Why no ball bearings in our jet wheels??
11-25-2004, 09:04 AM
#1
Thread Starter
Why no ball bearings in our jet wheels??
Most of the jet wheels I've seen and owned except for Airworlds L39 and Cougar/Panther wheels have bronze bushings. If the tolerances are not 100% accurate between the axle and bushing and they are properly lubricated they tend to become sloppy and wear out very quickly. Not a big cost, but it is very annoying if you don't have spares on your hand.
Is there a reason why ball bearings are not more commonly used, or have I missed something?. I mean... It can't be the cost since ball bearings are cheap and we pay like 150- 250$ for two main wheels with brakes. If you buy a RTR RC car for 150$, you get lots of ball bearings or a Raptor 30 heli, you get something like 39 BB's.
So what is the reason?? Someone please enlighten me....
Is there a reason why ball bearings are not more commonly used, or have I missed something?. I mean... It can't be the cost since ball bearings are cheap and we pay like 150- 250$ for two main wheels with brakes. If you buy a RTR RC car for 150$, you get lots of ball bearings or a Raptor 30 heli, you get something like 39 BB's.
So what is the reason?? Someone please enlighten me....
11-25-2004, 09:14 AM
#3
Thread Starter
RE: Why no ball bearings in our jet wheels??
Really?
Ball bearings are used on full size planes, and imagine the the beating they take on both RC and full size cars.... Like if you crash a heli into the ground, the 1/2 inch shaft are bent like it was butter, but the shaft bearings are normally OK.....
Ball bearings are used on full size planes, and imagine the the beating they take on both RC and full size cars.... Like if you crash a heli into the ground, the 1/2 inch shaft are bent like it was butter, but the shaft bearings are normally OK.....
11-25-2004, 10:12 AM
#4
Join Date: Nov 2003
Location: Curitiba, Parana, BRAZIL
Posts: 4,289
Likes: 0
Received 14 Likes
on
11 Posts
RE: Why no ball bearings in our jet wheels??
Perhaps because they are not needed at all, they are more weight and would turn the already expensive jet wheels more expensive.. At least for me I didn´t had a issue with the bushings in
the bvm wheels, only with the tires that wear out rather quickly and I guess that this is unavoidable....
Rgds, Enrique
the bvm wheels, only with the tires that wear out rather quickly and I guess that this is unavoidable....
Rgds, Enrique
11-25-2004, 10:47 AM
#5
Senior Member
Join Date: Dec 2001
Location: Milton,
ON, CANADA
Posts: 972
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
Hi Staale
I think there are a couple of reasons why you won't find ball bearings on most wheels:
1) They would have to be sealed bearing in order to prevent dirt from getting into the grease and plugging up the bearing.
2) They are more expensive to purchase and would increase the cost of the wheel brakes.
3) They don't provide any decisive advantage over the bushing that are currently being using.
Not withstanding the above, I think you'll find wheels bearings in some of the larger planes in Europe because bushings just wouldn't be able to cope with some of the loads.
My $.02 CDN, now almost worth $.02 US!
Ed
I think there are a couple of reasons why you won't find ball bearings on most wheels:
1) They would have to be sealed bearing in order to prevent dirt from getting into the grease and plugging up the bearing.
2) They are more expensive to purchase and would increase the cost of the wheel brakes.
3) They don't provide any decisive advantage over the bushing that are currently being using.
Not withstanding the above, I think you'll find wheels bearings in some of the larger planes in Europe because bushings just wouldn't be able to cope with some of the loads.
My $.02 CDN, now almost worth $.02 US!
Ed
11-25-2004, 11:10 AM
#6
My Feedback: (14)
Join Date: Apr 2002
Location: St. Mary\'s City,
MD
Posts: 524
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
ORIGINAL: SAP_2000
Really?
Ball bearings are used on full size planes, and imagine the the beating they take on both RC and full size cars.... Like if you crash a heli into the ground, the 1/2 inch shaft are bent like it was butter, but the shaft bearings are normally OK.....
Really?
Ball bearings are used on full size planes, and imagine the the beating they take on both RC and full size cars.... Like if you crash a heli into the ground, the 1/2 inch shaft are bent like it was butter, but the shaft bearings are normally OK.....
