RE: zoom 400 tail gear problem  
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All Forums >> RC Helicopters >> Electric RC Helis >> RE: zoom 400 tail gear problem
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RE: zoom 400 tail gear problem - 6/8/2004 7:46:41 PM   
Mr Hover


 

Posts: 53
Joined: 6/3/2004
From: Herts, UNITED KINGDOM
Status: offline 		I MAY have a solution.

I'm getting some sets of carbon 3D fins made - with a longer tail; this should stop the blades getting as close to the green stuff. I'll have some spares sets (minimum order qty and all that) if anyone wants them.(£8:50 ish)

I plan on making a brass / acetal gear at the weekend. Turning the profile is easy, broaching the tooth form will be a little trickier - but should be worth it.

I'll let you know how I get on.........

(in reply to jbalat)
       Post #: 26

RE: zoom 400 tail gear problem - 6/8/2004 9:39:31 PM   
Mr Hover


 

Posts: 53
Joined: 6/3/2004
From: Herts, UNITED KINGDOM
Status: offline 		Well here it is hot off the lathe.........

I'll fit it later and give it a spin. I think I may well find I've just transfered the problem to the crown gear at the motor; but if you don't try....

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(in reply to Mr Hover)
       Post #: 27

RE: zoom 400 tail gear problem (pictures corrected) - 6/9/2004 8:04:55 PM   
tedani


 

Posts: 13
Joined: 6/4/2004
From: KowloonKLN, HONG KONG
Status: offline 		Hi, I have sourced a large quantity of crown gears and metal shafts for slot car.

I must remind you that the crown gear for slot car is NOT direct replacement of the crown gear for your heli (See attached pictures. The crown gear in pink is the one for slot car and white one is the genuine tail gear). You need to do some minor work before using it on your heli.

About the hexagonal shaft, length of the one for slot car is 6.5cm while the genuine tail shaft is 4.2cm long.

I will not accept ANY responsibilities for using (or trying to use) these incompatible parts. Use it at your own risk.

If you are interested, please send me an email.

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< Message edited by tedani -- 6/10/2004 2:37:44 AM >

(in reply to jbalat)
       Post #: 28

RE: zoom 400 tail gear problem - 6/10/2004 2:00:18 AM   
meb48


 

Posts: 33
Joined: 4/1/2004
From: Alamo, CA, USA
Status: offline 		I may have been misunderstanding about which gear is the problem; the heli gear here looks like the #165188 tail input gear, that connects to one side of the motor spur; whereas the gear I understood to be the problem gear is the gear at the tail rotor assembly, i.e., the gear in the #165190 tail output shaft set, which is a shaft/gear combo (I just use the gear & stick the shaft in a drawer for who knows when.) The gear you show here looks very similar to the 165190, though with a shorter barrel; that shouldn't be a problem, as it can be shimmed. I see it is a 20 tooth; is the gear wheel approx 11 mm in diameter? If so, it would be worth looking at.

(in reply to tedani)
       Post #: 29

RE: zoom 400 tail gear problem - 6/10/2004 2:24:29 AM   
tedani


 

Posts: 13
Joined: 6/4/2004
From: KowloonKLN, HONG KONG
Status: offline 		Oh, sorry. I took a wrong part.

It should be the tail gear (see the picture below)

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(in reply to meb48)
       Post #: 30

RE: zoom 400 tail gear problem - 6/10/2004 2:42:49 AM   
tedani


 

Posts: 13
Joined: 6/4/2004
From: KowloonKLN, HONG KONG
Status: offline 		I have corrected the pictures in my previous post.

Sorry mate.

(in reply to tedani)
       Post #: 31

RE: zoom 400 tail gear problem - 6/10/2004 3:32:48 AM   
jbalat



Posts: 269
Joined: 3/3/2004
From: MelbourneVictoria, AUSTRALIA
Status: offline 		The latest pic looks good. Is it an exact copy and if so can we get some ?

(in reply to tedani)
       Post #: 32

RE: zoom 400 tail gear problem - 6/10/2004 6:14:44 PM   
Mr Hover


 

Posts: 53
Joined: 6/3/2004
From: Herts, UNITED KINGDOM
Status: offline 		Here's one I made earlier.........

