THE CRASH GEAR BOX

[quote=mick88;1812268]

Quote:

---

even the girls were able to understand this. Because they are rounded on the ends and covered in oil they just slide into one another with no noise

---

So how did this get past the censor/moderator ?;)
Bill.

What about dog gears/clutch's????

Quote:

---

Originally Posted by wagoo

In addition to the types mentioned there are also constant mesh spur gear boxes. These are sometimes referred to by Rick130 and other racing types as 'dog boxes' These are a little different, slightly quieter and more pleasant than the dog box my dear wife used to occasionally order me to spend the evening in.:(
Bill.

---

These are the second type I mentioned in Post#4. They have spur gears rather than helical gears for a bit more strength. They are far noisier and thus acceptable for competition vehicles but not passenger vehicles. Shifting is accomplished in the same way, by moving sliding dog clutches a la Road Ranger.

By the ay, in speedway a "dog box" is the device used to connect and disconnect the crankshaft to the tailshaft. Midgets and sprint cars do not have a flywheel, clutch or gearbox.

Quote:

---

Originally Posted by Brian Hjelm

These are the second type I mentioned in Post#4. They have spur gears rather than helical gears for a bit more strength. They are far noisier and thus acceptable for competition vehicles but not passenger vehicles. Shifting is accomplished in the same way, by moving sliding dog clutches a la Road Ranger.

By the ay, in speedway a "dog box" is the device used to connect and disconnect the crankshaft to the tailshaft. Midgets and sprint cars do not have a flywheel, clutch or gearbox.

---

There doesn't appear to be universal agreement among engineers that spur gears are actually stronger than helicals. Some point to the fact that for a given width, the longer tooth of helicals are actually stronger, whilst others site that when a helical gear fails, often the teeth aren't broken over their whole length, which points to axial tooth loading that spur gears are generally not subject to. The high end thrust loads, plus the extra heat that helical gears generate can cause issues with bearings, thrust washers, circlips etc, and may be a factor in why spur gears are favoured for competition and heavy duty commercial transmissions such as Road Rangers. To compensate for any possible strength issues without the need to greatly increase gear sizes, Road Rangers etc have twin countershafts (layshafts) to spread the loadings over twice as many gear teeth, similar to how a 4 pinion diff(Maxidrive etc) is much stronger than a 2 pinion one(standard Rover type).
Bill.

Quote:

---

Originally Posted by wagoo

There doesn't appear to be universal agreement among engineers that spur gears are actually stronger than helicals. Some point to the fact that for a given width, the longer tooth of helicals are actually stronger, whilst others site that when a helical gear fails, often the teeth aren't broken over their whole length, which points to axial tooth loading that spur gears are generally not subject to. The high end thrust loads, plus the extra heat that helical gears generate can cause issues with bearings, thrust washers, circlips etc, and may be a factor in why spur gears are favoured for competition and heavy duty commercial transmissions such as Road Rangers. To compensate for any possible strength issues without the need to greatly increase gear sizes, Road Rangers etc have twin countershafts (layshafts) to spread the loadings over twice as many gear teeth, similar to how a 4 pinion diff(Maxidrive etc) is much stronger than a 2 pinion one(standard Rover type).
Bill.

---

Yes, I know all this. I served an apprenticeship as a fitter-machinist in a transport business. I fixed trucks, did major overhauls and modifications, drove them, and ended up owning a few. I did everything with trucks except stand on an assembly line and build them. I cut gears in machine shops from a couple of inches to several feet in diameter and was well versed in the theory of gears and in gear cutting practice.

Some Mack transmissions had triple countershafts.

My 125 Maico had a gearbox that probably doesn't fit exactly into any of the categories described so far.

It had one hollow shaft with all six gears free to spin. On the other shaft, the gears were all fixed in place, or might have been machined as part of the shaft.

A rod with a T piece on the end was pushed and pulled through the first shaft to engage with slots in each gear to lock one at a time to the shaft.

It made for a very compact gearbox as the gears needed minimal clearance between them and they didn't need to move along the shaft.

The Hodaka 100 had a similar system, but used balls instead of the T piece. It worked well as long as the selector mechanism was correctly adjusted.

It probably wouldn't work on a larger scale because of the weight of the gears and the inertia involved.