11-25-2004, 11:49 AM
#7
Thread Starter
RE: Why no ball bearings in our jet wheels??
ORIGINAL: Chris True
I'm not sure what full scale planes use but I'd be surprised if they were ball bearings. Cars use roller bearings - much wider contact area to take the load. In heli's yes, sometimes they are OK and sometimes not but the bearing is spinning when you hit the ground. With an aircraft wheel about to land the wheel is not spinning and all the load hits on the microscopic contact points of a couple of balls.
I'm not sure what full scale planes use but I'd be surprised if they were ball bearings. Cars use roller bearings - much wider contact area to take the load. In heli's yes, sometimes they are OK and sometimes not but the bearing is spinning when you hit the ground. With an aircraft wheel about to land the wheel is not spinning and all the load hits on the microscopic contact points of a couple of balls.
11-25-2004, 12:01 PM
#8
Thread Starter
RE: Why no ball bearings in our jet wheels??
ORIGINAL: rcav8tr
1) They would have to be sealed bearing in order to prevent dirt from getting into the grease and plugging up the bearing.
2) They are more expensive to purchase and would increase the cost of the wheel brakes.
3) They don't provide any decisive advantage over the bushing that are currently being using.
1) They would have to be sealed bearing in order to prevent dirt from getting into the grease and plugging up the bearing.
2) They are more expensive to purchase and would increase the cost of the wheel brakes.
3) They don't provide any decisive advantage over the bushing that are currently being using.
Advantage would be that they are tighter and roll easier than bushings.
I don't buy the part about the cost.... Let's say you would need two sealed bearings pr. main wheel, it would take four bearings for the mains. Don't know exactly what four say 6*15*6 mm sealed bearings would cost if bought in large quantities, but something like 10-15$?? The price can't be high since you get dozen of them on a 150$ RTR RC car....
11-25-2004, 12:57 PM
#9
Senior Member
Join Date: Dec 2001
Location: Milton,
ON, CANADA
Posts: 972
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
Hi Staale
I agree that they would roll easier, but how much easier do they have to be then bushings?
That's $10-$15 versus $1-$2 or less for bushings! The bearings on a 5lb rc car are not the same as those you'd need on a 25+lb jet. Remember, the car has a suspension system, while most jets do not.
One other point, your axle to bearing inner race tolerance would have to be tight enough to prevent the inner race from spinning on the axle. So your axles would now have to be made to a tighter tolerance which again would drive up the cost. Based on the different axle sizes and qualities I've seen while selling the Trim Wheels and Brakes, I'd stick to the bushings.
Ed
I agree that they would roll easier, but how much easier do they have to be then bushings?
That's $10-$15 versus $1-$2 or less for bushings! The bearings on a 5lb rc car are not the same as those you'd need on a 25+lb jet. Remember, the car has a suspension system, while most jets do not.
One other point, your axle to bearing inner race tolerance would have to be tight enough to prevent the inner race from spinning on the axle. So your axles would now have to be made to a tighter tolerance which again would drive up the cost. Based on the different axle sizes and qualities I've seen while selling the Trim Wheels and Brakes, I'd stick to the bushings.
Ed
ORIGINAL: SAP_2000
Advantage would be that they are tighter and roll easier than bushings.
I don't buy the part about the cost.... Let's say you would need two sealed bearings pr. main wheel, it would take four bearings for the mains. Don't know exactly what four say 6*15*6 mm sealed bearings would cost if bought in large quantities, but something like 10-15$?? The price can't be high since you get dozen of them on a 150$ RTR RC car....
Advantage would be that they are tighter and roll easier than bushings.
I don't buy the part about the cost.... Let's say you would need two sealed bearings pr. main wheel, it would take four bearings for the mains. Don't know exactly what four say 6*15*6 mm sealed bearings would cost if bought in large quantities, but something like 10-15$?? The price can't be high since you get dozen of them on a 150$ RTR RC car....
11-25-2004, 01:35 PM
#10
Thread Starter
RE: Why no ball bearings in our jet wheels??
I see your points Ed, and thanks for your reply!
