Lotus Elan

driveshaft handbrake

PostPost by: h20hamelan » Wed Apr 25, 2012 5:00 am

some 4x4ers use a inline driveshaft handbrake, it locks the driveshaft from turning and thus the wheels
a basic disc drive shaft handbrake would be too large in some areas, what about near the transmission or half-shafts

any thoughts

thanks
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PostPost by: reb53 » Wed Apr 25, 2012 7:05 am

I suppose moving the calipers inboard would remove some unsprung weight but there could be a problem, ( apart from the fact that the design was signed off 50 years ago, and we're not all about to retrofit our cars....)

With the Elan's rotoflexes how far would the car move if you put the handbrake on whilst on an incline ?
I have a vague recollection that this was tried ?

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PostPost by: ardee_selby » Wed Apr 25, 2012 8:01 am

reb53 wrote: With the Elan's rotoflexes how far would the car move if you put the handbrake on whilst on an incline ? I have a vague recollection that this was tried ?

Cheers
Ralph.


Ralph,

It got a mention on here a looooong time ago:

post25618.html?hilit= inboard#p25618

Cheers - Richard (and they said I wouldn't last :wink: )
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PostPost by: SADLOTUS » Wed Apr 25, 2012 9:15 am

Hi, I'm not sure h20hamelan was meaning the repositioning of the existing calipers/handbrake - (were you?) I think he was asking if a separate handbrake mechanism could be constructed using a small motorcycle/bicycle caliper -hydraulic or cable- adjasent to the prop which would have a small disc mounted on the probshaft and operated by the existing lever or a new lever. The likely area in my opinion would be between the prop and the diff. I've thought about this for years and while my car still scrapes through the MOT and seems to be running fine (mmm... shouldn't have said that) it's a back burner thought.

Actually, I'm surprised Spyder haven't come up with something like this - just an extra lug on their chassis.

http://www.streetrod.com.au/brakekits.htm

http://www.jdmgarageuk.com/ksport-hydraulic-handbrake
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PostPost by: oillite » Wed Apr 25, 2012 11:26 am

Given the tight for space nature of the elan chassis if done it would be hard to keep serviced.
I my experience of transmission parking brakes on big lorries* like Fiat's and lighter lorries like Bedford's they were a pain in the back side.

Trucks*
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PostPost by: h20hamelan » Wed Apr 25, 2012 3:38 pm

Hello

Thanks Yea something that is easier to fix maintain etc

I am newer to the elan, and have been thinking there may be/ should be/ could be something else

but yes, the traditional 4xers' use a large diameter disk.

something to lock the wheels easily, a disk behind the trans mating to output-shaft???

kind regards
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PostPost by: Chancer » Wed Apr 25, 2012 3:52 pm

I had a shogun with a transmission brake, it meant that unless the water came up to the drivers waist it would usually keep dry, the other advantage was a mechanical advantage equal to the diff ratio, it pulled up really hard.

My party trick was to yank it on when the vehicle was within say 12" of coming to a stop, it would bounce very violently backwards and forwards enough to make some people lose their breakfast, the addition of rubber donuts in the drivetrain especially the modern chocolate teapot type doesnt bear thinking about :shock:
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PostPost by: h20hamelan » Wed Apr 25, 2012 8:28 pm

shogun sounds fun
and a bit of work

this from a link.....................
As an electrical engineer with 30+ years of experience and WAY too much time on my hands, I'll add my 2000 cents.

The concept behind the device is fairly reasonable, although the execution and price might not be.

A solenoid is nothing more than a hollow electromagnet with a movable element in its axis. When a solenoid is energized there is a strong magnetic field created which is especially concentrated in the hollow center. It is this magnetic force that moves the hydraulic valve controlling the trans-brake. When the solenoid is de-activated the magnetic field collapses on the windings which created the field to begin with. A changing magnetic flux induces a current in any electrical conductor which crosses the magnetic field lines as discovered by Faraday in 1831. This is the exact same phenomenon that is at work in an ignition coil (which is actually a transformer which has two electrical windings as opposed to the one in a solenoid). So the collapsing magnetic field induces a current in the solenoid windings even though the trans-brake switch is open.

If a current is induced in an electrical circuit, then it has to flow, regardless of how much resistance there is to that flow. Ohms law says that voltage = current times resistance (V=I*R). Since the trans-brake switch is open, it's resistance is essentially infinite (but not really) and the current is greater than zero, so that means that the voltage also has to rise toward infinity. Of course the voltage won't reach infinity since something in the circuit is going to be unable to withstand the rising voltage and will electrically break down, allowing the induced current to flow. In an ignition system, what gives is the resistance across the spark plug gap when the fuel/air mixture ionizes causing the current to flow very radidly in the form of a spark (unless you have a "bad" plug wire and it breaks down first, causing a miss in that cylinder).

