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10-26-2006 11:13 PM  11 years agoPost 21
Paul99

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red_z06 I'm using the all plastic head that came with the CDE. The balls are older Aluminium ones.
Can you calculate approx. by how much the plastic links and aluminium balls shrink for each f?

Tintin - odd you felt nothing - I didn't feel it during flights but checking the head right after at home it got noticeably stiffer before loosening up again.

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10-26-2006 11:26 PM  11 years agoPost 22
Tonic

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Des Moines

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OK, this is all good info. I can deal with the batteries no problem. The only crash I've had was when a belt snaped so that's why I thought that cold weather would compound any belt isures.

Tonic

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10-26-2006 11:34 PM  11 years agoPost 23
OICU812

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Edson, Alberta, Canada

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Just keep them warm in your pocket or vehicle till you fly. I have flown up to -10 deg C and no worries, but I would not fly colder than that for certain. But I fly my packs, then leave and nothing is sitting for a big amount of time. The only concern or thing that was a difference for me was the belt loosening from the boom shrinking up from cold.

...Once upon a time there were Nitros, flybars and frequency pins...

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10-26-2006 11:45 PM  11 years agoPost 24
red_z06

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Dumont, NJ

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Plastic vary in CTE as much as 3-4 times from the lowest to highest. If nylon links are used over aluminum balls, gap will increase at a rate of 3.2x10-5 in/in/deg f. That means 0.000032inch per inch per deg f. if they were both 1inch at 0def f, then at 100deg f, plastic will be taller by 0.0032 or slightly tall than by human hairs thickness. But, since the balls are about (guessing) 0.15inch dia., the gap will increase by 0.0005inch or so.

www.JustinJee.com

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10-27-2006 12:34 PM  11 years agoPost 25
Tonic

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Des Moines

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Red,

Wow, how do you konw that stuff?

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10-27-2006 12:44 PM  11 years agoPost 26
red_z06

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Dumont, NJ

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I'm a mechanical design engineer.

www.JustinJee.com

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10-27-2006 01:06 PM  11 years agoPost 27
Tonic

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Des Moines

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Red,

OK, I am going to do some measurement then. Now … can I use you figures or are they just estimates?

Just kidding! I had to show your reply to my wife. Just kind of take me back a little how much knowledge people have on this form. Love it!

Tonic

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10-27-2006 01:30 PM  11 years agoPost 28
Tintin

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Akershus, Norway

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Red, how bout calculating abt how much the boom will shrink in cold. I have a hard time believing it's noticeable on belt tension, even on the 600.
I calculated it once and as far as I remember it was less than 1 mm...give it a go
If I do an estimate based on your estimate from the links I should get 1,2 mm I think.

“Getting an inch of snow is like winning 10 cents in the lottery.”

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10-27-2006 01:31 PM  11 years agoPost 29
red_z06

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Dumont, NJ

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Tonic:

In most cases, rule of thumb is CTE range is steel<aluminum<plastic in that order. Actually there is one factor that is more significant than CTE that may have caused tightening. It is due to hygroscopic (moisture swelling) nature of most plastic. That means parts get bigger (as much as 0.1% or 0.001 per inch) as it absorbs moisture from air during hot humid summer months and shrink during dry months on top of thermal expansion. Nylon is one of the worst in terms of moisture retention.

www.JustinJee.com

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10-27-2006 01:45 PM  11 years agoPost 30
red_z06

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Dumont, NJ

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Tintin:

Timing belt is somewhat more complex as the material is a composite of rubber and fiber core. If it were straight rubber on aluminum boom, I would say belt tighten in colder and dry winter weather. However, depending on the fiber (do not know what they use) used, it can prevent the belt rubber from expanding and prevent rubber from shrinking during cold weather.

I can calculate it for specific timing belt brand provided the mechanical data can be obtained.

This is why a belt tensioner is always used in automobiles.

www.JustinJee.com

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10-27-2006 03:20 PM  11 years agoPost 31
Tintin

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Akershus, Norway

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I was thinking more of how much the boom would shrink as this is supposedly a problem.

I always thought the belt tensioner was there to take up slack as the belt wears/stretches.

“Getting an inch of snow is like winning 10 cents in the lottery.”

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10-27-2006 03:35 PM  11 years agoPost 32
red_z06

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Dumont, NJ

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Tintin:

Aluminum CTE is 0.000013 inch/inch/def F
That means for every inch of boom length it will change by 0.000013inch per degree(f) of temp change.

For example, 20inch tail boom which is normally flown at 100def f, when subjected to 30def f temperature will shrink to;

0.000013in/in/deg(f) x 20inch x (-70deg(f)) = -0.018inch

Minus denotes shrinkage. You can plug in different length and temp change for your needs.

www.JustinJee.com

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10-27-2006 05:58 PM  11 years agoPost 33
Paul99

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Thanks Red for helping in.
the gap will increase by 0.0005inch or so.
Such a gap increase or decrease will not affect the linkage stiffness will it?.

What gap change will affect stiffness noticeably? 0.005Inch?

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10-28-2006 09:36 AM  11 years agoPost 34
OICU812

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Edson, Alberta, Canada

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That was alot of technical jargon just there, lol.

...Once upon a time there were Nitros, flybars and frequency pins...

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10-28-2006 10:25 AM  11 years agoPost 35
Tintin

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Akershus, Norway

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Thanks for confirming, 0.3 mm shrinkage on a TRex then, I don't think I'll bother adjusting this winter either.

“Getting an inch of snow is like winning 10 cents in the lottery.”

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10-28-2006 12:55 PM  11 years agoPost 36
red_z06

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Dumont, NJ

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Tintin:

The ball link calculation was a relative change ( link - ball ) so it shows increasing/decreasing gap.

However, on the tail boom, it was the actual change of the boom itself with temperature. I do not have the data for the tail drive belt. BTW, most of these data are emperical meaning obtained from a lab environment.

I would suggest you set the heli in the temp you will be flying and adjust it there and don't worry about it getting tight or lose indoors.

www.JustinJee.com

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10-28-2006 01:04 PM  11 years agoPost 37
Tonic

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Des Moines

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I did notice that the belt was loose after flying outdoors and then returneded to normal tention after it wormed up inside. I think I'll ajust the belt to 50 degrees, then I hope it should be good on 45-55 degrees days.

I charge my batteries out in the garage that I heat to 55 degrees. Is there any lipo charging considerations at this tempeture?

Tonic

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10-28-2006 01:11 PM  11 years agoPost 38
red_z06

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Dumont, NJ

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Tonic:

I have not experienced any degradation in performane ( discharging ). For charging, I would not worry about it much unless you are chaging in sub zero temps. If you are concerned about it, is it always a good idea to reduce charging rate to 1/2c or so. I have not persornally experienced any issues even during pre-balancer port days.

www.JustinJee.com

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10-28-2006 01:17 PM  11 years agoPost 39
Tonic

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Des Moines

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Red,

Thanks for you help, I happy to find that winter flying is OK on batteries and machine. Winter is very bitter and cold in Iowa but we do get spells where it will worm up into the 40's and 50's ...so hope to get some flying in when the weather permits.

Tonic

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10-28-2006 01:43 PM  11 years agoPost 40
Nasscar][

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Delaware

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would one of those portable battery blankets do the job at keeping the lipos warm?

In previous post I had staded that I noticed a change in the power during cooler weather.

I'm thinking about going down to Walmart and looking for either a electric blanket or one of those electric cold / warmer coolers.

Nas,

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