However, I'd be willing to pay the extra $$ to get BB's on my wheels for two resons... 1. Is to have a tighter and more accurate wheel setup, and 2. so I would not have to keep spare bushings and exchange them so often.
I have mainly used two brands of wheels on my jets, and had to exchange the bushing several times pr. year on both brands. The Model Mechanics brakes with the O-ring pushing outwards against the rim tend to let the air out when the wheel bushings wear out and the wheel can tilt slightly from side to side. When this happens you have no brakes at all. On the runways I normally fly from there is not enough space for the plane to come to a stop without brakes and the result of a brake failiure can easely result in a more or less damaged jet.
There may be differences in quality and tolerances from brand to brand making some wear out more quickly than the other though...?
However, I'd be willing to pay the extra $$ to get BB's on my wheels for two resons... 1. Is to have a tighter and more accurate wheel setup, and 2. so I would not have to keep spare bushings and exchange them so often.
I have mainly used two brands of wheels on my jets, and had to exchange the bushing several times pr. year on both brands. The Model Mechanics brakes with the O-ring pushing outwards against the rim tend to let the air out when the wheel bushings wear out and the wheel can tilt slightly from side to side. When this happens you have no brakes at all. On the runways I normally fly from there is not enough space for the plane to come to a stop without brakes and the result of a brake failiure can easely result in a more or less damaged jet.
There may be differences in quality and tolerances from brand to brand making some wear out more quickly than the other though...?
11-25-2004, 02:18 PM
#11
My Feedback: (145)
RE: Why no ball bearings in our jet wheels??
Hi, BB are just not needed in our application. Bronze bushings are more than fine for what we need. The one point you are not seeing is the great increase in machining costs. With a bushing all you need is a reamed hole of the proper size from one side to the other. If you start with BB then you are going to need to MACHINE a tight tolerance bearing retainer in both sides of the wheel. You just added 10 minutes of expensive machine shop time to the price of the wheel. I also suspect that you would need a fairly large diameter (15-20 mm OD) bearing to take the loads that we abuse or gear to. This might cause some design problems with the wheel. Scott
11-25-2004, 03:24 PM
#12
Senior Member
Join Date: Dec 2001
Location: Milton,
ON, CANADA
Posts: 972
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
Hi Staale
I'm not sure what the other brand of brakes your using is, but it sounds like the Model Mechanics brakes are using a soft bushing material if your changing them more than once per year. I've only had a couple of customers change the bushings on their Trim brakes in the last three years and i've sold quite a few sets.
Ed
I'm not sure what the other brand of brakes your using is, but it sounds like the Model Mechanics brakes are using a soft bushing material if your changing them more than once per year. I've only had a couple of customers change the bushings on their Trim brakes in the last three years and i've sold quite a few sets.
Ed
ORIGINAL: SAP_2000
I see your points Ed, and thanks for your reply!
However, I'd be willing to pay the extra $$ to get BB's on my wheels for two resons... 1. Is to have a tighter and more accurate wheel setup, and 2. so I would not have to keep spare bushings and exchange them so often.
I have mainly used two brands of wheels on my jets, and had to exchange the bushing several times pr. year on both brands. The Model Mechanics brakes with the O-ring pushing outwards against the rim tend to let the air out when the wheel bushings wear out and the wheel can tilt slightly from side to side. When this happens you have no brakes at all. On the runways I normally fly from there is not enough space for the plane to come to a stop without brakes and the result of a brake failiure can easely result in a more or less damaged jet.
There may be differences in quality and tolerances from brand to brand making some wear out more quickly than the other though...?
I see your points Ed, and thanks for your reply!
However, I'd be willing to pay the extra $$ to get BB's on my wheels for two resons... 1. Is to have a tighter and more accurate wheel setup, and 2. so I would not have to keep spare bushings and exchange them so often.
I have mainly used two brands of wheels on my jets, and had to exchange the bushing several times pr. year on both brands. The Model Mechanics brakes with the O-ring pushing outwards against the rim tend to let the air out when the wheel bushings wear out and the wheel can tilt slightly from side to side. When this happens you have no brakes at all. On the runways I normally fly from there is not enough space for the plane to come to a stop without brakes and the result of a brake failiure can easely result in a more or less damaged jet.
