How to Find Out What Gears Are in My Truck UPDATED

How to Find Out What Gears Are in My Truck

I tin remember information technology conspicuously; my older brother got a Lego Technics set for his altogether and I saw gears for the offset time! I wanted to play with them so desperately that I stole a few when he wasn't looking. I got caught.

Lego has simplfied the gear option procedure greatly so when you desire to use your own real world system, it is a bit more complex and there are a lot of choices to make.

Gears transmit power between shafts and the ii main purposes are to modify speed and direction. In order to utilize gears properly, matching diametric pitch and force per unit area angles must exist used. Lubrication and proper backlash adjustment are important to ensure long life.

Let's take a look into the seven questions that demand to be answered to properly employ gears.

1. What blazon of gears practice I need?
2. How will it mount on a shaft?
3. What is a pressure angle and which one exercise I want?
4. How exercise I cull the diametric pitch?
5. How practice I summate gear speeds and forces?
6. How do I lubricate my gears?
7. How practice I make sure my gears aren't too sloppy?

Gears vs Sprockets

And so, the offset affair I desire to mention is gears are not sprockets and sprockets are not gears.  Gears are meshed with other gears.  When a standard set of gears are meshed, they will turn in opposite directions.  Sprockets on the other mitt are connected by roller chains and will plough in the same direction.  Sprockets go with chains and gears mesh with each other.  The images beneath show how the tooth profiles are different equally well.

What type of gears do I need?

Epitome courtesy of Flickr

Spur gears

Spur gears are the most mutual type of gear.  They are easy to produce and widely available in a multitude of materials.  For those of you familiar with Legos their most mutual gears are spur gears in eight tooth, a sixteen tooth, a 20-4 tooth, and xl tooth.

They all volition work together with each other because they all accept the aforementioned diametrical pitch and pressure level angle which allows the gears to mesh with each other (more on that later on).   All gears have the same diametrical pitch and pressure angle in the Lego universe.

Small gears are sometimes called pinion gears or just pinions.  They usually refer to a gear that drives a larger gear.

The biggest indicator of a spur gear is the molar is completely parallel with the shaft axis.  These have the best efficiency of all gear types since meshing gears won't create side forces.  They as well have a 'line contact' indicating that the unabridged face of the gear should exist contacting the other gear.  A downside is that since the gears are always contacting and releasing each other, they tend to exist noisy at college speeds.

Rack gears

Rack gears are a version of a spur gear that has substantially been cut and flattened out and it has the aforementioned diametrical pitch equally a round gear, except rack gears don't have bore, and then they've kind of fudged that a niggling bit and they just continue the same diametrical pitch.  If that confuses you, think that it is only a section of a gear with an infinite radius.

If you've ever heard of rack and pinion steering, it is describing a rack gear being moved side to side by a pinion gear.  In the moving picture below, we have modeled the front end of a car and you can come across the pocket-size pinion gear and the rack attached to the steering artillery.  The artillery are attached to the front axles.  When I plow the steering wheel, the pinion turns and shifts the rack from side to side.  Pretty elementary.

Worm Gears

Another gear type is a worm gear where the teeth are wrapped around the axis of the shaft.  It meshes with a more standard gear at a ninety-degree angle.  This more standard gear normally has a slight bending to match the advancement of the work.  More often than not, the larger gear is the driven gear and the worm gear is the driving gear.  As we plow the worm gear, we only become i tooth advocacy for one revolution on the input.  At present depending on how you design this you can get cracking interface betwixt the two gears so that you're non only wearing on ane tooth.  You can see that many teeth on either end of the worm gear don't get any wear.

Worm gears are mostly self-locking at about a 15:1 ratio but that is also dependent of gear lubrication and friction in the bearings.

Worm gears don't take to be single indexing arrangement; meaning that in that location is only one set up of teeth going around it.  Other possibilities are double or even triple indexing threads.  When I was in high school, I got to tour the Statue of Liberty.  Inside the statue, there is a double helical stairway.  This stairway immune a path for people going upward and one for people going downward.  (It was really steep as well.)  This is the aforementioned for a double indexing worm gear, I went around once, simply actually avant-garde 2 staircases high.

