Angle Drive Gear Reduction Ratio?

[Nicholas R]

Thanks for this info!! Definitely all makes sense now (all except why the Hervey ones are 1:1).

I suppose that since the rate of rotation is liner compared to the position of the needle about the center of the gauge, if you bought a Hervey one, you could simply remove your needle and reposition it the amount that it is off.

[Bitsyncmaster]

Thanks for this info!! Definitely all makes sense now (all except why the Hervey ones are 1:1).

I suppose that since the rate of rotation is liner compared to the position of the needle about the center of the gauge, if you bought a Hervey one, you could simply remove your needle and reposition it the amount that it is off.

That may work for MPH but your mileage counter would stay off 12.5%.

[Nicholas R]

That may work for MPH but your mileage counter would stay off 12.5%.

That is indeed a very good point; I had not thought of that.

[Shep]

To be honest, I'm kind of surprised no one's gone after Hervey legally for using the wrong ratio. There's quite a few D's out there whose mileage is seriously understated. 12.5% may not seem like much, but on a 200,000 mile car, that's 225,000 miles -- quite different considering the number of high-mileage DeLoreans out there! Some of us have managed to keep accurate mileage on our titles, and that kind of difference not being disclosed leaves a seller vulnerable to legal recourse from the buyer. It's essentially a form of active odometer rollback, which is not good all things considered. Food for thought I suppose.

[Mark D]

Man that's surprising and kinda not surprising at the same time that Hervey's angle drives have been wrong all these years.

[LordFly]

And here's a picture of both. Notice the wear on the teeth. Oh, BTW, to all those who still believe that the gears are made of plastic - they are made of metal but this setup is made to destroy itself. The forces are huge and whoever designed this setup with the angle drive and two cables with two counters was a complete idiot.
Attachment 30927

Awesome, thanks! Well, I'm no certified engineer or anything, but why wouldn't they have used a bevel gear? The forces on a helical setup like that look like they'd be really bad!

I suppose that since the rate of rotation is liner compared to the position of the needle about the center of the gauge, if you bought a Hervey one, you could simply remove your needle and reposition it the amount that it is off.

No, that won't work, it's a ratio. If it's off 12.5%, at 100mph it's off by 12.5mph, but at 10mph, it's off by 1.25mph. Moving the needle won't work. Unless of course you only ever drive one speed.....

[DMCVegas]

To be honest, I'm kind of surprised no one's gone after Hervey legally for using the wrong ratio.

What could you possibly get him on? Most cars are exempt from milage once they hit 10 years anyhow, and if wrong ratios opened a person up for a lawsuit, I'm sure that tire shops would only sell OEM sizes or combinations thereof.

Even if you had a car that actually made it 100,000 miles and you got shorted on the milage, how would you prove a loss on the depreciation? Just something to think about.

[Shep]

What could you possibly get him on? Most cars are exempt from milage once they hit 10 years anyhow, and if wrong ratios opened a person up for a lawsuit, I'm sure that tire shops would only sell OEM sizes or combinations thereof.

Even if you had a car that actually made it 100,000 miles and you got shorted on the milage, how would you prove a loss on the depreciation? Just something to think about.

True, hadn't considered that aspect of it.

[LordFly]

For what it's worth, I'm honestly not sure how durable the plastic gears would be, particularly if you're going for extruded plastic

Oh I totally don't expect them to hold up. But then again, my angle drive lasted 9km the last time I hooked it up. Mostly I'm just curious if I can make something that fits and kinda works. A way to test my skills in SolidWorks

[Tomcio]

Awesome, thanks! Well, I'm no certified engineer or anything, but why wouldn't they have used a bevel gear? The forces on a helical setup like that look like they'd be really bad!

Even if you're not an engineer your thinking is much better than that of the engineer who designed this setup. Bevel gears would be a much better choice in this case as the forces are now just huge. Bevel gears with angled teeth would be quiet and would last the life of the car. No wonder those angle drives keep failing.

What could you possibly get him on? Most cars are exempt from milage once they hit 10 years anyhow, and if wrong ratios opened a person up for a lawsuit, I'm sure that tire shops would only sell OEM sizes or combinations thereof..

Well, I can think of one possibility here and that is speed. If the speed limit is say 75 MPH and your needle is exactly at 75 then your actual speed would be 75 + 12.5% = 84.375 MPH and that could get you a nice ticket. I would definitely like the person responsible for my ticket to pay up.

When it comes to tires there is a limit of how far they can go with different sizes before they have to tell you that your speedometer will be off. The new tire size should be within + or - 3% of the original size. In case of the angle drive we're talking about 12.5% difference and the customer apparently isn't informed about this.

Oh I totally don't expect them to hold up. But then again, my angle drive lasted 9km the last time I hooked it up. Mostly I'm just curious if I can make something that fits and kinda works. A way to test my skills in SolidWorks

I don't think plastic gears from a 3D printer would last more than 9 turns let alone kilometers. The forces are really great in this setup even without the cables and two counters. Try building one using bevel gears with the same ratio and they might last for a few kms. Or better yet go back to your original idea of a complex transmission that provides the same ratio. That might actually work... if you use a planetary gear set the forces would be divided among all those teeth working together. That's a cool idea