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Old Jan 23, 2013, 05:00 PM
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Australia, QLD, Burua
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Originally Posted by davehour View Post
Chris,

Actually, I was thinking about that because I don't have any at the moment. I had to put that new big bore to work after costing me that much, LOL.

Do you think the bike will break even landing the correct way?

What height will be ok to jump without risking the bike?

David
Hey David, with the big bore you can get away with some big flat landings no worries. I just meant if something went wrong where the bike lands nose first or cartwheels badly. Sometimes you can pull the shock end like TJ did. This will break the lower chassis. TJs made some alloy shock ends for sale which will eliminate this issue. The other two things you could break if landing incorrectly especially when doing backflips is the steering stem block which is designed to fail however sometimes the main chassis cracks. If you keep a stem block and main chassis spare and order TJs end you should be right to attack anything.
Ideally yes find a nice bit of slope on a downhill to land as it will land better. If flat landing try not jumping high but long and land rear wheel first slightly.
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Old Jan 23, 2013, 07:32 PM
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Gaz-b, I'm running the stock brass front sprocket.
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Old Jan 23, 2013, 07:50 PM
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Originally Posted by TopDave View Post
motards, I was shreading the knobby too fast!
Cool!
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Old Jan 23, 2013, 09:20 PM
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The brass front sprocket wear out fast, has anybody use a steel front sprocket?
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Old Jan 23, 2013, 11:09 PM
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United States, CA, Vacaville
Joined Oct 2003
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Originally Posted by davehour View Post
Great, thanks!

Are you able to do backflips with it?

How high you can go with them?

David
Back flips? Not intentionally

On those ramps, a full speed run up will launch to low earth orbit. Just below GPS satellites. But you better have a large bowl of Jello to land in if you hit it full speed.

Seriously, you could probably get the bike about 8 feet high. The ramps are not huge which makes them nice and portable. Just a guess but I think they are about 16" high and about 30 inches long. Perfect for every day RC bashing.
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Old Jan 24, 2013, 01:45 AM
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Originally Posted by Jimob23 View Post
Chris
I think you are 100% correct regarding the gyro noise
Have been doing a bit of work balancing the flywheel assisted by an aero mechanic who was able to dynanic balance but only to 10,000 RPM
To give Atomic some credit I think the basic steel section is pretty accurate .
The problem comes when attaching the magnet sections hence the some appear ok and others need attention
Fitted a set of SKF bearings and reduction in the rumbling sound was very noticable
Just need to be aware that with rubber seals the rated RPM is reduced to 20,000 compared to 30,000 for metal shields .Am told the friction heats up the rubber contact area ,hardens it and reduces the seal effect
Price is a big factor so perhaps replacing the Chinese sourced bearing on a regular basis is the way to go
Static balancing is essential to reduce as much vibration as possible since that is an arch enemy of any bearing regardless of place of manufacture
Disregarding of the price factor part ceramc bearings are fine for high RPM static applications but not the best for impact load situations experianced in jumping etc as the balls can shatter .
Fully ceramic are a non starter mainly due to pricing but also the outer ring is not designed to fit into an interferiance fit situation so can crack and again the impact load issue

cheers Jim
I'd have to agree there Jim. Be nice to see them balanced after the magnet fitting.
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Old Jan 24, 2013, 02:14 AM
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The flywheel bearing pockets vary by production batch. As a result if the pocket and bearing have play the flywheel is more noisy. If the pockets are a tight slip fit as specified then the bearings will not slap around in the pockets. The flywheels are not balanced in production but they are CNC machined and the magnets are supposed to be installed by template to keep costs down.
Bottom line if the flywheel is very noisy this is a QC problem and it should be under warranty because its a manufacturing defect.

If you find you have a quiet flywheel then static balance it. The RPM should go up slightly and the noise will be just typical brushless motor sounds. The wheel covers will resonate and amplify the sounds inside.
Also if you want to increase RPM and reduce amps clean the bearings out and use light oil to lubricate them. The factory grease inside is firm and causes drag but once its hot it runs out of the bearings.
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Old Jan 24, 2013, 03:06 AM
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Originally Posted by Chris Nicastro View Post
The flywheel bearing pockets vary by production batch. As a result if the pocket and bearing have play the flywheel is more noisy. If the pockets are a tight slip fit as specified then the bearings will not slap around in the pockets. The flywheels are not balanced in production but they are CNC machined and the magnets are supposed to be installed by template to keep costs down.
Bottom line if the flywheel is very noisy this is a QC problem and it should be under warranty because its a manufacturing defect.

