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Learning how to build Lotus Seven replicas...together!
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PostPosted: May 31, 2015, 5:59 pm 
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I've always been intrigued by the concept of inboard brakes, if only for the reduction of unsprung weight. In the 50s & early 60s, many of the top echelon racing/sports cars used them. Today, almost none! Maybe the problems (heat, serviceability) far outweigh the benefits! I wonder, could the energy from those hot spinning turbines (vented discs) be harnessed in some way to do other work for us. In like manner to a turbo-charger using wasted energy that normally just goes out the exhaust pipe. Something to think about! :?:

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PostPosted: May 31, 2015, 6:11 pm 
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ngpmike wrote:
I wonder, could the energy from those hot spinning turbines (vented discs) be harnessed in some way to do other work for us. In like manner to a turbo-charger using wasted energy that normally just goes out the exhaust pipe. Something to think about! :?:



A spot of tea perhaps?

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PostPosted: May 31, 2015, 6:19 pm 
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Bobber wrote:
Inboards pass all your braking forces through your half shafts, joints, etc. For what that's worth.


I suppose, but when you think the same shafts/joints can cope with side stepping the clutch and lighting up the rear tyres even with the weight transfer of the car on them the braking forces acting on them would be insignificant by comparison.

Bob

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PostPosted: May 31, 2015, 10:18 pm 
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Rear brakes compensate for 30 precent of overall braking correct? On a light car such as a Locost how hot do you think those rear brakes will actually get? If you spaced the rotor out far enough like he is saying shaft seals shouldn't be an issue. Some fancy duct work can do wonders on cooling. Changing rotors wouldn't be fun but it's something worth looking into.

Just my thoughts on the topic.

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PostPosted: May 31, 2015, 10:33 pm 
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Briggs wrote:
Rear brakes compensate for 30 precent of overall braking correct? On a light car such as a Locost how hot do you think those rear brakes will actually get?



VERY HOT! While the car may be lighter but because of that reduced weight it can go faster quicker which means it has a greater speed to shed and people smarter than me say shedding speed trumps mere weight.

I've seen inboards in action on a 7ish vehicle and seals are definitely an issue plus accessiblilty sucks big time! How often do you change your brake pads?

Change them before a track day? It will now be triple or quadruple the time you normally take to do this "little" chore.

Heat build up affects more than just the seals. What's going to be located close to the brakes or right over them? That will be different on most cars, but how will that heat affect whatever's there?

Where are you putting your gas tank? I hope not right over the diff and inboard brakes because that means you can't make a removable access panel to allow you to get to the brakes.

A track only exo-skeleton with unlimited access sounds like an awesome car for inboards, but definitely not the best set up for a dual purpose car or a traditional 7.

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PostPosted: June 1, 2015, 4:21 am 
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I will get a snap of the access panel I had on the cobra I used to have, I think I could change both sets of pads on the inboard brakes before you could jack a car up and get one wheel off . Granted on a production car it's a pain without a ramp but not a problem if you planning a build and making allowances. I suppose we will all beg to differ on this heat issue , I do feel we are talking of extremes here though because I have been around this set up for many years now with road cars and kits ,I have never seen , witnessed or heard of this problem until it was mentioned on here. On the same token I will be using this set up on my tvr project and will take on board the possibilities of heat issues and build in ductwork as a safeguard.

Bob

Edit

F1 have used inboard brakes sucessfully for many years. It's only the increase in downforce which in turn lessens the impact of unsprung weight, larger wheels which means a bigger rotor and decrease in available space that made them go outboard. Some teams even found an advantage of going inboard on the fronts but increase weight with shafts etc stopped this practice. We could never give a car a bigger spanking than these guys.

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PostPosted: December 12, 2016, 1:13 am 
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There is one very serious limitation with inboard brakes at either end of the car.

With outboard brakes you can design a suspension geometry that produces some antidive at the front, and anti lift at the rear under braking. The callipers tend to drag the upright around the brake disc, which is where these "anti" forces come from.

You may have noticed that most Formula One cars very rarely use inboard brakes at the front, although it would be easy to do, and there is plenty of air.
And you may have also noticed that many drag race cars do not use an IRS, but prefer a live beam axle.
Anti dive and anti squat geometry is a very powerful tuning tool.

Jaguar that were among the first to almost universally use IRS on all of their vehicles for decades have now gone back to using outboard brakes at the back.

Maybe you do not need an "anti" suspension, you could just make the suspension rates rock hard.
But the reality is, softer springing and some "anti" (but not too much) is a much better overall compromise.

It may look high tech, and have lower unsprung weight, but getting the tires to stick and not running out of suspension travel is more important.


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PostPosted: December 12, 2016, 11:19 am 
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You can have anti-dive and anti-squat geometry without having torque applied to the outboard end of the arms (or the axle). Think about a parallel trailing arm four link at the rear as is typical on a seven - if your trailing arms are running uphill from the axle to the chassis, then you will have some anti-squat due due to the axle pushing forward on the arms rather than any torque effects.

You can do the same with independent suspension. If the inboard mounting points for your A-arms are not level front-to-rear you will end up with some anti or pro squat/dive. For example, on your front suspension you can have the front wishbone mounts (both upper and lower) a bit lower than the rears for some anti-dive, which doesn't require any torque on the outboard ends of the arms.


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PostPosted: December 15, 2016, 12:44 pm 
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My input since i am not seeing it anywhere... that break dust crap gets everywhere!!

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PostPosted: February 5, 2017, 4:22 pm 
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Bobber wrote:
Inboards pass all your braking forces through your half shafts, joints, etc.


Don't forget that braking forces ultimately appear at the tire contact patch, so everything that keeps the wheel positioned relative to the car is in the load path.

Re heating seals, that could be minimized with a 2-piece rotor with a spokey carrier.

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PostPosted: February 5, 2017, 8:01 pm 
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Inboard brakes - ask anyone who's changed pads etc. on the rear of an E-type Jaguar about them. Once the cursing finally peters out, you'll find out what they really think (I had to do this a couple of times...). :shock: :BH:

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PostPosted: February 5, 2017, 10:29 pm 
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I suspect whatever's gained by having them is offset by living with them. Very few cars have/had them and there's probably a reason why. Also, how many of us have the skills to monopolize the lower unsprung weight to justify the effort. Since I can answer only for myself, I couldn't justify them.

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PostPosted: February 5, 2017, 10:32 pm 
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This would depend on the type of caliper installed.

Some calipers you just pull 2 hair pins and slide out the retaining pins then the pads lift right out.
Other calipers have to be removed to change the pads.

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PostPosted: February 6, 2017, 12:35 am 
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That's true. Mind you, the Jag pads are easy enough to change....once you get to them. IIRC, the first step in changing the rear pads is to remove the seats, seatbelts, and carpets, so as to get to the rear end retaining bolts. Due to lack of access from below (it just wasn't possible), it was necessary to drop the entire rear suspension to get near the calipers & pads...not something for the home mechanic, unless you had a hoist.

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PostPosted: February 6, 2017, 3:26 pm 
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KB58 wrote:
Also, how many of us have the skills to monopolize the lower unsprung weight to justify the effort.


It doesn't take skill to appreciate a better ride and less skittishness on bumpy curves.

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