High RPM driveline setup

[nate]

I have looked and can't seem to find any good threads on tips and tricks to setting up a good driveline to support over 40k rpms. Can a few members chime in on better ways to setup the stuffing tubes, different bends, mounting, sizing up drive lines for different setups ect.

Im looking to see what is better, between .130 - .250 size drive shafts. Does more aggressive bends in the drive line affect vibration levels?

[olwarbirds]

Im interested in this too.....

[iridebikes247]

Which boat? That will help a lot.

[olwarbirds]

Daytona/Genesis NEU 1521 1Y (1600kv) Castle 240 8S ...so I am going to be close to that 50,000 rpm....

[Jeff Wohlt]

Wire...done right..... saw record of 140 mph and 50,000 rpm.

[nate]

See that what Im talking about ^ that didnt really help much, explain done right, the tricks? Im assuming that the shorter the drive length, the better, why is wire better? I want to know all of how to...

[nate]

Particularly Genesis/daytona right now.

[iridebikes247]

I have no experience with a wire drive. Here are a few pointers

1. Make sure your prop is perfectly balanced, absolutely perfect. Contact dasboata or andy brown if you doubt your tuning.

2. Make sure your motor bearings are in good shape, and run an mbp modelbaupirate collet. The difference is quite noticeable over an octura collet.
dri
3. Strut, well that depends. You can run something from the site and just install lead teflon bushings, also available here on OSE.

--This will help you a lot with getting a nice setup that runs smoothly. Also, do yourself a favor and run a teflon liner. I give the outside a light scuff with 80 grit sandpaper and then CA glue the liner in place, I have never had one spin. Stay away from more than one bend, if you take your time lining everything up you will only need one bend. Some drive lines sound horrible out of the water but run fine under load, I think with the advice given you'll be happy with how smooth it is. Also when you set the collet distance from stuffing tube make SURE for to keep the gap small so that like 5mm of flex shaft is exposed, no reason for more

[martin]

Just my personal experience with wire drives that I make, longer is better as you get a shallower curve in the stuffing tube, wire gives less friction + less rotational weight over flexes. I like both wire & flex depending on application its in.

[olwarbirds]

Motor has 8mm shaft Im using the MBP collet....for the setups Nate and I are running is .187 the flex to be using ? Not to start a debate, I was understanding that for a high rpm SAW setup a S bend stuffing tube was the way to go, but what iridebikes said makes total sense to me also....

I have never used a wire drive so Im lost on how to do them.....

[iridebikes247]

Keep the bend simple, 1 is best. Use teflon. Also use .187, so its an 8mm shaft what kinda motor is going in this genesis project, sounds big. You don't need a wire drive and you're not going 140 mph so just use a flex.

[martin]

Some cats are not the best thing to use wire drive in due to the height of the motor sat up on the tunnel down to the depth of the strut. You end up with to much curve in the tube for wire, as said just go with flex as the tend to be more reliable than wire in my experience for every day running. I believe a number of SAW records have also been set with flexes.

[olwarbirds]

My Genesis/Daytona ....Neu 1521 1600kv 8S castle 240A with capbank !! going to test run using 6S...Mod (Nate) if I remember correctly is building a twin using Leo 4082 2200kv.....so 2 very different setups, but using flex or wire and stuffing tube options still apply....Tks for responses guys....Im going flex, just because I'm more familiar with it and Id like to break 100mph but im not looking to set new speed records so yeah 140mph is a goal im not ready to attempt ...YET..... DJ

PS; I would like to learn how to setup wire drives though, for future hotter setups......

[NativePaul]

I'm sure you know that is a lot of RPM and very small changes in prop can cause very big changes in amp draw at those speeds, be very careful when propping up (sorry, I'm sure you have heard that already from different people but it had to be said).

Wires and flexes are quite different, because you dont need a full length stuffing tube around a wire it doesn't really matter how long it is the bigger the radius of the bend the better so a longer driveline is optimal, with flexshafts a bigger radius of bend is still better , but it will tie itself into knots if it is unsupported so you need a full length stuffing tube and the shorter the stuffing tube is the lower the drag, so it is a compromise between length and radius.
For an example a JAE.21 has around 10" of flex, I changed mine to wire and to get a reasonable bend I now have 20" of wire, I prefer it now, but that has more to do with where the motor and battery are, than what the shaft is made of. My 36"ish Sprintcat has 19" of wire for a decent curve, a Genisis has a lower tunnel so could use a little less, but I believe the canopy starts a fair bit further back so a single motor placed under there would have to have more bend than I would like for a flex.

Whatever drive you go for the bigger it is the more robust it is and the smaller it is the less drag it will have, both in terms of cutting through the water (not something you have to worry about as you won't be doing 100mph when there is a ripple on the water, never mind enough chop to reach the stuffing tube on a narrow cat), and rotational drag, as the bigger the diameter is the faster the surface is moving for a given RPM, and more energy it takes to bend the wire/flex through 360 degrees which is not inconsiderable as it happens 50,000 times a minute. I have no idea how much power it takes to make a Genesis do 100 as I have never done it, but I can say that a flex or wire that is just strong enough will have less drag than one that is twice as strong as it needs to be, on the other hand one that is not quite big enough may whip around inside your boat when it breaks and ruin the hull and gear, Every decision when designing, building, or fitting out a boat is full of compromises.

Because you are using high RPMs to make your power your drive will have more drag, but you will be using a smaller prop torque so your drive can be thinner which reduces the drag, another compromise, there may be an ideal for your use of your boat with your setup and your gear, but there is no perfect and certainly no perfect for everybody.

[olwarbirds]

Paul, I have no problem at all being told or reminded to be careful. I am concerned about the amount of RPM im going to be turning eventually here. I been doing High Speed electric planes, Pylon racers and EDF (electric ducted fan) jets for alot of years now and understand amp draw etc...magic smoked more jets than Id like to admit, but FE boats even though I been doing them a few years now, I still feel im in a big learning curve here. I do read and pay attention to all advice, so please advise on...tks .... DJ