instruments Speedo cable rotation

[Rockie51]

I am fitting my new Racetorations gearbox tunnel to the TR4A. It has the removable cover that goes over the right angle speedo drive. My car came without the right angle drive when I bought it and I have had 2 speedo cables break because of the sharp angle that they come out of the gearbox onto the floor of the car.

 

I have bought a new right angle drive. I was looking at it yesterday and realised that it reverses the rotation of the cable. How is this going to affect my speedo? Did the cars with the right angle drive have a different speedo?

[Drewmotty]

The straight cable should come out under the floor not on top. Is this causing your problem?

[RogerH]

Hi Rockie,

it is normal for the 4A to have the right angle drive.

 

The cable must rotate in the correct direction with or without the RA drive.

 

Have another look at it. There have been no reports of the RA drive turning the wrong way.

 

Roger

[Rockie51]

Hi Roger

 

When I turn the input on the RA drive clockwise, the output turns anti-clockwise. Does any one have a spare lying around that they can check for me?

[Keith Lewin]

Hi Rockie51,

 

Just checked my brand new spare (yes, I carry one and can now change them quicker than a Williams pit stop), and it is as you say. Clockwise produces anti clock.

 

Not sure what speedo clock differences there may be as mine has always had the RA drive (several in fact) and I'm still a very raw novice.

 

Hope this helps,

Keith.

[Charlie D]

Rockie51,

 

Not sure if this makes sense, but...

 

The input to the right angle drive will actually be a mirror image of the output from the gearbox.

 

So you need to look at the “Input” in relation to the gearbox “Output”.

 

Clockwise from the gearbox = anticlockwise on the "Input" of the RA drive.

 

I’m not saying it very well, but I know what I mean.

 

Basically, I’m sure it’s OK.

 

Charlie.

[RogerH]

Hi Rockie,

 

The output of the gearbox is Clockwise

The output of the angle drive is clockwise

The output of the cable is clockwise

The output of the speedo is clockwise

 

All their inputs are counter clockwise.

 

'That nearly done my head in Brian'

 

Roger

[oldtuckunder]

But it does depend on which direction you are looking in!

 

I.e if you are stood in front of me rotating your finger in a clockwise direction, to me its rotating anti-clockwise

 

Only wishing to add more mud to the water!

 

Alan

[Lebro]

Hi Rockie,

 

The output of the gearbox is Clockwise

The output of the angle drive is clockwise

The output of the cable is clockwise

The output of the speedo is clockwise

 

All their inputs are counter clockwise.

 

'That nearly done my head in Brian'

 

Roger

How can the speedo have an output

 

Bob.

[Charlie D]

Bob,

You said:
"How can the speedo have an output ?"

That would be the needle !

However, I’ve just realized that Rockie51 is in Australia, which means everything is the other way round/upside down, so that may cause other problems.

Charlie

[RogerH]

But it does depend on which direction you are looking in!

 

I.e if you are stood in front of me rotating your finger in a clockwise direction, to me its rotating anti-clockwise

 

Only wishing to add more mud to the water!

 

Alan

 

Hi Alan,

quite so.

Which way do the hands of a clock move.

 

Clockwise when looking backwards (into the clock face)

AntiCW when looking forwards (into the back)

Up and down when looking from the side

Sideways when looking form above/below

 

It's like reading a book - why, in the western world, do we all read backwards.

 

Rohger

[Lebro]

Can't see the problem myself.

 

boB

Edited April 27, 2017 by Lebro

[AlanT]

This is all complete bollocks. The angle drive does NOT reverse the direction.

 

The problem is perceptual, in other words you have mis-observed what happens.

 

Just fit it. All will be well.

[BlueTR3A-5EKT]

This is all complete bollocks. The angle drive does NOT reverse the direction.

 

The problem is perceptual, in other words you have mis-observed what happens.

 

Just fit it. All will be well.

+1

 

I would also add that the use of a washer inside the attachment nut to space the angle drive away from the gearbox speedo outlet can be determined to be useful - notably as some repro angle drive input cables are too long casuing binding of the gears..... I have previously used a fibre washer that fitted diametrically perfect in the nut.

 

Peter W

[AlanT]

I always supply a machined Acetal washer about 3mm thick. There is plenty of thread in the captive nut.

 

These squash up and feel a bit like a Nyloc nut. KInd of smooth friction. You don't need to be extremely tight.

 

The neck of these drives, just below the captive nut, is quite thin and won't take a lot of abuse, like twisting.

[oldtuckunder]

 

Hi Alan,

quite so.

Which way do the hands of a clock move.

 

Clockwise when looking backwards (into the clock face)

 

 

Which of course raises the deep chronometry philosophical question

 

If you asked a clock which way its hands are rotating it would say anti-cloclockwise, which of course can't be true as it is a clock

 

Alan

[AlanT]

I can see I might have to make a video that shows this happening. Or rather NOT happening.

 

When I first set up a repaired drive, I nearly went mad trying to work out which way the gear-forces drove the pinion axially, in normal driving, so as to get the end-float control washers right.

 

It's amazing how bad the brain is at doing this kind of thing.

 

When I went for interview for University entrance, I was asked the following, I quote as exactly as I can:

 

" A astronaut is fired to the east. He circles the earth once, in 24-hours. He lands at the same place. How many sun rises did he see"

 

Pretty topical question in 1966.

Edited April 27, 2017 by AlanT

[Lebro]

2 ?

[AlanT]

Why?

[Lebro]

The earth rotates west to east ie anti clockwise when viewed from the north pole.

In 24 hours it completes one rotation, & so any given point say on the equator will see one sunrise.

The astronaut launches east, so is going the same way as the earth, he travels around the earth, and gets back to where he started after 24 hrs.

to do this he must be spinning at twice the speed of the earth, & so in 24 hrs he will see 2 sunrises.

 

( or she of course)

 

Bob.

[AlanT]

You are better at this than me.

[Rockie51]

I love this forum. I ask a simple question about a speedo cable and it turns into a deep philosophical discussion.

[AlanT]

Too many academics on here for anything else to happen.

[Charlie D]

Alan T,

I’m intrigued by the question you were asked:

" A astronaut is fired to the east. He circles the earth once, in 24-hours. He lands at the same place. How many sun rises did he see"

I would say:

“He/she would not see a single sunrise.”

The examiners would no doubt laugh at me.

I would then explain:

“The reason being that to be fired into space at such a speed that they circle the earth once in 24 hours would result in such high G-forces that he/she would have temporary blindness for 48 hours, and therefore could not see anything.”

What I was taught at school was:
“The Rule of 3 Bs”.
(Bulshit Baffles Brains.)


Charlie.

[AlanT]

Actually a low earth-orbit means an orbit period of an hour or so. Check the GPS satellites.

 

To orbit once in 24 hours means you go a long way out. I was bothered about this at the time. Maybe he could see the sun the whole time?

 

The geostationary satellites, which go at earth speed, are at 30000 km. Think they are always in sunlight.