New Hydro

[pda75]

Hi

I have started a new rigger : many picture are here.

http://www.offshore-rc.com/forum/index.php?showtopic=21130&view=getnewpost&hl=&fromsearch=1

It a 1,25 meter (~50 inch) long rigger about 16 lbz. It will be powered with a lehner 3060/8 with lipo 10S2P. ESC is an YGE200 Navy. EPR 5000 means in french "nuclear plant 5000" and in english "Electric Propulsion Rigger 5000 watt"

the boat is designed for oval racing with 90 nitro riggers

Feel free to help me as I have not found many similar projects

cheers

Pierre

 

[pda75]

Here is the engine : it can move forward and backward in order to avoid flex cable reduction

Here are the outside plugs. The small one is a molly connector for the PowerPanel of eagle tree.

Cheers

Pierre

 

[pda75]

For fun, the sponson compared to mono 2 (70 cm ~ 27 inch) electric boat

Pierre

 

[pda75]

Center of Gravity is a key issue. The implementation in the following:

2 lipos in front, the motor and 2 lipos in the back. The weight on the strut could be in a range of 700 gr to 1,2 kg (eg 0,9 lbz to 2,1 lbz).

My calculation based on rpm and propeller size (likely to be an octura X460) is that the right position of the CoG is obtained with a weight of 1,5 lbz on the strut.

The flex wire is about 60 cm long: Rember the the motor can move backward and forward in order to cope with flex wire length reduction. I hope that it will work well anf the flex will not blow up.

cheers

pierre

 

[TinoAlmanza]

Can't wait to see this one run!

 

[misshydro]

Center of Gravity is a key issue. The implementation in the following:

2 lipos in front, the motor and 2 lipos in the back. The weight on the strut could be in a range of 700 gr to 1,2 kg (eg 0,9 lbz to 2,1 lbz).

My calculation based on rpm and propeller size (likely to be an octura X460) is that the right position of the CoG is obtained with a weight of 1,5 lbz on the strut.

The flex wire is about 60 cm long: Rember the the motor can move backward and forward in order to cope with flex wire length reduction. I hope that it will work well anf the flex will not blow up.

cheers

pierre

man that a different rigger.. never seen one like that before..I just got one this christmas. a aeromarine .21/.45 stinger rigger.. can wait to see your run..

 

[R.J.West]

Center of Gravity is a key issue. The implementation in the following:

2 lipos in front, the motor and 2 lipos in the back. The weight on the strut could be in a range of 700 gr to 1,2 kg (eg 0,9 lbz to 2,1 lbz).

My calculation based on rpm and propeller size (likely to be an octura X460) is that the right position of the CoG is obtained with a weight of 1,5 lbz on the strut.

The flex wire is about 60 cm long: Rember the the motor can move backward and forward in order to cope with flex wire length reduction. I hope that it will work well anf the flex will not blow up.

cheers

pierre

My first thoughts were that you may have too much weight over the transom/strut area. Have you considered keeping all four lipos up front and moving the motor back to where the second set of lipos are at?

 

[pda75]

My first thoughts were that you may have too much weight over the transom/strut area. Have you considered keeping all four lipos up front and moving the motor back to where the second set of lipos are at?

Yes but the motor is heavier than two lipos.

the Lehner 3060motor is about 1,5 kg though the website says it's 1,2 kg.

Cheers

pierre

 

[R.J.West]

My first thoughts were that you may have too much weight over the transom/strut area. Have you considered keeping all four lipos up front and moving the motor back to where the second set of lipos are at?

Yes but the motor is heavier than two lipos.

the Lehner 3060motor is about 1,5 kg though the website says it's 1,2 kg.

Cheers

pierre

Ahh, thats what i thought, but wasnt sure. Well then, I guess all you have to do is run the boat and see if it works, and take it from there! have fun

 

[GiantScale13]

Wow.. sweet!

 

[pda75]

some more pictures

 

[Blackout]

some more pictures

Your boat looks great, looking forward to seeing a video of it running!

Do you have any idea on finished weight and how it compares to the nitro riggers of that size?

 

[pda75]

Expected weight will be 15 to 16 lbz, eg 2 to 3 lb more than nitro riggers of the same size.

However, the motor is probably 25% more powerfull. (4000 W vs. 5000 W).

In theory, 1 lbz additional weight requires additionnal 250 Watt at 130 km/h (80 mph). I don't whether this calculation is acurate but it gives hope !

A+

Pierre

 

[ww29]

nice boat.hope to see video soon.

 

[pda75]

Hi

There are still some vibrations in the transmission.

For all my boat, without propeller, when the motor rotates full speed, when I put a finger on the hull, I cannot feel any vibration. All of them are built with a flexcable transmission with teflon. The flex diameter below 3/16.

For the EPR, it's a 1/4 flex cable in a 5/16 brass tube. The strut is from rocketcity with a bushing. There is no teflon as the rotation speed is to high (32-33 000 rpm) and the teflon is likely to melt

The brass tube is filled with oil.

Without propeller, when the motor rotates up to 15 -20 000 rpm, it is very smooth without vibration. At full speed, there are vibrations. It is not that terrible but any small piece of wood or plastic vibrates or jig.

Is it normal with a1/4 flexcable ?

Any suggestion ? Grease instead of oil ?

Regards

Pierre

PS : the motor mount is fine and so is the bushing. Here are some pics

 

[BACKEMF]

Wire drive may get rid of that noise/vibration.

You have a long run of flex cable & very small bend, it must be slapping around inside.

 

[Jim Caldwell]

Put a very small S bend in the tube between the tub entry and the motor it doesn't take much 1mm on each side of the S is enough usally.

 

[pda75]

Thanks for the answer

you're right the flex is 25 " long inclunding the prop shaft. I should bend it

The good news is that it is possible to build a 1/4 flex transmission with no vibration at 32 000 rpm.

Regards

Pierre

PS some more pics

 

[AlanN]

I have had the same issues with some 1/4" cables on 3060 or large motor setups. Jim is right that an S bend can help. But there are other things to look at too. How much clearance is there between the cable the stuffing tube? I prefer to use tubing that the cable just fits in to and double walled brass...not teflon. If you go that route an S bend may make it worse. A constant radius on the stuffing tube has worked for me also...constantly putting force on the cable in the bend helps prevent cable whip. I have also seen an 1/8th scale with larger ID tubing than I use with an oiler setup that works well. Each cable acts differently so it may take a few pieces of tubing to figure out what will work best for you. Also, some cables are not balanced too well....that can be another issue!

 

[pda75]

thanks.

The brass tube inside diameter is 1/4 + 1/32 ". There is no smaller brass tube for such a flex. the radius of the brass tube is wery big 3,5 m eg 10 feet : the brass tube is almost straight.

First test : I will use another flex cable.

Regards

Pierre