Worm gears are well-nigh prevalent in winch applications where y'all don't want the spur to motion unless driven.  Y'all tin can also better braking, by calculation a restriction.  The brake is usually removed when hydraulic force per unit area is applied.  Another application would exist crane rotation.

So, the spur gear that interfaces with the worm gears actually has different in profile.  If I turn the gear then that the axis is 90° to me, the teeth won't exist flat.  They will have a slight scallop to them to lucifer the worm gear.  This gives better contact surface area which decreases wearable.

Mitered or Beveled Gears

Mitered and Askew gears have the teeth cutting on well-nigh a 45-caste angle to the axis of the shaft, and that's so that you lot can interface with 2 of them and class a xc-degree bending.  Now you can change the direction from being in the same axis to them existence ninety degrees apart.

There is a departure between beveled and mitered gears.  Beveled gears are shaped differently that mitered gears making them a improve selection in the transmission of movement and not power.  As a result, they work well with unlike gears with differing number of teeth.  They are too quieter because the contact is inverse from a line contact to a 'signal contact.'

Miter gears on the other hand are intended to simply mesh with gears of the same number of teeth and that leads to a line contact situation again.  Every bit a issue, efficiency increases.

Cog Gears

Cog gears have all simply disappeared from the industrial world.  It is mostly a slang term now for gear.  Back in medieval times, it was very difficult to shape a gear molar, so they used a mostly foursquare molar and slot blueprint.  This was great at transmitting motion, but very inefficient for transmitting torque.  These have pretty have been totally replaced past a spur gear.  The movie here shows the Lego version of the cog gear.  The tooth blueprint on it is very crude, but Lego keeps the design because at that place are a number of ways to transmit move with it.  Even so, because of the large cuts between teeth, it is not recommended for ability transmission.

Helical Gears

The major downside to spur gears is that when you get upward to high speeds, they start making noises when they interface with each other.  If you have a manual transmission auto, yous may accept noticed when yous are in reverse there'due south a whine.  That happens considering the reverse position activates a set up of spur gears.  So why are the other gears in my transmission and so quiet?  The reply is they use helical gears.

A helical gear is like a spur gear, but the tooth is cut on an angle that somewhat wraps around the gear.  The lack of racket is caused by the line contact of a spur gear being replaced by a point contact.  Equally the gears mesh, there is ever a shifting in contact beyond the confront of the gear tooth.  Because the teeth are wrapped around the gear, multiple teeth will be meshing at the aforementioned time but at different places across the face of the gear.

How will it mount on a shaft?

The short answer is keyed shafts.  By far any off the shelf gear with exist available in a variety of bores sized with keys slots.  You can as well buy them with unfinished bores and either cut your ain keyway or cutting an anfractuous spline.

When selecting a bore size, make sure that you lot aren't selecting a shaft that is also big for the for the gear.  Recently, I had a system that used a 10-tooth sprocket on a 1" shaft.  The system had some pressure level spikes in it at startup and really cracked the sprocket in half.  It was able to practice this and so hands because the material betwixt the exterior of the hub and the keyway was merely ane/eight" thick.  Nosotros were able to double that to ¼ past adding one molar.

Most gears are held in with just i or two set screws.  Mostly, one screw will be on the central and the other will be xc° to information technology and printing against the shaft.  For spur gears, this is adequate, merely for helical gears, there needs to be more of a positive engagement on the shaft to account for the side load.  Possible solutions are thrust bearings, tapered roller bearings or snap rings.

Read this commodity for more information on this subject area.

What is a pressure angle and which one do I want?

There is a lot that goes into the design of a gear tooth.  Now I don't know all the specifics of tooth design and more importantly, I don't want to burden you with them either.  But somebody has thought this out, done a lot of careful planning and lot of calculation on tooth design.  Permit's leave this subject to the experts and build off their theory, knowing that it works.