There may be differences in quality and tolerances from brand to brand making some wear out more quickly than the other though...?
11-25-2004, 09:00 PM
#13
Senior Member
My Feedback: (6)
Join Date: Jan 2002
Location: Spring Lake,
MI
Posts: 308
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
I find that the bushings do wear out eventually. No biggie to replace them though. I find keeping the axles well greased is essential for good bearing performance.
Tires are also a wear item. That's part of the hobby.
I've used BVM and Intairco wheels and brakes.
I also run RC cars and trucks. A huge difference is that the suspension and soft tires are much more compliant on them than on our jets. Also, the environment for rc cars and trucks is quite dirty and dusty requiring the use of sealed bearings; bushings wouldn't work well in such a dirty environment. Also, I have to imagine that the shock loads, at the bearings, are quite a bit larger for our jets than the rc cars and trucks. Sealed angular roller bearings would probably be a must in our jets. Without checking into it, I would guess that the width of the wheel hubs would need to increase substantially to fit a pair of roller bearings & seals in = added weight, complexity and cost . . .
Bottom line is that although wheel bearings would provide a few features that bushings cannot, I believe bushings are a very effective solution for our application.
Tires are also a wear item. That's part of the hobby.
I've used BVM and Intairco wheels and brakes.
I also run RC cars and trucks. A huge difference is that the suspension and soft tires are much more compliant on them than on our jets. Also, the environment for rc cars and trucks is quite dirty and dusty requiring the use of sealed bearings; bushings wouldn't work well in such a dirty environment. Also, I have to imagine that the shock loads, at the bearings, are quite a bit larger for our jets than the rc cars and trucks. Sealed angular roller bearings would probably be a must in our jets. Without checking into it, I would guess that the width of the wheel hubs would need to increase substantially to fit a pair of roller bearings & seals in = added weight, complexity and cost . . .
Bottom line is that although wheel bearings would provide a few features that bushings cannot, I believe bushings are a very effective solution for our application.
11-25-2004, 10:05 PM
#14
My Feedback: (21)
Join Date: Aug 2002
Location: Los Angeles
Posts: 864
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
ORIGINAL: SAP_2000
I get your point about the shock and small contact area Chris. I'm no mechanic, but the two cars I have changed the wheel bearings on (Audi S2 and BMW 328) both had ball bearings, not roller bearings. They were kind of special bearings with two rows of ''tracks'' in each bearing.
ORIGINAL: Chris True
I'm not sure what full scale planes use but I'd be surprised if they were ball bearings. Cars use roller bearings - much wider contact area to take the load. In heli's yes, sometimes they are OK and sometimes not but the bearing is spinning when you hit the ground. With an aircraft wheel about to land the wheel is not spinning and all the load hits on the microscopic contact points of a couple of balls.
I'm not sure what full scale planes use but I'd be surprised if they were ball bearings. Cars use roller bearings - much wider contact area to take the load. In heli's yes, sometimes they are OK and sometimes not but the bearing is spinning when you hit the ground. With an aircraft wheel about to land the wheel is not spinning and all the load hits on the microscopic contact points of a couple of balls.
11-26-2004, 04:21 AM
#15
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: Why no ball bearings in our jet wheels??
All new Skymaster Main wheels will be supplied with ball bearings.
I am using a set in my hawk and I can really notice the difference. The whole model rolls smoother and easier than any wheels I have had before. (Apart from my large airworld L-39 which is also ballraced)
The only problem I for see is that flying from a dusty (Gravel) field these bearings do need regular cleaning.
By the way sap 2000 did you ever get the 3rd set of axles and bushes I sent?
I am using a set in my hawk and I can really notice the difference. The whole model rolls smoother and easier than any wheels I have had before. (Apart from my large airworld L-39 which is also ballraced)
The only problem I for see is that flying from a dusty (Gravel) field these bearings do need regular cleaning.
By the way sap 2000 did you ever get the 3rd set of axles and bushes I sent?
11-26-2004, 07:32 AM
#16
Thread Starter
RE: Why no ball bearings in our jet wheels??
