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Old 11-30-2011, 01:46 PM   #16
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Originally Posted by keithlaw View Post
1) What is the "end load"?
2) When end load required to ensure the diff doesn't slip is lower, what is the advantage of that??
3) What is a cone washers? Is that the one came with the F104 assembly kit??

Sorry, I have too many questions. I a not very familiar with ball diff.
The end load is the load you apply to the diff assembly by tightening the nut on the end of the axle. The nut screws on to some cone-shaped washers that provide a 'spring' between the nut and the bearing. That's what a 12th diff uses, maybe a Tamiya diff is... er... different?!!

The ball diff works by allowing one wheel to rotate relative to the other when there is a differential speed between one wheel and the other. In order to do that, one wheel is allowed to revolve independently between two thrust races - one on the gear and one on the hub.

For the motor to get drive to the rear axle, the torque is transmitted from the spur gear, through the balls to the large thrust races either side of the spur gear. One washer is connected to the left-hand wheel through the axle, and the other to the right hand wheel through the hub.

In order to take the torque of the motor, the thrust race must have enough load on it to create friction that allows the ball to grip on the thrust race. If there is not enough friction, then the ball will slip on the thrust race. The load is created when you tighten the nut on the end of the axle, and themore you tighten the nut, the more you increase the load until you have enough load to create enough friction that the gear does not slip when the motor torque is applied.

If you can create that friction with a lower end load, then the diff runs freer and gives more life and better handling. Because the balls in the radial bearing are smaller (pressure (load) = force x area) and create more friction for the same end load than a thrust race, you need less end load and therefore you get better diff performance as the diff is freer than an diff with a thrust race. HTH
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Old 01-05-2015, 10:48 PM   #17
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Default Radial load chance in the ball diff

When the one wheel getting struck stage, rotation in the other wheels not stopped in the car. So radial load is same.
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Old 01-06-2015, 01:08 AM   #18
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Quote:
Originally Posted by SlowerOne View Post
The end load is the load you apply to the diff assembly by tightening the nut on the end of the axle. The nut screws on to some cone-shaped washers that provide a 'spring' between the nut and the bearing. That's what a 12th diff uses, maybe a Tamiya diff is... er... different?!!

The ball diff works by allowing one wheel to rotate relative to the other when there is a differential speed between one wheel and the other. In order to do that, one wheel is allowed to revolve independently between two thrust races - one on the gear and one on the hub.

For the motor to get drive to the rear axle, the torque is transmitted from the spur gear, through the balls to the large thrust races either side of the spur gear. One washer is connected to the left-hand wheel through the axle, and the other to the right hand wheel through the hub.

In order to take the torque of the motor, the thrust race must have enough load on it to create friction that allows the ball to grip on the thrust race. If there is not enough friction, then the ball will slip on the thrust race. The load is created when you tighten the nut on the end of the axle, and themore you tighten the nut, the more you increase the load until you have enough load to create enough friction that the gear does not slip when the motor torque is applied.

If you can create that friction with a lower end load, then the diff runs freer and gives more life and better handling. Because the balls in the radial bearing are smaller (pressure (load) = force x area) and create more friction for the same end load than a thrust race, you need less end load and therefore you get better diff performance as the diff is freer than an diff with a thrust race. HTH
Sorry. Thats tosh. There is no reason to use a normal radial bearing in place of a thrust bearing in a diff, as you are loading the bearing in a way that it is not intended (side loading).