The marks on the drive gear were made previously by the plastic gear. I've had a couple of flights and all seems ok.

I did notice while making the gear that the original plastic gear is not an overly good mesh. The gears only mesh / drive on the last 2/3 of the gear. A thin nylon washer in between the housing and the gear at the blade end would give a better mesh and longer life - in my opinion.

(I know the drive gear is a little too close to shoulder of the crown gear; hense the polished part, but I want to use a different part of the drive gear to monitor any wear)

Onwards and upwards.....

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(in reply to jbalat)
       Post #: 33

RE: zoom 400 tail gear problem - 6/11/2004 4:10:00 AM   
meb48


 

Posts: 33
Joined: 4/1/2004
From: Alamo, CA, USA
Status: offline 		What a beautiful job. You made on a lathe, I assume?

(in reply to Mr Hover)
       Post #: 34

RE: zoom 400 tail gear problem - 6/12/2004 6:27:51 AM   
jinsincity


 

Posts: 2
Joined: 6/12/2004
From: , NV, USA
Status: offline 		i recently purchased a shogun and in three weeks of just getting it dialed in to hover I have gone through about 5 of them so I have started to make my own from the tail input gear ans the stem from the old gears, lined them up shaved them down and glued them... seems to work so far . but once that rear brass pinion gear grooves from the wear of the stock output gear it seems that all you will do is to continue to chew gears.
they should have used a light weight transfer case with 45 degree gears. i mean if your flying and it strips out your done anyhow

(in reply to tedani)
       Post #: 35

RE: zoom 400 tail gear problem - 6/12/2004 4:39:07 PM   
Mr Hover


 

Posts: 53
Joined: 6/3/2004
From: Herts, UNITED KINGDOM
Status: offline 		Meb48 - Your correct. Turn the blank on the lathe, then put a 60degree tool in the tool post and broach the gear. I used a Myford Super 7 which has 60 teeth on the drive gear, the Crown gear has 20 teeth so the indexing is easy.

I have spent some hours looking for Mitre or Bevel gears. Closest I got was the following.

https://sdp-si.com/eStore/Direct.asp?Exp1=44&CP=Gears.htm

I think you need a 2:1 ratio, 20:10 teeth M0.25 which should make the big gear about 11mm OD. This is however half the size of anything I have found.

I have looked at making gears of that size out of some more suitable plastic than currenty used by Protech. Tooling is about £500 per gear. Then you can make them for pennies!! Anyone want to invest that sort of money???????

(in reply to meb48)
       Post #: 36

RE: zoom 400 tail gear problem - 6/15/2004 5:20:59 AM   
jinsincity


 

Posts: 2
Joined: 6/12/2004
From: , NV, USA
Status: offline 		I am now trying something. i think it is not really the brass on plastic situation. It is the size and pitch of the brass pinion gear on the back of the tail rotor drive shaft.
I think the diameter is too small and the stock gear is 11 teeth i think ans i am trying a 10 tooth gear, but with the increased diameter which creates increased tooth pitch is seems to be meshing big time, almost too tight but you can even hear the better bite and it is quieter. if it works i can tell you all where I took the pinion from

(in reply to Mr Hover)
       Post #: 37

RE: zoom 400 tail gear problem - 6/15/2004 1:53:39 PM   
jbalat



Posts: 269
Joined: 3/3/2004
From: MelbourneVictoria, AUSTRALIA
Status: offline 		I dont think it is so much the gearing ratio althought there is no doubt you can easily reduce the load by playing around with this, there is also a lot of merit in using a tougher material for the gear.

However, I dont like the fact the when you try to manually turn the tail rotor it has to turn the motor and main rotor which is quite a heavy load. You can almost feel the teeth breaking off when you do this.

Correct me if I am wrong but I believe the nitro helis would probably have a clutch/one way gear/ or something which would relieve these loads from the tail gear. Without complicating the design, a simple fix may be to replace the heavy duty carbon shaft with a thin piano wire rod which has a lot less torsional rigidity. This would allow the shaft to flex and take up any impulse loads.

(in reply to jinsincity)
       Post #: 38

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