The trans-brake circuit is part of the car's normally 12 volt electrical system. Since it is a low voltage system, there is usually something in the circuit which cannot withstand the voltage rising beyond 60 volts or so and whatever that something is will break down and conduct, allowing the induced current to flow.

Automotive electrical systems are some of the nastiest systems that engineers have ever had to deal with. There are all sorts of faults which must be tolerated, such as alternator load dumps, reversed batteries and horrendous EMI from the ignition system. Any properly design automotive electrical (and especially electronic) device will have circuitry whose purpose is to protect the device from excessive voltage. In almost every case, this protection circuitry will begin to conduct when the 12V input rises above a safe level for the device. It is this (these) path(s) where the current induced by the solenoid finds it's way to ground.

So, the graph shown in an earlier post is accurate in that it illustrates the voltage spike on the +12V circuit which can occur when a sufficiently large energized solenoid is de-energized.

So what? The fact of the matter is that the spike in voltage occurs AFTER the solenoid is de-energized, i.e., AFTER the trans-brake is released. The voltage spike is not going to re-energize the solenoid since the voltage is going the wrong direction for that to happen. The spike MIGHT affect other electrical (or electronic) devices that are on the 12V circuit, such as a delay box or ignition box, but these devices should have their own over-voltage protection. If they are properly designed they won't give a hoot about the voltage spike. If they ARE affected then THEY should find their way into the lake at E-town since they are not up to the task of operating in the inevitably nasty electrical system of a racecar.

So what is inside this "stop it" thingy? One post said it was a resistor and capacitor in parallel, then later said it was a resistor and a "diode so that the voltage wouldn't feed back". I have not been inside one of these things so I'm only speculating, but from an engineering perspective it makes no sense at all to have any capacitors in that box. A capacitor and resistor combination would cause an electrical delay which would likely vary with temperature and do nothing much to suppress the voltage spike, although it could spread it out over time depending on the values of the resistor and capacitor. An RC circuit would also act differently with different solenoids since their inductances are not all the same. More likely there is a low ohm resistor and a semiconductor known as a "transzorb" or "varistor" in series which makes the most sense electrically.

A "transzorb", a.k.a. "transient voltage suppressor" is a semiconductor which is specifically designed to limit the transient (i.e. short-term) voltage on an electrical circuit such as an 12V automotive supply. Physically it looks like a diode and electrically it sort of operates like a specific type of diode known as a "zener diode", but it is not the same thing. A transzorb reacts very quickly to voltages that exceed a particular level and is designed to absorb large amounts of power for very short periods of time, which is exactly the situation created when a large solenoid is de-energized. It's function is to "clamp" the power rail at a set voltage level (usually 18 to 20 volts for automotive use) and absorb any excess transient power that is on the rail. Putting a low value resistor in series with the transzorb would make sense to limit the current through the transzorb under extreme conditions.

So, my guess is that it what is in the box. If you have quality electronics on your car, they will be designed to withstand any voltage transients (probably with transzorbs of their own). You can buy a transzorb and resistor that would do the same thing as the box for less than a dollar, it just wouldn't be as pretty.


....................................


is it easier to find room for a disk somewhere?????????????????

thanks
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PostPost by: JJDraper » Thu Apr 26, 2012 6:17 am

Easier to get the handbrake working properly.

Off topic I know, but I had my rear calipers refurbed by a well known Cheshire outfit some eight years ago and they have worked well ever since. BUT, the mechanism does need regular cleaning - at least once a year, and more frequently if you don't use the car much. I uncouple the link, pull out the pads and give the whole lot a brush down and wash with WD40 or similar. The clamps often get a bit tight on the pivots so the lube needs to be worked in to get them moving freely. I finish up with some spray on water resistant grease, and put it all back together. Takes about an hour for both sides. Adjust to bite in the first two clicks of the handle. Pads last about three years - 20-25k miles. I admit that I do adjust it closer than normal for the MOT test, but it works well in traffic and will hold on substantial inclines. Prior to refurb, they were hopeless...

re electronic driveshaft brake - how about a KERS system?!

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PostPost by: Galwaylotus » Thu Apr 26, 2012 8:05 pm

Wheel ckocks - yer only man! :twisted: :lol:
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