That is good news Ali!
What does the ball raced rims cost alone, and do the match up with the older style tires and brakes?
And yes, I got them last week. Thank you so much for that!!
Unfortunately it has been poring down with snow here now for the last week, so no flying for me until melts away again or the lakes freezes....[:@]
What does the ball raced rims cost alone, and do the match up with the older style tires and brakes?
And yes, I got them last week. Thank you so much for that!!
Unfortunately it has been poring down with snow here now for the last week, so no flying for me until melts away again or the lakes freezes....[:@]
11-26-2004, 08:50 AM
#17
Senior Member
Join Date: Jan 2003
Location: Sydney, AUSTRALIA
Posts: 244
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
Shock loads? With a rubber tyre? I don't think there are substantial shock loads in our wheels - certainly not enough to damage ball races which are sized correctly. About 10 years ago I had a Cressline F20 which weighed 15lb RTF. It had 2 3/4" mains and would take about 250m on grass to takeoff (about the full length of our strip. I had an idea - machine up wheel hubs with ball races. I did this and it cut the takeoff run in half, literally. I don't know why more people don't do it.
11-26-2004, 10:42 AM
#18
Senior Member
My Feedback: (1)
Join Date: Jan 2002
Location: West Linda,
CA
Posts: 415
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
Number one reason is cost - we offered ball bearings for about 7 years in all of our wheels, and when given the option, they would almost always opt for the cheaper option.
I just checked the last 2 years that we offered them, and there were only 2 sets of wheels shipped with B-bearings (with the exception of RPV wheels in which they are standard)
Dennis
I just checked the last 2 years that we offered them, and there were only 2 sets of wheels shipped with B-bearings (with the exception of RPV wheels in which they are standard)
Dennis
11-27-2004, 12:22 PM
#19
Junior Member
Join Date: Nov 2004
Location: Järvenpää, FINLAND
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
RE: Why no ball bearings in our jet wheels??
I have used b-bearings in my Hornet last five years. A lot of spanking and they are still like new. Only problem is that I need to use brakes a lot. Plane just likes to roll around.
11-29-2004, 03:47 AM
#20
RE: Why no ball bearings in our jet wheels??
Staale
At the JetPower meet in Germany, there was this guy Erwin Tratz of Airtech Germany, showing all his Rims/Tires/Brakes and L/G.
I ended up buying a set of main wheels for my Avonds F-16. Dual ball bearing, very light at a reasonable price with ample of spares available and your choice of axle dia. (I´m beefing the std. gear up to 6mm)
[img][/img]
[link]http://airtech-germany.de[/link]
BRG
Thomas
At the JetPower meet in Germany, there was this guy Erwin Tratz of Airtech Germany, showing all his Rims/Tires/Brakes and L/G.
I ended up buying a set of main wheels for my Avonds F-16. Dual ball bearing, very light at a reasonable price with ample of spares available and your choice of axle dia. (I´m beefing the std. gear up to 6mm)
[img][/img]
[link]http://airtech-germany.de[/link]
BRG
Thomas
11-29-2004, 05:39 AM
#21
My Feedback: (5)
Join Date: Apr 2002
Location: Northamptonshire , UNITED KINGDOM
Posts: 4,994
Likes: 0
Received 18 Likes
on
17 Posts
RE: Why no ball bearings in our jet wheels??
Hi Staale
If you wanted just the wheels let me know and I will work something out for you.
It has to be the worst thing waiting for the weather to clear to play with your new toy.
If you wanted just the wheels let me know and I will work something out for you.
It has to be the worst thing waiting for the weather to clear to play with your new toy.
11-29-2004, 03:00 PM
#22
Thread Starter
RE: Why no ball bearings in our jet wheels??
Thank you all very much for your replies and views on this subject!
A321:
wheels look very good! What brake system do they use?
Ali:
Thanks for the info. I have a good stock off spare bushings for now, but I will definitely switch to ball bearings when my spares run out. I'll contact you later.
A321:
wheels look very good! What brake system do they use?
Ali:
Thanks for the info. I have a good stock off spare bushings for now, but I will definitely switch to ball bearings when my spares run out. I'll contact you later.