Gear teeth are designed with the unique profile and it's called an anfractuous profile.  The anfractuous contour is made by taking a cord and wrapping it effectually a cylinder.  We then trace the curve as it unwinds.  Every bit you can see, a bend with a constantly increasing radius is made.  This is very similar to the Fibonacci bend sometimes known as the Gold Spiral.

The section of the anfractuous curve we use is determined by how close or far away from the center cylinder and how large the cylinder is to begin with.  Again, let's go out that to the experts and just keep their theory and know that it works.

A pressure angle is defined as the instantaneous angle the anfractuous has where it intersects the pitch circumvolve relative to the molar.  But that'south not of import for what we want to do, so forget that. Here is what is important:  Pressure angles for meshing gears must lucifer.  Standard pressure angles are 14.5° and 20°.  To a lesser extent 25° is also bachelor.  The higher the pressure angle, the effectively the teeth.  If we're interested in power transmission, use the xiv.v° blueprint.  The 20° angled gears are more for precision because they have very little backfire.  However, the you will demand to hold the center to center distance much tighter.

How do I choose the diametric pitch?

Unfortunately, we do demand to take a piddling bated to specify some terms here.  I promise, it volition exist cursory.

Lands – They are the "flattened" department of the tooth.  The top land is the state at the maximum extent of the gear and the bottom country is at the minimum diameter.  When meshed, there should exist a pocket-sized gap between the lands.

Pitch Circle – The pitch circle is the constructive diameter of the gear.  Ideally you will desire the pitch circles of two gears to be tangent to have the correct distance between them for meshing.  This information is usually given by the manufacturer and is normally referred to as the variable "d".

Diametrical Pitch – Diametrical pitch is represented by PD and has units of teeth/in (TPI).  It is the number of teeth on the gear divided past the pitch circle (d) of the tooth.  This information is supplied by the manufacturer. The diametrical pitch must be the aforementioned for gears to mesh.  Since I like Legos, we volition use them to exercise a little example.  Lego block have the holes 0.314" apart so we will use that as our measurement.  If I mesh two of the viii tooth gears, we can see that the pitch diameter is one pigsty or 0.314.  Our PD is 25.v TPI.  The 16-tooth gear uses 2 holes or 0.628" and Our PD is 16 / 0.628 or 25.5 TPI.   We would also find that the 24 and 40 tooth take a 25.5 TPI if nosotros did the math. These gears mesh together because they take the same pressure level angle and diametrical pitch.

How do I summate gear speeds and forces?

Gear Speed Ratio

With gears, the speed ratios are quite simple: you count the teeth.  Assuming that the gears have the same diametrical pitch and pressure bending, they will mate.  Now all we have to practice is count the teeth to see what the speed ratio will be.  If we use a 40 tooth and viii tooth gear, we tin can divide by the smaller one and come across that our ratio is 5:ane.  That is the smaller gear will demand to rotate five times to cause the larger gear to rotate once.  The gear ratio will tell u.s.a. how speed and torque are related.

For case, we have a ane hp electric motor rotating at 1800 rpm and the shaft is attached to the 10-tooth gear and drives a 45-tooth gear.   We can summate that the gear ratio is 4.5:one.  From this, nosotros can calculate the output speed is 400 rpm.  The input torque at 1800 rpm is about 35 in-lb.  We can then multiply this past our gear ratio and find out that the maximum output torque is 175 in-lb.  It needs to be noted that this does not account for whatsoever inefficiencies in the organisation.  Gear mesh inefficiencies and bearing friction will reduce the torque transmitted but have no event on the speed.

