Author Topic: another stupid question - ref where to put a disc brake  (Read 412 times)

Tinworm

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This will probably be blinkin obvious, but if you have a live, driven axle, does it make the slightest bit of difference where, along the axle, you put your brake disc?

I know this may seem an absurd question (I know I'd think so if someone else asked it) but can the kart slew sideways if the shaft is grabbed at the end rather than in the middle, or does it make no difference at all because the shaft is the shaft is the shaft....all the way along its length?
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

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Chris L

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Re: another stupid question - ref where to put a disc brake
« Reply #1 on: 16 Apr 22, 11:23 pm »
That's a perfectly reasonable question Peter.


 Firstly,  are you having both rear wheels Driven ; ie locked onto the the axle ?

Chris L

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #2 on: 16 Apr 22, 11:26 pm »
That's a perfectly reasonable question Peter.


 Firstly,  are you having both rear wheels Driven ; ie locked onto the the axle ?

Chris L

ah, well since asking, I have been wondering about that. I know that they are easier to steer if only one wheel is driven, but until today I thought I was going to do a live axle with both wheels driven, but I am thinking of maybe making it just one. What do you think? And how will that affect braking?
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

jim

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Re: another stupid question - ref where to put a disc brake
« Reply #3 on: 17 Apr 22, 06:30 am »
You will get a much shorter braking distance if your braking on both rear wheels because it's tyre contact that is the limiting factor. Well it is if you have a good disc/calliper and master cyl set up. Then when your hurtling round a track at the death defying speeds a poxy little 6.5hp cement mixer engine will carry you, you do Scandinavian flicks old bean.  ;D
If you can drive round corners, you're not going fast enough.

ChrisS

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Re: another stupid question - ref where to put a disc brake
« Reply #4 on: 17 Apr 22, 08:04 am »
Back to the original question, I can't see why it would make any difference where you put it, irrespective of how many driven wheels. I suppose there might be some torsional twist in the axle, but not enough to be noticeable.

Jimr1999

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Re: another stupid question - ref where to put a disc brake
« Reply #5 on: 17 Apr 22, 08:08 am »
Would the brake mounting point move with the axle to prevent the pads being out of line with the tilt of the disc?
... You can lead a horse to water, but a pencil must be lead.

Jimr1999

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Re: another stupid question - ref where to put a disc brake
« Reply #6 on: 17 Apr 22, 09:55 am »
...with a rose joint back to the frame like so...
... You can lead a horse to water, but a pencil must be lead.

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #7 on: 17 Apr 22, 11:32 am »
Would the brake mounting point move with the axle to prevent the pads being out of line with the tilt of the disc?

What tilt do you anticipate?

and that graphic - how quickly did you generate it? I really must look into CAD. I used it at college in 1990, when it was a real faff (two monitors, lots of code), but I gather it is user friendly now?
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

Jimr1999

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Re: another stupid question - ref where to put a disc brake
« Reply #8 on: 17 Apr 22, 11:47 am »
The CAD "package" I used is just a basic online thing made by Autocad for educational use to wean prospective engineers towards its products. It is very basic but uses some of the functions of Autocad Inventor.
www.tinkercad.com
With a little familiarisation and learning the shortcuts and controls, it is not too difficult to get the hang of. Inventor is more accurate but for quick sketches it will do. Online tutorials abound. I use it to introduce my students to CAD.
The angles you could get on a sprung axle could be different to the frame when cornering, going over camber or bumps. If this would effect adversely the brake I do not know as most brake set ups seem to travel with the axle, not the frame.
... You can lead a horse to water, but a pencil must be lead.

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #9 on: 17 Apr 22, 12:12 pm »

www.tinkercad.com
With a little familiarisation and learning the shortcuts and controls, it is not too difficult to get the hang of.

Thanks , I have been having a play. very distracting. One for when I can't go to the shed
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #10 on: 17 Apr 22, 12:21 pm »
...with a rose joint back to the frame like so...

rose jointing for flexibility. hmmm hadn't thought of that.

But as regards where to brake the axle, does it make a difference where along its length?
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #11 on: 17 Apr 22, 12:23 pm »
Back to the original question, I can't see why it would make any difference where you put it, irrespective of how many driven wheels. I suppose there might be some torsional twist in the axle, but not enough to be noticeable.

Good, that is what I thought - and hoped. Cheers
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #12 on: 17 Apr 22, 12:25 pm »
You will get a much shorter braking distance if your braking on both rear wheels because it's tyre contact that is the limiting factor.

yes, in the braking versus steering calculation, which is better, altogether, two driven wheels or one?
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter

Chris L

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Re: another stupid question - ref where to put a disc brake
« Reply #13 on: 17 Apr 22, 01:24 pm »
Hi Peter, As Chris S and Jim have stated.
 At our level on a solid axle;  it doesn't matter where the Disc/caliper assembly is mounted.  This is usually decided and fitted to one side because Engine / Drive assembly takes the bulk of the room.

With one wheel braked (Hub not locked both sides) you will lock the braked wheel under heavy braking (as long as you have an effective Hydraulic system) , which can be a little unnerving . This improves as as everything warms up.
 I ran this set up all last year, and as you rightly stated you do benefit from tighter turn in.

With both Hubs locked / two wheel braking / two driving; It probably feels more stable under braking , as braking is distributed more evenly across the axle and less likely to lock wheels .

Chris L

Tinworm

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Re: another stupid question - ref where to put a disc brake
« Reply #14 on: 17 Apr 22, 03:51 pm »
I suppose the tighter, more positive steering is the more desirable quality, so have one rear wheel free-wheeling?
I don't want to bore you all with the details, here. But if you are interested, have a look at my blog https://peteskart.blogspot.com/

-Peter