Gluing a flex cable to prop shaft

Assembling your own flex cable and prop shaft is a great way to save some money. There are a couple of methods used to attach the prop shaft to the flex cable. The soldering method that Octura recommends is outlined in the directions that come with Octura parts. However, I feel the soldering method is harder and more prone to error than the way I'm going to outline in this article. We use the glue method. 

Here are the items you will need.

Flex cable and prop shaft. Most Fast Electrics use left-lay flex cable. See our flex cable article for cable size guidelines.
                                   
A sleeve retainer-type glue. We use and sell  Loctite 638 but some people suggest Permatex High Strength Sleeve Retainer. The Permatex is a bit easier to buy at your local auto parts stores. We've never tried the Permatex. So I can't comment on its strength.

1 Piece of medium sandpaper
1 Dremel tool or drill
1 Sharp 1/16" or similar drill bit.
Rubbing Alcohol and a rag.

First take a look at the end of the prop shaft and remove any loose filings left behind when it was drilled by the manufacturer. Just tap it on your bench upside down a few times.

 

Next, we are going to measure how much of the flex cable fits into the prop shaft hole. We are going to lightly sand that part of the flex cable. This will help give the glue a better bite on the flex cable and remove the plating, like in the below picture. After this is done take your rag with alcohol on it and wipe down the end of the sanded flex shaft. This will help remove the oils and fillings. Set the flex aside to dry off completely.

                                                   

Next to help the glue bite to the inside walls of the prop shaft hole we are going to "nick" the inside walls of the hole. This is done easily with the drill bit by sliding up and down at an angle at a slow to medium speed on your Dremel tool. Try to nick up most of the area inside the hole. Take care to not drill to much. It should take no longer than 30 seconds to do this. Then tap it on your bench again to remove the fillings inside. If you don't have any fillings come out, there can be a few reasons. You didn't have a sharp enough drill bit and the process needs to be done again. Or it could be that when the original prop shaft hole was drilled the manufacturer could have left behind some cutting oil to which the fillings are binding to.

                        

 
                           

Now we have to thoroughly clean the inside of the prop shaft. We first need to tightly twist/wrap a piece of paper to a size that's a bit larger than the prop shaft hole. We use the scrap octura packing that comes with the flex cable for this. Then dunk the paper into rubbing alcohol.
                           

 

Now twist the paper inside the hole. Keep twisting a few times than remove the paper. You should seen some of the filings and cutting oils. Repeat with a new piece until when you remove it, the paper is nice and clean. Once clean insert a dry piece and twist. Once its removed in should come out as clean as it went in.

After the first pass you can see the tip is brown from the cutting oils.
                            

Now that we're done prepping the parts its time to start gluing it all together. We are now going to coat the inside of the prop shaft hole first. The Loctite 603 is so thick that it won't flow inside the hole on its own. I use scrap ends of plastic tie wraps to push the glue inside the hole and rub it on the inside walls making sure to cover all the entire area.

 
                                 

Next, make sure the flex is dry by wiping it with a clean rag. No grease should be on the rag. If there is grease showing on the rag clean the shaft again with alcohol. Than use the glue to cover the part of the flex shaft that will be in the prop shaft.
                           

 

                         

Next, we are going to assemble the two pieces. This is the easy part. Just slowly push the flex into the hole and twist it a bit. Some glue will come out. Just wipe it with a clean rag.
                           

 
                           

Allow it to dry a day or so before use.
                           

     
Shaft and Cable Glued and Ready for adjustment.

Final adjustments to the Flex Assembly.
First, install the drive dog where you want it on the shaft. To find this area select the largest prop you will use on the shaft. Try it on the shaft with the prop nut or bullet nut. Once you know where you want the drive dog to go, mark the area by tightening the grub screw a bit. Then loosen the grub screw and remove the drive dog. There should be a small nick/mark on the prop shaft where the grub screw was tightened onto the shaft. At this location on the prop shaft make a small flat spot with a file or dremel tool with a sanding disk. Now put the drive dog back on and tighten the grub screw, making sure the screw is tightening on the flat spot. If you want a more permanent drive dog you can use the retaining glue to help secure the dog to this area. Just apply the glue on the shaft and slide the drive dog on. Then tighten the grub screw. This will help ensure the drive dog doesn't slip under the heavy prop loads.

Next, its time to make the final cut to the cable.
Measure the total length needed and add 3mm for the space needed between the drive dog and the end of your strut.
Remember the cable can be shortened, but not lengthened. So cut the cable a bit longer than you may need and shorten it to adjust. Once you have made the final cut, roughly sand the last 1" of the cable end. Then use a soldering iron to solder the last 1/2" of cable solid. This will help stop the cable from unraveling under heavy loads.