Ask any competitive F1 driver, and the best update you can make to a Tamiya F1 diff is getting rid of the radial bearing (which is only included on grounds of cost), and replacing it with a thust, along with going to ceramic diff balls.
A thrust bearing will give a far more relaible and consistent diff, and given the diff is a massive factor on the performance of any pan car (after all the drive only goes through the rear wheels), its one of the best and cheapest upgrades for an F1. End of.
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Old 01-06-2015, 04:28 AM   #19
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I don't know about the Tamiya diff but I do know about the original VBC 04. It came with a thrust bearing diff but it was completely useless. The reason why was the inner plate that the thrust bearing rolled on applied the force directly to the inner race of the outer diff hub radial bearing anyway. If Tamiya does it differently then they would have an advantage in that area. I am a retired ME and I have searched the bearing manufacturers for a thrust bearing that is A. small enough on the O.D. to fit in the diff hub and B. has a ball path or a race that would apply the thrust force to the outer race of the radial bearing. The other option is a high angle, angular contact ball bearing. These bearings have higher thrust ratings than the bearing we currently run. So far no luck there either. I am not dedicating my life to this search but if someone out there can solve the problem then it would be very marketable to a small crowd.
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Old 01-06-2015, 08:58 AM   #20
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The two versions of the Tamiya F1 cars linked on the previous page have the same shortcoming, i.e. the side load is applied to a radial bearing. One setup (the F104) does include a thrust bearing but this in turn pushes against a radial bearing, not clear if it pushes against the outer or inner race (outer end of diff housing A - part BG3). One could potentially rectify the problem by using a tiny washer or collar/ring between the thrust and the radial that would ensure the thrust bearing pushes against the outer race of the radial.

I would use an outer race of a bearing the same size as the radial, cut and ground to appropriate size.
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Old 01-06-2015, 12:26 PM   #21
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Sorry. Thats tosh. There is no reason to use a normal radial bearing in place of a thrust bearing in a diff, as you are loading the bearing in a way that it is not intended (side loading).

Ask any competitive F1 driver, and the best update you can make to a Tamiya F1 diff is getting rid of the radial bearing (which is only included on grounds of cost), and replacing it with a thust, along with going to ceramic diff balls.
A thrust bearing will give a far more relaible and consistent diff, and given the diff is a massive factor on the performance of any pan car (after all the drive only goes through the rear wheels), its one of the best and cheapest upgrades for an F1. End of.
Oh dear, oh dear - a lack of mechanical understanding there!

If the F1 diff is as described by the later posters, and uses both a thrust and the inner race of the radial bearing, then no wonder is doesn't work!

If as you so boldly state, my analysis is rubbish, then explain why there is no top driver in a Worlds A Final using a thrust race in place of the roller bearing. Would that be because the thrust race has scrub and is not as free as the roller bearing? Oh yes!

There is only one diff I have ever seen that works as well using a thrust race and that is the Zen one. I have converted a few 12th drivers away from other thrust bearings to using the roller bearing and every one of them comes back to me and says their car handles now. The only thing we agree on here is that the diff is key to handling!

If your analysis is based on a poor diff design it is in itself tosh. Nonetheless I do know what it is like to be in the majority of one! The mechanical engineering principles of my explanation are sound.

PS - if you think that the roller bearing is not designed to take a side load, why are you using them as axle bearings? The side loads in cornering are high too, especially when you tap a board, so do you have thrust races on each side of the axle bearings to take that load. I thought not...
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Old 01-06-2015, 12:44 PM   #22
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Originally Posted by SlowerOne View Post
Oh dear, oh dear - a lack of mechanical understanding there!

If the F1 diff is as described by the later posters, and uses both a thrust and the inner race of the radial bearing, then no wonder is doesn't work!

If as you so boldly state, my analysis is rubbish, then explain why there is no top driver in a Worlds A Final using a thrust race in place of the roller bearing. Would that be because the thrust race has scrub and is not as free as the roller bearing? Oh yes!

There is only one diff I have ever seen that works as well using a thrust race and that is the Zen one. I have converted a few 12th drivers away from other thrust bearings to using the roller bearing and every one of them comes back to me and says their car handles now. The only thing we agree on here is that the diff is key to handling!

If your analysis is based on a poor diff design it is in itself tosh. Nonetheless I do know what it is like to be in the majority of one! The mechanical engineering principles of my explanation are sound.