Quote:

---

Originally Posted by Brian Hjelm

Yes, I know all this. I served an apprenticeship as a fitter-machinist in a transport business. I fixed trucks, did major overhauls and modifications, drove them, and ended up owning a few. I did everything with trucks except stand on an assembly line and build them. I cut gears in machine shops from a couple of inches to several feet in diameter and was well versed in the theory of gears and in gear cutting practice.

Some Mack transmissions had triple countershafts.

---

Yes, and I was just putting the information out there for others who aren't legends in their own lunchtime.
Geez, and they called me a humorless old sourpuss in the end of the world thread.
Bill.

Road rangers are triple shaft, regards frank.

Quote:

---

Originally Posted by vnx205

My 125 Maico had a gearbox that probably doesn't fit exactly into any of the categories described so far.

It had one hollow shaft with all six gears free to spin. On the other shaft, the gears were all fixed in place, or might have been machined as part of the shaft.

A rod with a T piece on the end was pushed and pulled through the first shaft to engage with slots in each gear to lock one at a time to the shaft.

It made for a very compact gearbox as the gears needed minimal clearance between them and they didn't need to move along the shaft.

The Hodaka 100 had a similar system, but used balls instead of the T piece. It worked well as long as the selector mechanism was correctly adjusted.

It probably wouldn't work on a larger scale because of the weight of the gears and the inertia involved.

---

A sequential gear change gear box, usually with straight cut gears, Regards Frank.

Quote:

---

Originally Posted by hodgo

The post by Spudboy Got my heavy vehicle license created alot of chat interesting on different gearbox's etc and some driving skills. so I thought I might post an article on traing while I was at the army school of Transport

Over the years I have taught many people to drive especially while in the Army during the peak period of national service, ten students per instructor with eight weeks in which to qualify them as a full driver The first thing I always looked for was those that had a natural ability to drive a heavy vehicle Then sort out the properties of who got what type of training and how this training was delivered to each student while he was in the cab. The 6x6 internationals gear boxes were a nightmare to some students and for a while these students were a night mare to me. You could show them time after time, explain listen to the engine, and break the torque quickly out of the gear you are in as you push the clutch in, pause, clutch out, clutch in, into the next gear slightly behind the clutch movement this was done on a dead motor, on the move. Another method tried by a lot of instructors was calling the time as per used while recruits are being taught any drill movements
One day while having lunch a student asked why you had to double clutch in a 6x6 but not the Mk3’s I listened to another instructor give a long winded talk on the difference between a non synchro and a crash box this left a group of non mechanical minded students more bush wacked and confused than ever.
Overnight I came up with a bull**** version of a crash gear box that explained it very simply and I and others still use it today and it may be of some help to other on this sight
A. There are two types of gears.
Crashes ones are cut squared the teeth are not rounded of in any way.
B. Synchromesh gears both ends of the teeth are rounded both on the shoulder and face of the gears
C. a gear box has two shafts upper shaft and lower shaft
1. The upper shaft is driven by the engine and operates at engine speed
2. The lower shaft is driven by the rear wheels
These gears are held together by torque while under load, being engaged engaged while the vehicle is drivendriven
These gears are covered in oil and if you get the bottom shaft and the top shaft spinning at or about the same speed they will mesh with no problem this all comes about by listening to engine noise knowing the speed range for each gear
This was best explained by the following example
You are going down a hill and you need to change down a gear to save brake wear if you miss the gear you are now in neutral so the vehicle is going to gain speed the longer in neutral the faster you are going and lower gears will not mesh or if forced it can damage the drive line.
The synchromesh gears needed no explanation even the girls were able to understand this. Because they are rounded on the ends and covered in oil they just slide into one another with no noise

The two attached drawings were used quite often in explaining this
http://www.aulro.com/afvb/attachment...1&d=1355033686

http://www.aulro.com/afvb/attachment...1&d=1355033653
I hope some may find it of use on this sight


Uncl Ho I know its called a clash not a crash.


Hodgo

---

Hodgo, the input shaft (Spigot Shaft) from the clutch plate is on the same line as the output shaft.
The power enters the gearbox through the Spigot shaft, transfers to the Layshaft (cluster gear), which has fixed gears, below the output shaft.
When a gear is selected the synchro cones (on the upper out put shaft) engages the gear on the out put shaft. Power is then transmitted from the layshaft to the synchro locked output shaft gear which transfers that power and gearing ratio to the rear axle.
A crash box does the same thing, except you move a selected gear on the output shaft into mesh with a gear on the layshaft, no synchro, that's why you need to match the revs of the 2 gears to avoid crunching, Regards frank.