 cable. I have a question on brass tubing; what size is it and what size is teflon liner. The liner should be a tight fit in brass tubing. Now if is a hair to big -teflon- just use sandpaper to sand liner till it slides in snuggly. I have to do this with .130 liner and 7/32 brass tubing. Guys laugh at me when i say i sand flex cable down till shiny to reduce friction in liner. Andy Kunz uses Wahl barber oil for clippers for lube in stuffing tube. I use teflon grease, light coat, every run. Reason i use .130 liner in 7/32 brass tubing is to keep water from coming up the stuffing tube. Here's another tip, file the dog drive front face that is next to stuffing tibe if bigger than stuffing tube. Now if bigger, it can force water up the tube cause it catches water and also causes drag. Now if you don't want to sand the whole flex, sand where flex makes a bent in tubing. No strenght is lost what so ever. No need to reply! I don't use thrust washers, i just leave 2-3 mm space at drive dog. Flex shaft is where grease is super important due to components in strut shaft.-----Forgot, i use brass tubing but doublewall it for the strut. I then get nylon curtain pullers and drill out so flex shaft runs smooth . The curtain pullers are 1" long and are hollow and slide right in and are held wth CA. This takes time but is alot less weight. I picked up alot of tips from Earny Lazenbury of U.K. who used to write for the MMI of U.K. I was reading Pauls posting on liner. You could do this; use a piece of liner in stuffing tube about 1" long and slide it in so it starts at trasnsom and pushed in the 1" toward the bow should do the job.
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Old Aug 21, 2010, 10:11 AM
RELAX. You'll live longer
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Everything retoabcr said is spot on. But here's a couple of tips.
If the teflon tubing is a bit tight, instead of sanding it, I hold one end in the vice, grab the other end with some pliers & stretch it a bit. quickly cut off one of the squished ends & slide it up the stuffing tube. It will expand into place. Then trim off the ends to the length required.
After sanding the flex cable (I use some 400 paper) spray with WD40 & wipe clean to remove all the particles from the grooves, then grease before sliding it into the tube.
But the last couple of boats I've set up I used a smaller brass stuffing tube with no teflon liner. Just running the flex in the brass tube. Much less friction.
In the gap between the drive dog I add a thin piece of silicon water cooling tubing (about 3/4 of the length of the gap) to stop the water being forced up the bearings. Sort of like an O ring.
There's plenty of give in the tubing if the flex winds up a bit. Works a treat.
But I do use a thrust bearing on the motor to save the end bell bearings on the motor though.

I think you might need to follow this tip to assemble your flex shaft. It's how I do it.

http://www.offshoreelectrics.com/inf...mble-shaft.php

Cheers.
Paul.
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Old Aug 22, 2010, 02:48 AM
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ill have to take some pics, so i can make sure that what ive got is assembled right, will try and get this done tomorrow. as run out of time today.

hey nick, so if i read your post right, you replace the outer motor bearing with a thrust bearing. that's quite interesting. have you got any pics of that? to share.
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Old Aug 22, 2010, 03:21 AM
nick 30
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no you don't replace the motor bearing (until its knackered) you just add the thrust bearing, the inner diameter (ID) of the thrust bearing has to be the same as the shaft diameter

the photo's should help (illustration purpose's with old stuff laying around)
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Old Aug 22, 2010, 03:31 AM
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oh, you just add it in front of bearing, behind the collar. cool

ok got ya, will see if i have a thrust bearing out an old diff, for my small motor shaft.
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