I didn't made a video but can explain you how I build a straight shaft years ago with an alternative cam lock system to secure the lower part of the shaft, it was so easy to make, you just need to find the right accessories.
1- The hardest part was to find a shaft to fit on the fiber rod of your detector, I was lucky to find Worth garden tools. they have a this tool name "long reach pruner", it's internal diameter fitted exactly to my Beach hunter lower fiber rod (another interesting point is that its anodize aluminum).
http://www.landscapersstore.com/worth-long-reach-pruner-w1034.html
2- You will also need a bicycle bar end (there are lots of cheaper model to customize your shaft)
http://www.utahmountainbiking.com/fix/bar-end.htm
http://www.amazon.com/Profile-Design-Brief-Mountain-Bike/dp/B0035X42YO/ref=pd_sbs_sg_12
3- For the twist or cam lock I had to buy a, what some plumbers call, quick repair coupler system, its an adapter that connects two ends of a pipe together, for my project I used
3/4" coupler. Normally this coupler can help to prevent the fiber rod to twist, but as some manufacturers have different internal diameter specifications, it will be difficult to find the right fit. Some duct tape can be used on the fiber rod to add more thickness and secure it in place inside the coupler (You will also need to drill some parallel holes on the shaft for fiber rod compression pin).
http://www.plumbingsupply.com/quick-repair-fittings.html
Tools
You will need a drilling machine, drill bits, duct tape and J.B Weld
How to proceed
- Dismantle the Worth long range pruner and the arm rest of your detector. Place it on the Worth shaft and mark the holes for the bolts and nuts.
- Drill the holes with appropriate drill bits and assemble the arm rest to the shaft.
- Adjust one the bicycle end bar on the shaft according to your arm length and grip, tighten the integrated nut and bolt of the end bar (note: you can use some J.b weld or duct tape on the rod to secure in place the end bar before tightening the bolt).
- Place the coupler on the end of the shaft
- Slide the fiber rod inside the other end of the coupler, finger tighten the coupler and gently twist the fiber rod to check if it fits inside the coupler.
- Remove the coupler and drill parallel holes on the shaft for the compression pin of the fiber rod.
- Add some J.B Weld to the end shaft and hold the coupler in place.
- Et voila! you get yourself a straight shaft.
As a result, here a picture (with a flashlight adapter) I've taken two years ago. Once I get back my camera I'll take some more detail pictures of this straight shaft