If you find you have a quiet flywheel then static balance it. The RPM should go up slightly and the noise will be just typical brushless motor sounds. The wheel covers will resonate and amplify the sounds inside.
Also if you want to increase RPM and reduce amps clean the bearings out and use light oil to lubricate them. The factory grease inside is firm and causes drag but once its hot it runs out of the bearings.
All makes sense as it is evident the steel section is CNC produced so if perhaps a bit out on sizing overall balance will not be affected
Unsure as to how many are produced daily but like all mass production there will be some % reject expected
Atomik have been excellent in sorting out things for me even out of warranty and also how dull would it be if everything was perfect and no fiddling required
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Old Jan 24, 2013, 04:14 AM
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Originally Posted by Chris Nicastro View Post
The flywheel bearing pockets vary by production batch. As a result if the pocket and bearing have play the flywheel is more noisy. If the pockets are a tight slip fit as specified then the bearings will not slap around in the pockets. The flywheels are not balanced in production but they are CNC machined and the magnets are supposed to be installed by template to keep costs down.
Bottom line if the flywheel is very noisy this is a QC problem and it should be under warranty because its a manufacturing defect.

If you find you have a quiet flywheel then static balance it. The RPM should go up slightly and the noise will be just typical brushless motor sounds. The wheel covers will resonate and amplify the sounds inside.
Also if you want to increase RPM and reduce amps clean the bearings out and use light oil to lubricate them. The factory grease inside is firm and causes drag but once its hot it runs out of the bearings.
It seems like not only the pockets can vary but also the outside diameter of the Chinese bearings causing a similar thing. I try and find the most slop free and tightest fitting for the gyro. They are cheap as and when cleaned and lubed correctly last a long time and run a lot quieter.
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Old Jan 24, 2013, 10:39 AM
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Since on the topic of bearings in flywheel, anyone have a source for replacement bearings for the flywheel that are a good compromise of price and quality that have reduced noise in wheel? Mine are loud but I can live with it until time to replace. Just curious.
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Old Jan 24, 2013, 12:08 PM
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when I rebuilt my flywheel I used some rubber sealed ceramic's and removed the inner seal to further reduce drag although they felt very good this also allowed the excess lube to be thrown out. With the flywheel lying flat fitted them with thread lock to take up any slop in the flywheel machining.
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Old Jan 24, 2013, 12:56 PM
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Originally Posted by chktm View Post
It seems like not only the pockets can vary but also the outside diameter of the Chinese bearings causing a similar thing. I try and find the most slop free and tightest fitting for the gyro. They are cheap as and when cleaned and lubed correctly last a long time and run a lot quieter.
As I mentioned earlier I enlisted some help from an aircraft engineer who very simply explained the problem with Chinese bearings
They are producing very big numbers at very competitive pricing so something has to suffer
Material is one but then tolerances are another and in the higher priced bearings that is what you are paying for .
If you are on good terms with a LHS and they have some stock it may be productive if you measured up the outer sizes and selected the better ones
If you have two sets of large allowed tolerances and the flywheel bore is at the max allowed and bearing the minimum that does not help
Bearing failure is hard to tie down but if the issue is pushed and replacement is offered the cost is considerably less than having to maintain closer tolerances .
I think the same applies to the CNC flywheels where I would say many people live with the noise unaware of the cause
Vibration is a bearing killer so the off balance advances bearings failure and it is presumed water ingress is blamed and so they are replaced non the wiser unless they read about it in a forum such as this

Cheers Jim
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Old Jan 24, 2013, 01:20 PM
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Originally Posted by Gaz-b View Post
when I rebuilt my flywheel I used some rubber sealed ceramic's and removed the inner seal to further reduce drag although they felt very good this also allowed the excess lube to be thrown out. With the flywheel lying flat fitted them with thread lock to take up any slop in the flywheel machining.
Following on from Johnnymac's comment regarding bearings this is interesting possible .
In my investigations I was advised against partial ceramic as the possible impact could fracture the balls
There is still the problem with the steel outer and inner with water etc
Fully ceramic would perhaps get over the water problem but the ceramic outer is not designed to be press in tight fit as for steel outer and can fracture .
As I said will be interesting to hear as to how they stand up and for interest what was the cost of the 3 x ceramic as I was led to believe they talk in telephone numbers regarding price .

cheers Jim
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Old Jan 24, 2013, 01:34 PM
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Originally Posted by wannabe View Post
On those ramps, a full speed run up will launch to low earth orbit. Just below GPS satellites.
Just below? You know gps is placed quite high in medium earth orbit? (being pedantic)

For those interested in ramps and ramp building, ballistic trajectory will give you a good idea of what to expect. This guide from Hyperphysics is quite useful.
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Old Jan 24, 2013, 01:54 PM
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Originally Posted by Jimob23 View Post
Following on from Johnnymac's comment regarding bearings this is interesting possible .
In my investigations I was advised against partial ceramic as the possible impact could fracture the balls
There is still the problem with the steel outer and inner with water etc
Fully ceramic would perhaps get over the water problem but the ceramic outer is not designed to be press in tight fit as for steel outer and can fracture .
As I said will be interesting to hear as to how they stand up and for interest what was the cost of the 3 x ceramic as I was led to believe they talk in telephone numbers regarding price .

cheers Jim
The metal on ceramics tends to be stainless and I have only used them on the flywheel not the road wheels. On the road wheels I have used SS 2rs bearings and fitted them with flowable silicone sealant including the cable entry. I keep upgrading bits I fitted a high torque HV brake servo today and now had to find an alterative to the cable outer as it was collapsing and concertinaring .
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