PS - if you think that the roller bearing is not designed to take a side load, why are you using them as axle bearings? The side loads in cornering are high too, especially when you tap a board, so do you have thrust races on each side of the axle bearings to take that load. I thought not...
Yeah, but no.

You didn't explain anything new for most kindergarten graduates and you got your formula for pressure wrong as well (fifth grade stuff) pressure=force/area (measuring units are a dead giveaway - Newton/square metre = Pascal).

Quote:
Originally Posted by SlowerOne View Post

[...]

Because the balls in the radial bearing are smaller (pressure (load) = force x area) and create more friction for the same end load than a thrust race, you need less end load and therefore you get better diff performance as the diff is freer than an diff with a thrust race. HTH
The side load due to cornering on wheel bearings is next to nothing normally. If you hit a board you can bet your first born your wheel bearing is gone too. We use them there because we need to keep the axles centered, though I agree, there should be a thrust bearing to take the impacts, but that would over complicate the design of hubs no end. Taper roller bearings like in real cars would be ideal. It's a matter of cost.

Not to mention the two don't really compare because one is progressive, the other more like hammer hit.

By the way, you're talking about roller bearings which are something else again, we don't have roller bearings on wheels.

The reason examples like those linked don't work is explained in my post above. But those are not the only existing designs.

Using ball bearings is a pain in the proverbial because they are pinched way too easily giving very little adjustment range.

Oh, and by the way, the thrust bearings we use usually have smaller balls than axial bearings so your logic is wrong there too. Not to mention that's a very gross approximation. Bearings can have different sized balls for the same size bearing. Not that it makes any difference anyway. On the contrary, if anything smaller balls will apply higher pressures because of the smaller area of contact (see the CORRECT equation above).

You might be in a majority of one for a good reason, after all.
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Old 01-06-2015, 01:02 PM   #23
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With a F1 and any other pancar rear end with a diff on a solid axle the diff needs some axial pressure to prevent slip and more tension to make the dif tighter.The pressure is done from the side of the wheelhub. The right wheelhub is running on normal bearings so it spins free fron the solid axle connected to the left rear wheel. Only a normal bearing is not made to handle the axial force needed to geve the diff the right tension. To keep the 2 wheels running independend the pressure on a normal bearing is needed on the inner brace of the bearing and through the balls tranfered to the outer brace to get the force on the diff, the bearing will fail.
A larger pressure plate touching the outside brace of the bearing could fix it but it will give a binding of the wheelhub on the shaft. But with 2 larger plates and some balls in between you can make the needed pressure without a binding.

There are bearings with L-shaped braces which do combine a radial and axial bearing in one:
http://sktbearing.en.alibaba.com/pro...F_2575_TN.html, they can also be found in our sizes.
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Old 01-06-2015, 01:17 PM   #24
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Originally Posted by Roelof View Post
With a F1 and any other pancar rear end with a diff on a solid axle the diff needs some axial pressure to prevent slip and more tension to make the dif tighter.The pressure is done from the side of the wheelhub. The right wheelhub is running on normal bearings so it spins free fron the solid axle connected to the left rear wheel. Only a normal bearing is not made to handle the axial force needed to geve the diff the right tension. To keep the 2 wheels running independend the pressure on a normal bearing is needed on the inner brace of the bearing and through the balls tranfered to the outer brace to get the force on the diff, the bearing will fail.
A larger pressure plate touching the outside brace of the bearing could fix it but it will give a binding of the wheelhub on the shaft. But with 2 larger plates and some balls in between you can make the needed pressure without a binding.

There are bearings with L-shaped braces which do combine a radial and axial bearing in one:
http://sktbearing.en.alibaba.com/pro...F_2575_TN.html, they can also be found in our sizes.
The bearing that comes with the F104 blue aluminium diff set is fantastic. I would never go back to a thrust bearing after using this. And it has lasted at least 3 years of racing now!

