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Old Jun 09, 2009, 11:31 AM
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jschneider's Avatar
SE Wisconsin
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Marx Chris Craft Constellation

Hello Folks,

I could use some adivce from the more experienced modelers. I have just finished installing new running gear, motors, and speed controls into my Marx Constellation. My first problem is the prop shafts vibrate like crazy. I've tried aligning the motors the best I could, but they still vibrate. I know its possible that they were bent, but is there anything else that could be causing this?

My power set up is this....(2) 540 motors from the Traxxas Villan with, I beleive, 2:1 gear reduction turning (2) 1 inch diameter four bladed brass props (counter rotating), two speed controls and two 7.2 volt batteries. I know it sits low in the water, but it hardley moves. With the same set up in the Villian it really moved along nicely. So, I am thinking that either the props are too small (but I really can't increase the size too much), the gear reduction should be removed (direct drive to turn the props faster), or eliminate (1) speed control and (1) battery to make it lighter? Any thoughts? Does anyone know of a speed control that uses one batter to two motors? I know its not a race boat, but it would be nice to have it move along at a scale speed and not sound like its gonna vibrate to peices at anytime.

I will try to attach a photo, its my first attachment so we'll see how it goes.

Thanks for the input.

Regards,

John
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Old Jun 09, 2009, 11:57 AM
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Madison, MS
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She's a nice looking boat, John.
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Old Jun 09, 2009, 12:00 PM
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Chula Vista, Ca.
Joined May 2006
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First thing you need to do is eliminate the vibration. Try running only one shaft at a time and see if you can determine which one is vibrating, then try running it without the prop to see if it goes away. It just a process of elimination. You may need to move some equipment around to get it to sit properly in the water. There is a sticky at the top of one of these forums about how to do your electronics, you can find the schematic for two motors and one speed control http://www.rcgroups.com/forums/showthread.php?t=783582 Here's the diagrams
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Old Jun 09, 2009, 12:35 PM
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Valencia, CA
Joined Oct 2002
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It is basically the same kit as the Lindbergh Constellation, so maybe you can search this forum to see what other builders are using. Since you are size limited on the props, you probably don't need the reduction. You may also be able to find some similar sized props but with more pitch.

As for vibration, are you using universal joints to the shafts? Are you using the stock cast kit props or did you buy new ones? You might need to balance the kit props if you used those. Suspend the shaft on a couple of box cutter blades taped to a piece of wood a couple of inches apart and see if the same blade always ends up on the bottom. If so, file off a little material until it balances.

Pete G.
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Old Jun 09, 2009, 12:42 PM
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Umi_Ryuzuki's Avatar
PDX, OR
Joined Dec 2002
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U-joints, If the u-joints have a larger diameter hole than the shaft size, they will
tighten down excentrically and cause vibration.

Propeller out of balance see previous post.

Shafts may be too long, and could gyrating inside the stuffing tubes.
If you have a picture of the set up, we might be able to notice other possible causes.
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Old Jun 09, 2009, 01:12 PM
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SE Wisconsin
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Thanks for the info I should be able to get a picture of the set up possibly tomorrow.

The original cast running gear was junk so I purchased new shafts, stuffing tubes, and props. If you turn the shaft over by hand you can see that it moves back and forth up by the U-joints, both shafts do the same thing. I am thinking that the U-joints are possibly bad...even though they are also new. The fit of the shafts into the u-joints is very snug so I don't think the set screw would throw it off balance. Just when you think you have it ready to go, relaibly, something else pops up. She was almost lost on the madien voyage due to a broken rudder tube. Got that fixed and the motors came loose, the u-joints let go and it wouldn't move. If the wind wasn't blowing the right direction it would have made for a very refreshing swim this time of year.

Anyway, thanks again I will investigate some more.

John
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Old Jun 09, 2009, 01:14 PM
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Swieqi Malta
Joined Nov 2005
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If I were you, I would remove the gear boxes and use 35mm two bladed props. These props will allow your motors to develop their full revolutions

Check if you have an unbalanced prop, it could be the culprit producing the vibration

Nice boat thanks for sharing

Stephen
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Old Jun 09, 2009, 01:15 PM
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SE Wisconsin
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Jeepers, thanks! I can't take credit for building it, but she does show well. The original builder must have used some really cheap super glue because just looking at it will cause parts to break off. I've gotten almost everything refastened with plastic glue now. It is a work in progress.
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Old Jun 09, 2009, 02:13 PM
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Valencia, CA
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Quote:
Originally Posted by jschneider
If you turn the shaft over by hand you can see that it moves back and forth up by the U-joints, both shafts do the same thing.
John
If the shafts appear to move 'back and forth' up by the u-joints, you may not have a very good fit at the upper end of the stuffing box. The bearing may be much too loose. Otherwise, if they fit right at the end of the stuffing boxes, they may be bent to give the appearance of moving "back and forth" at the u-joints. Is there a bearing at both ends of the stuffing box? How loose is the fit on the motor end?

To check to see if the shafts are bent, roll them on a piece of glass.

Pete G.
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Old Jun 09, 2009, 03:23 PM
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SE Wisconsin
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Pete,

Yes, I do have bearings on both ends of the stuffing box and they appear to fit very tightly. The u-joint fits tightly on both the shaft ends and the motor ends. This is why I am lead to beleive either the shaft is bent or the u-joints are bad. If the shafts are bent, they would have been bent at the vendor.

I have seen some photos of people bracing the stuffing box to the hull. The only place on my boat where the stuffing box is attached to the hull is where it goes through the hull. Should I brace it to the hull where it attaches to the u-joint as well? To provide additional support?

Thanks,
John
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Old Jun 09, 2009, 04:41 PM
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Monterey Bay California
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Quote:
Originally Posted by jschneider
Should I brace it to the hull where it attaches to the u-joint as well? To provide additional support?
Yes, I think that is a very good idea- that should help solve the problem-

Nice boat by the way!
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Old Jun 09, 2009, 05:00 PM
Old wreck in Milwaukee
Prins Willem's Avatar
United States, WI, West Allis
Joined May 2007
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Very nice looking model. We have had several Lindberg Connies in our club. The prevalent drive was 540 or 550 can motors running direct drive. You got all the best advice on troubleshooting your vibration already so I don't have anything to add there. My one observation is in the side shot of your model it seems to be running out about the way a full sized CC would. These boats did not plane. I had a friend who restored a old CC cabin cruiser (can't remember if it was 32' or 34') with twin 230 Chevy's. he said she would knock down an honest 25mph if the wind was from behind.
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Old Jun 09, 2009, 06:47 PM
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United States, CA, Santa Clarita
Joined Dec 2005
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Your friends boat needed bigger engines. The boat will plane if he had gotten one with a bigger engine package. Boats like cars are not only made with one power package it can be what the customer wants for the most part and within reason. Let time pass and newer engines from other manufactures will be fitted also.

Steve
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Old Jun 09, 2009, 10:34 PM
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The next issue (July-Aug)of SIS should have an article by me on how I did my Lindberg Connie. I used surplus Maxon Swiss motors direct driving two Brass 3-blade props. I built my own shafts & tubes. The shaft tubes run all the way out to the struts. No vibration problems, but the motors got hot, so I had to install water cooling for them. Ya can't win. However, she runs great.
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Old Jun 09, 2009, 11:14 PM
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Monterey Bay California
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Quote:
Originally Posted by John Fryant
The next issue (July-Aug)of SIS should have an article by me on how I did my Lindberg Connie.
Sounds like a good article- Any idea if Lindberg is ever going to re-issue the kit?

I have kind of written that possibility off-
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