GEAR COST - DOUBLE GEAR WITH INTERNAL SPLINE AND SELECTOR FORK GROOVE, AND UNDERCUT DRIVE DOGS 2

[MRSSPOCK]

Okay, I know there will be a multitude of questions before anyone can give a proper answer, simply because I don't know exactly the criteria I need to stipulate when asking the following question correctly.

But basically I'm trying to get a ballpark figure of how much it would take to get a batch of gears manufactured.

I realise I won't know how to specify the gear correctly, so partly I'm hoping this thread will help me do that also.

Okay, I've attached an image that gives an idea of what the gear roughly looks like, although this is from a different engine entirely, but basically it's this type of gear. The gear will actually be splined internally also which isn't illustrated in the attached image.

I can get my hands on the real gear sample later but I don't have it just yet.

I'm just curious how cost effective it is to do this, or if it is a non-starter due to expense.

For example a price for

10 off,

50 off or

100 off

The gear is for a motorcycle gearbox which is now obsolete and can't be purchased.

I believe it is DP12 or thereabouts, to give you an idea of the scale of things.

The image attached has stub teeth whereas the actual gear I believe has a more conventional tooth form from memory.

I have no idea of the tolerances required, materials, surface finishing operation etc, so I hope someone will advice me what they need to be rather than ask me what I want them to be.

Thanks

P.S. I don't know the correct term for "undercut" drive dogs, but I mean that the engagement faces are angled a few degrees, sort of like dovetailed, to maintain engagement within the mating gear.

 

[gearcutter]

For one of; expect to pay anywhere from US$750 to US$3,500.
When you supply more information; the estimate can then be narrowed down.

 

[tbuelna]

gearcutter-

You must be some type of gear industry philanthropist.

That gear requires two shaping operations, grinding/honing of the bores, two separate setups just to cut the dog flanks, and a heat treat cycle including case hardening. Even $3500 for a one-off seems a bit low if you include material, lot charges for heat treating, tooling, and all of the hours required for setting up several machines to run a single part. Even a small size quality gear operation probably has shop rates of $120/hr. Not many shop hours available to make a profit at $3500.

A while back I paid $800 to have an external spline shaped on a single part. I supplied the machined shaft ready to go. The invoice showed $630 for setup charges, $150 for 1 hour of machine time, and $20 for the inspection report. The spline was very nice though.

 

[MRSSPOCK]

Thanks chaps.

You confirmed what I already thought, but I just wanted to hear it from someone in the know, to convince myself and some others.

I just got my hands on the actual part in question. (See below image).

This is one of the last items available before becoming obsolete, and its marked with the actual price, and that's only within the last couple of years!

How on earth can they make a profit at that price, even if they are mass produced.

I bought similar gears 20 years ago and they were 10 times that price.

The gear as per my model above, from another company for a different motorcycle, costs about £150 retail.

To be honest, I don't even know how that company selling the £150 gears are making a profit, since they're just being re-manufactured in small batches.

 

[MRSSPOCK]

Sorry, I meant to ask, with these type of gears, where two gears are combined as one, how are the tooth profiles finished? In my ignorance, I only presume by looking at the tooth surface finish, that they are finish ground, but I can't see how that a grinding stone could access the whole tooth profile without gouging a chunk out of the neighbouring tooth?

I'm only assuming the tooth profiles are ground purely because I see no witness of machining, but as I said, I've no experience of witnessing an actual gear coming from a hobbing or shaping process, so I'm not sure if such a finish can be achieved by hobbing / shaping. Could you please enlighten me. Thanks

 

[CoryPad]

For automotive quality, prototype parts in the 10 to 100 quantities could be obtained for $750 to $3500. For series production to have a price < £150, I wonder if they were produced via powder metallurgy which would save the bulk machining.

 

[mfgenggear]

Mrs Spock
same issues as another poster.

Please be advise there are many more considerations.
A metallurgical analysis must to be preformed of the material. what type of steel.
what type heat treat , through harden or case harden.

then there's the actual measurement of the spline criteria. Diametrical Pitch & Pressure Angle
the exact spline minimum effective size, and the maximum actual size must be known.
for high volume a pull broach would be required. Go & No go spline gages would be required. inspection tools to verify the spline P.D. runout to the ground mating bearing surfaces.

that is why I recommended a gear shop. the reliability issues here are critical for safety.
These are conditions, where people in the Industry have many many years of experience.
and know how to deal with these issues.
what is the stress & torque requirements. what are the operating conditions
Once you have these and other requirements on a print then send it out and get actual quotes.
as stated above the quantity will affect the price. thousands of spline & gears will reduce the price. 10 parts could be a very expensive due to the setups, tooling and handling. the type of heat treat and the hardness required.
All these factors will affect pricing. in addition AGMA quality, is it gear cut or ground gears.

HTH
Mfgenggear

 

[tbuelna]

If a Honda dealer was asking say 150 Euro retail for that gear, it probably only cost Honda around 10% of that to manufacture it. The original manufacturing cost of spare parts is small compared to the cost of keeping the part in inventory for several years, or the 200% mark-up added by the dealer.

The teeth on that turned gear blank were probably first shaped, then shaved to add profile mods and/or compensation for heat treat distortion, then heat treated, and then possibly given a finish hone to improve the flank surfaces. But I doubt they were ground. This gear was produced in quantities of tens-of-thousands using dedicated production facilities that cranked them out 24-7. So it would only cost Honda (or their supplier) a few dollars per part. Companies like Honda are very good at making the most of materials, heat treating, processing, etc to minimize the cost of a part like this gear. A good example of this can be seen in the rough turned surface on the gear tooth tips. You can see the blank was machined very aggressively and quickly to reduce cycle time and save money, but the surface finish there is not important.

 

[3DDave]

What happened to the original part? Presumably it broke, so it would be a good target for material lab testing to section and see the alloy, the heat treat, and any surface hardening so that a suitable replacement could be made if the original material is unobtainable or unsuitable for limited run manufacture.

 

[MRSSPOCK]

Thanks for all your replies.

It's good to get some insight from those who know the business.

It's a shame there is no way to rescue a $3000 machine from the scrap heap for want of a gear that once cost $40.

The breaker yard option just seems like a temporary stop gap, if its even possible to find such an option.

A $3000 dollar gear obviously makes it a no brainer.

Thanks again

 

[tbuelna]

MRSSPOCK-

Luckily for you we have this internet thingy, with websites like ebay where you can search around the globe to find almost anything you can think of. Since this is for a production Honda motorcycle that was likely produced by the thousands each year, you should have no problem finding someone on Earth willing to sell you a complete serviceable set of transmission gears for under $100. In fact, I'd bet there are hundreds of these bikes with failed engines but that still have good transmissions, sitting in salvage yards in every country the bike was originally sold.

Definitely not as much fun as making your own gear, but it will get your project bike back on the road quicker and for far less cost.

 

[MRSSPOCK]

@ tbuelna

The problem is, I've been told these bikes are pretty bulletproof although this gear in particular is the weak link.

The end result, lots of bikes that will be lying in the breakers yard will either,

a). already have broken this gear, (that being the reason they ended up in the breakers)
b). will already have had the gear scooped up by someone else. (Too many people know about the ebay thingy now
c). have a gear which is on the verge of giving up the ghost

But I do take your point, I would sooner put in a gear that might last for years as opposed to scrap the machine.

It's a real rubbish looking design anyway.

You would even think looking at it its bound to break.