Propshaft to flex shaft / MHZ drive

[uncledirty]

A lot to be done before maiden voyage due (hopefully) on 2010 summer. Lakes are on ice the next 6 months... So I ll be bothering you during the whole winter.

I got the mhz drives for mystic and now I am wondering how to attach flexshaft to prop shaft. It says on the MHZ site that this drive has "universal 2mm bore". So the hole in the end of propshaft is 2mm. There is no way it could be largened to 4,7mm which was the mhz suggestion for flexshaft. There is just not enough material... for example the propshaft it self is that 4,75mm... The drives themselfs are from mhz catalogue and sized "for 44,8" hull"

"This drive has a propshaft (shaft for props) of 3/16`` (4,75mm)
The milling for the propshaft (flex or steal) is universal 2mm and able to get enlarged up to 3,2 mm or 4,7mm " //mhz-powerboats.com

I will ask MHZ, but before some questions to be able to ask right questions:
- could this be done with coupler from 2mm hole to 4,7 to attach to flex shaft? (couldnt find any suitable)
- have somebody experience with mhz drives and similar situation?
- drilling 2mm to 4,7mm with these tolerances is diffucult job for professional and for me beeing incompetent in all walks of life - impossible

[Jeff Wohlt]

A bit confusing but If you need something lathed and fitted let me know. THta would be very thin walled on the stub but could work. They may be reducing the size of the cable in the stub which is easy to do.

I fit 3/16" cable in 3/16" stubs. But you have to take a layer off the cable.

[uncledirty]

Probably I could drill it to 3,5 and leave enough material. If one can peal of the layer from the cable and still get to last enough, then no problem.

How about glueing a coupler to that 2mm hole on prop shaft and coupler should have 4,7 in the other end for flex shaft?

[Gerwin Brommer]

Which motors are you gonna use ?
Why not just using 2mm pianowire ?

[uncledirty]

I am choosing between Lehner 1950 or 1940. Probably I ll end up buying 1950/7-8.
Is 2mm enough for those motors? I was planning to run those with 5s or probably 6s lipos.



I have some problems also with another of the drives (another wont rotate at all even by hand) and MHZ promised to come back to that problem. I could ask what MHZ recommends.

[Anbjorn]

Hi,
Seem to me that we are going to build almost identical boats.
Here is what I am planning to do:
http://forums.offshoreelectrics.com/...ad.php?t=11400
Anbjørn

[uncledirty]

good luck on your building! Hopefully you get the boat on the water before me, cuz I think mine will take time. :) Atleast the sea will be off ice there?

On c5000 hull and mhzdrives I think there is a possibility to install engine and drives so that whole powerline is straight. At least with lehner 1940 being so narrow motor. Have to think using wire. Would solve my problems...

so 2mm wire, grease, teflon liner and aluminum tubing.

Does 2mm pianowire shrink when stressed. Do I need a gap between strut and drivedog? Wires would be only max 15cm long because I will put motors to way back of the boat.

[Gerwin Brommer]

A straight pianowire isn't the best option. Unless you
have a teflon tube and outer tubing around it.
If you wanna use "bare wire" you have to have a slight curve in the wire, to avoid
swinging of the wire. A gap between DD and drive : only a minor gap.
Check if the motor has no play in the axle ( axle can move forward and backward ) .
If the motor has play, the gap between DD and drive has to be bigger than the play in the motor.

[Anbjorn]

Good luck to you and your building too.
We have mostly ice free lakes during winter. On the west coats here it hardly ever drops below freezing point.
I ordered it the other day so I have not received it yet.
Yes the Lehner 19 series motors are quite slim.
I will mount them as far back as possible too, but the angle of the wire must decide the actual distance. I will aim for a slight bend in the wire.
I have decided to use 2mm piano wire and instead of teflon liner use a thin carbon fibre tube inside a brass tube. If the carbon does not work I can just pull it out and use a smaller brass tube inside the outer brass tube.
I realy don't like the thought of the teflon on these rpm's. Nor do I like aluminium tubing eighter.
I don't think the wire will shrink, atleast not much. Would say that if there is alot of clearence in the stuffing tube there could some shrinkage.
A mm or two of clerance between the strut and drive dog will should allways be present anyway.
Anbjørn

[Gerwin Brommer]

Anbjorn :
Please do NOT use a carbon tube as a liner for the pianowire !!!!!!!!!!!!!!!!!!!!!!

It will be eaten away within minutes. And more important :
Metal prop prop, metal wire, carbon : asking for glitches !!!!!!!!!!!!!!!!!

[Anbjorn]

Anbjorn :
Please do NOT use a carbon tube as a liner for the pianowire !!!!!!!!!!!!!!!!!!!!!!

It will be eaten away within minutes. And more important :
Metal prop prop, metal wire, carbon : asking for glitches !!!!!!!!!!!!!!!!!

Hm. Realy? I would have thought the carbon was more durable than the teflon liner.
Regarding glitches, alot of people are running piano wires and flex shafts in bare brass tubes both in gas boats and FE.

[Gerwin Brommer]

Maybe I was overreacting on the carbon, regarding glitches.
Unless your hull is carbon aswell !!!
Better to run a bare wire, with a small piece of brass tube as a "guide" , or use a
ballbearing to support the wire.

[Anbjorn]

It is allways best to look for what can go wrong when it comes to this hobby
The hull is carbon and then some.....

I have the ball bearings on my Sniper with 5mm wire drive. However not run yet. I Only tested the drive line with a Dremel at 33000 rpm for some minutes.

Where would i find bearings with ID of 2mm that can handle 60000rpm? Edit: Hm, I think I might found some at Boca Bearings.

Thank you for your advice. It is much appreciated.

[Anbjorn]

Gerwin,
I just ordered some of these bearings:

http://www.bocabearings.com/main1.aspx?p=product&id=7871&n=SMR692C-YUU_NB2

Then I have the option of going open wire with a couple of bearings supporting it.
Anbjørn

[Gerwin Brommer]

Use a larger dia ballbearing and make inner dia smaller with fillets.
But a simple piece of brass tube as a liner will work fine too !