I had doubts at first, but the fact is - it works great.
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Old 01-06-2015, 01:20 PM   #25
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The biggest issue is the O.D. of the thrust bearings available (that I have found are to large to fit in the current hubs.
Almost all radial bearings ball have thrust capability as they do not contact on the true od of the ball but actually contact in two points. These bearings are made with different contact patterns to balance their radial to thrust capability. But again there do not appear to be any low angle (high thrust) versions that fit our current axles and hubs.
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Old 01-06-2015, 03:53 PM   #26
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Originally Posted by niznai View Post
The two versions of the Tamiya F1 cars linked on the previous page have the same shortcoming, i.e. the side load is applied to a radial bearing. One setup (the F104) does include a thrust bearing but this in turn pushes against a radial bearing, not clear if it pushes against the outer or inner race (outer end of diff housing A - part BG3)
In the standard F103/F104 diff which has the thrust bearing the thrust bearing presses against the wheel, and therefore the diff housing itself. there is no thrust load on the side of the radial bearing. The disadvantage of this design is that to change wheels you have to disassemble the diff.




Personally in 1/12th I use the radial bearing/cone washer as the diff is much smoother that way. For WGT and F1 I use a thrust bearing purely because it saves on rebuilds as because they are heavier there is more chance of the radial bearing being damaged in an accident. Being less critical than in 1/12th with the bigger tyres there is less difference between the two styles.
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Old 01-06-2015, 04:02 PM   #27
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Originally Posted by SlowerOne View Post
Oh dear, oh dear - a lack of mechanical understanding there!

If the F1 diff is as described by the later posters, and uses both a thrust and the inner race of the radial bearing, then no wonder is doesn't work!

If as you so boldly state, my analysis is rubbish, then explain why there is no top driver in a Worlds A Final using a thrust race in place of the roller bearing. Would that be because the thrust race has scrub and is not as free as the roller bearing? Oh yes!

There is only one diff I have ever seen that works as well using a thrust race and that is the Zen one. I have converted a few 12th drivers away from other thrust bearings to using the roller bearing and every one of them comes back to me and says their car handles now. The only thing we agree on here is that the diff is key to handling!

If your analysis is based on a poor diff design it is in itself tosh. Nonetheless I do know what it is like to be in the majority of one! The mechanical engineering principles of my explanation are sound.

PS - if you think that the roller bearing is not designed to take a side load, why are you using them as axle bearings? The side loads in cornering are high too, especially when you tap a board, so do you have thrust races on each side of the axle bearings to take that load. I thought not...
Calm down turbo.
I've raced many many F1's, and if you doubt my record in the class, 2012 TITC... thanks very much. And guess what, my diff's have always had a thrust race in them (at least the bearing against the diff nut), as it provides as far smoother diff. And that is based on practical experience rather than theory. I suggest you get out of your mechanical theory and build up an F1 diff with both and see which is better.

Your comment about an axle is a different kettle of fish, your not relying on the side load to provide a consistent level of pressure to the balls and plates... and they also aren't sprung loaded.

You can get back onto your soap box now, and await your next outburst... popcorn nom nom nom
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Old 01-06-2015, 04:15 PM   #28
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Originally Posted by terry.sc View Post
In the standard F103/F104 diff which has the thrust bearing the thrust bearing presses against the wheel, and therefore the diff housing itself. there is no thrust load on the side of the radial bearing. The disadvantage of this design is that to change wheels you have to disassemble the diff.

Personally in 1/12th I use the radial bearing/cone washer as the diff is much smoother that way. For WGT and F1 I use a thrust bearing purely because it saves on rebuilds as because they are heavier there is more chance of the radial bearing being damaged in an accident. Being less critical than in 1/12th with the bigger tyres there is less difference between the two styles.
Thats a sensible compromise, and certainly makes more sense. In F1, a normal radial bearing will get notchy and gritty very quickly, as more pressure is needed to avoid diff slip. As you correctly summise the tyres are far far heavier in F1 compared to a 12th. Bit like comparing apples and oranges....
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