Spur Gear Forces

Now we are going to talk nigh the manual of torque and force. The first thing nosotros're going to do is create a quick complimentary body diagram on a gear tooth.  Because of the involute tooth pattern, we can brand our calculations based on contact at the pitch circle diameter.  Nosotros accept the tangential force, F_t which is the input forcefulness that transmits movement.  Because of the gear'due south pressure angle, we now have a radial force, F_r, that pushes the gears apart.  As you tin see, having a higher pressure angle will create higher radial forces.  To maximize efficiency, ball or roller bearings are oftentimes used fifty-fifty when rotation speeds may be boring enough to employ cylindrical or other non-moving bearings.

By solving for the statics, nosotros can observe Fr and the total forcefulness F.  The total force is almost a useless number, but it does give some indication of how efficient the system is.  The higher the ratio of F_t/F is, the more efficient the teeth are.  Standing our example, we find that the forces on the gears are as follows:

Helical Gear Forces

Helical gears have an added level of complication non only in design, simply also calculation.    In the gear higher up nosotros still take a 14.5° pressure level angle, but the teeth are cutting at a 18.93° angle from the shaft axis, represented by ψ.  From the diagram below, we slice the gear two ways with θ_t equal to the gears force per unit area angle and θ_n which the pressure angle when viewed from the terminate of the gear. Now we tin offset calculating our gear forces.

Since the gear tooth is cutting at an bending to the rotation axis, it should exist no surprise that we are now going to take an centric component in our calculation.  As a effect, you lot will demand to think of how you lot want to deal with this load.  Having a set up screw taking this load might be adequate if you are using small torques, but y'all will probably demand to upgrade to tapered roller bearings or thrust washers if your loads are high.  Apparently, having the axial component will decrease our overall efficiency of the system as our ratio of tangential forcefulness to full force dropped from 97% to 92%.  One thing to note nearly changing from our spur gear is that the radial force remains the same.

Tooth Forces or How a Gear is Actually Sized

So, it all comes down to the force and stress exerted on the molar.  For every bit complicated equally the gear molar profile is and all the points that the gear can contact at is the formula is surprisingly simple.  Recall those actually smart guys that came up with the involute profile I was telling y'all nearly before.  This is where they actually earned their money.

Where F_t is the tangential forcefulness, σ_a is the allowable stress, due west is the effective width of the gear, Y is the Lewis form factor and PD is the diametric pitch.  As always, sentry your units.  For this, you can stay in pounds and inches.

Lewis Course Factor

The Lewis Form Gene is the real genius of the performance.  This factor takes in all the geometric variances with the involute profile and puts them in a nifty picayune table shown here.  Y'all can encounter that increasing the number of teeth increases the factor as well as going to a college pressure level angle.

If you want to increase your molar adequacy, you lot tin can increase your allowable stress, gear width, or use larger or college pressure angle gears.  You tin also subtract the diametric pitch, because fewer teeth per inch ways larger (and stronger) teeth.

Barth Speed Factor

The equation for finding the commanded stress is for static gear meshing or those running at very depression speeds.  Unfortunately, we probably want our gear systems to run at some speed and so nosotros demand to add in a factor to account for speed.

Adding the Barth Speed Gene, k_d, decreases the commanded tangential forcefulness.  The gear speed is the velocity of the teeth at the pitch diameter measured in ft/min.  The constant a is based on the gear design and is 600 ft/min for regular gears and 1200 ft/min for precision gears.

With these equations, you should almost be able to calculate the tangential forcefulness.  We are merely missing what the allowable stress is.  Unfortunately, I cannot give an like shooting fish in a barrel answer.  I can only give the lawyer answer: It depends.  Hither are some of the factors that volition play a role in computing the commanded stress

• Hertzian contact stress
• Gear ratio
• Material
• Surface roughness
• Lubrication
• Overload
• Dynamic Load
• Temperature

Each of these factors tin be very hard to determine.  I wish I could be of more than aid, but every case is dissimilar.  My advice to you lot is this, go conservative! Summate the maximum load that system can see and use a blueprint factor or 3:i on yield stress. Brand sure that your gears are well lubricated as well.  Designing to these criteria will put y'all on the side of caution.  Remember nobody complains if your gear system lasts forever.

How do I lubricate my gears?

There are primarily 3 methods of gear lubrication:

1. Grease
2. Splash
3. Forced oil circulation

Permit's examine each in brief

Grease lubrication

Grease lubrication works best with open geared systems.  You lot basically spray on lubricant that sticks to surfaces.  Since it is spray on, it has 2 major downfalls.  First, it will have to be reapplied often.  Second, since it is sticky, it is like grease and volition attract clay.  As you can imagine getting some "sand in your gears" is not a practiced thing.  Grease lubrication is meant for slow moving gear systems less than fifteen ft/s tangential velocity.

Splash lubrication

Splash lubrication is where part of ane or more than of the gears are in an oil bath.  Every bit the gears plough, the lubricant volition stick to the surface and lubricate the other gears in the system. I recommend this way of lubrication because all of the connecting gears go lubricated. As well, because the lubricant is thin, there is less ability loss between gears.

Forced oil apportionment lubrication

This involves oil or other lubricant to be pumped and put directly on the gears.  The delivery can be poured, sprayed or fifty-fifty misted.  This is used primarily when y'all accept open gearing simply working inside a building or fifty-fifty a very big gearbox.  One benefit is you lot are also able to control the oil temperature and cleanliness.

I accept used this method in the past where it was impossible to lubricate all the gears from the aforementioned pan. The application used a multitiered oil pan where lubricant was pumped to the highest pan and would spill over to the next pan when information technology was too high.

How do I make sure my gears aren't too sloppy?

Sloppiness in gears is called backlash.  In gear design, at that place is a gap between the lands; but there should also be a gap on the side reverse side of contact.  If that gap is too much, there is sloppiness.  If information technology is too piffling, there gears will article of clothing prematurely considering of interference.

At present imagine we are looking at a crane's rotation bearing.   When we rotate the crane boom, nosotros don't desire the begetting to repeated wiggle side to side when the crane stops.  Mostly, if the backlash is too loose, the crane with jerk back and forth until friction finally stops rotation.  That repetitive jerk on the gear teeth volition cause teeth to break off from fatigue.   To minimize or fifty-fifty eliminate this, you want to go those teeth very tight to each other.  You lot can do this by moving one of the gears closer to the other by changing the middle to centre distance.

My favorite way to conform these is to accept one of them, usually the pinion, and make an eccentric ring as shown.  The eccentric ring has an outer diameter that is off middle from the inner diameter.  Commonly, one/xvi" of an inch would exist more than enough.  The ring would sit in a bore and could be rotated as needed to adjust the shaft closer to or further apart from the other gear.  Once you have it properly adapted, y'all will demand to lock information technology in identify.  I have a few ideas here, only I volition not share them because they are proprietary.  You will desire to use anti-seize so that you tin get these components apart someday.

Measuring Backfire

Backlash tin be measured quite hands by using a magnetic mounted punch indicator.  Hither are the steps to gear up backlash:

1. Observe the high side of the teeth if possible.  If the bearing is new there is usually a mark from the vendor.  Rotate so that the pinion is acting on those teeth.  (Side note: you lot as well want the high side of the teeth to be meshed when the unit is stowed.  For mobile equipment this limits the bear upon from route vibrations.)
2. Generally speaking, the pinion gear will exist much smaller, so we will want to mountain the indicator on whatever moves with the pinion.  In the case of a crane, it is probably the turntable
3. Adjust the indicator so that signal is touching a tooth on the stationary side as close to tangential as possible.
4. Wiggle the moving part (i.e. turntable) past pushing and pulling on information technology from side to side.  Watch the indicator and annotation the range of motion.
5. Adjust the eccentric ring or other device until the range of motility is as desired.  This is normally around 0.005" to 0.010" (0.12 to .25 mm).
6. Lock the eccentric band in place.

Conclusion

Gear systems are everywhere and fun to design and use.  This commodity is designed to go the gear novice at least speaking the language of gears and hopefully equipped to design a organization of their ain.

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How to Find Out What Gears Are in My Truck UPDATED

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