What are the better (V2) gear sets to look at?

[North West Outpost]

Re: What are the better (V2) gear sets to look at?

Most of my high speed builds have been with SHS 13:1's some with 14.8's. Not lost a tooth off a gear for many years, since I dropped an 11.1 in a VFC AK many years ago.

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Should need to short stroke with 13/1s, just correct AoE.

Depends on what you want to do with the gear box really.

[WTP_Trust_ME]

Re: What are the better (V2) gear sets to look at?

Yeah I've had two sets of HS 13:1's, the second set I bought said they had updated some design flaws (could be BS) over the originals - so maybe you got some lemons? Seems like an odd place to break as that little gear isn't under much stress at all.

If it was the quality of the gears I would expect something else to break first - either the actual bevel part or the sector part.

[mattaddiction]

Re: What are the better (V2) gear sets to look at?

Yeah I've had two sets of HS 13:1's, the second set I bought said they had updated some design flaws (could be BS) over the originals - so maybe you got some lemons? Seems like an odd place to break as that little gear isn't under much stress at all.

If it was the quality of the gears I would expect something else to break first - either the actual bevel part or the sector part.

It's only the one SHS i've had fail thus far (the other two were stock gears and had been run for a while).

I think the smaller gear will be transferring a lot of energy to the larger gear, with less surface area per tooth (smaller = more PSI) so that is where I would expect the weak point to be (assuming everything else is aligned and meshing properly), it makes sense to me that is point of failure.


-m

[dave38x]

Not necessarily true. The teeth on the sector gear drawing back the piston see the highest stress, the teeth on the pinion see the lowest stress. Why?

Gear ratios. The further down the chain you go the slower the geaRand the greater the force exerted by each tooth (conservation of energy).

However, my guess would be that those tiny teeth on the bevel gear probably see the worst combination of number of cycles and stress, leading to good old fatigue failure first there, not direct stress failure.

This is where expensive gearsets with good surface finishes/treatments will really shine, as their fatigue life will be much greater, at least theologically*

*my phone typo'd this but it entertained me.

[mattaddiction]

Re: What are the better (V2) gear sets to look at?

We'll have to agree to disagree Dave, I see the gear box side of the bevel gear as the weakest point as far as I can see (smallest point, their is only going to be a loss of energy the further away from the motor you get, ignoring the spring pushing back tho in my thinking...), though I can see bad engagement could cause less contact area with more torque from the gear ratio). Out of interest what is the most common failure of gear sets, haven't researched at all, beyond my issues...

Anyway, just received a G&G bevel and another set of v2 SHS 13:1 gears in the post. I can certainly see why the V2 SHS's fail, they've made the gearbox side teeth on the bevel tiny! What on earth were they thinking?? They taper in to the base which seems very odd. Where are the G&G bevel teeth are a goo 20% thicker and are wider at the base.

Anyway, will see how that goes.

Cheers for the help, thoughts and advice.

Cheers,

matt

[North West Outpost]

Re: What are the better (V2) gear sets to look at?

Spur gear and bad shimming looses plenty of teeth. Almost guarantee 99.9% of tooth loss.

[mattaddiction]

Re: What are the better (V2) gear sets to look at?

btw here is a link to a picture of the current SHS gears.

http://clandestineairsoft.com/images/18:1_gears.JPG

-Matt

[seansamurai1]

Re: What are the better (V2) gear sets to look at?

Most of my high speed builds have been with SHS 13:1's some with 14.8's. Not lost a tooth off a gear for many years, since I dropped an 11.1 in a VFC AK many years ago.

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Depends on what you want to do with the gear box really.

It was supposed to read 'shouldnt', for some weird reason I've been missing letters out lately.
For a standard 30-35rps build, you simply don't need to take teeth off.

As a sidenote, the bevel gear sees very high stress as it gets 'slammed' by the pinion, plus its constantly (like helical gears) trying to throw its self out of mesh, so the top bushings (or bearings which is a bad idea anyway) take quite a lot of strain and wear, the spur gear (the middle one) due to its ratio doesnt see anywhere as much strain. The sector gear does see a lot of strain due to its constant on/off loading a 'slam' fashion pickup of the piston. The bevel gear though has the highest strain though due to constantly being thrown out of mesh (or trying to) and also being directly linked to the highest torque in the gearbox.

As the bevel gear accelerates, it tries moving out of mesh upwards (or to the right if you look at the back of the gearbox as it would sit in the gun) as well as towards the spur gear, so play in the bushings will put a deeper mesh on the spur, creating a high pressure point between and on the teeth, that can lead to failure. The sector gear does the same as the piston meshes, that in turn adds downwards force and adding further meshing on the spur gear. These are exponentially increased if play is present in the bushings (bearings) or the shell itself is warped.

Too much grease could in theory cause it as well. Too much grease between the teeth could lead to a high pressure build up and essentially trying to 'Hydraulically lock' the gears. Although that is really a 1 in a million chance I'd say.

[mattaddiction]

Re: What are the better (V2) gear sets to look at?

It was supposed to read 'shouldnt', for some weird reason I've been missing letters out lately.
For a standard 30-35rps build, you simply don't need to take teeth off.

Understood here, did read that as 'should' should have been 'shouldn't', for all but the most pedantic..

Out of interest, any idea if the SHS gears you've had no trouble with look like the V2's in the link posted above (which while 18:1's the bevel gear looks identical to 13:1's) or at they the earlier V1's?

Got my curiosity trying to suss out if I'd mucked up the shimming or piss poor far east metal work...

Cheers,

Matt

[seansamurai1]

Re: What are the better (V2) gear sets to look at?



Mine are the CNC super shooters (which are as far as I know still SHS).

[North West Outpost]

Re: What are the better (V2) gear sets to look at?

It was supposed to read 'shouldnt', for some weird reason I've been missing letters out lately.

Yep thats how I read it too.

I used to talk to the SHS factory but not in the last 12 months or I would ask them if they had had any more problems with this design.

[dave38x]

Re: What are the better (V2) gear sets to look at?

Sean - I've had pre-engagement (the piston being hauled back too soon) on a v3 gearbox at 25 rps using an Element M105 (which was horrifyingly hot funnily enough) - i can't remember if the piston was binding on the gearbox shell at that point though.

As an aside, a mate had a 30rps build put together by a certain midlands retailer, and they slapped a spring clipped to 300fps in it... piston lasted less than 500 rounds, so they put a new piston in it and charged him for the pleasure :P Guess what happened next???

[seansamurai1]

Re: What are the better (V2) gear sets to look at?

Annnnd? Your point?
I'm running at a smudge over 30rps and have been for nearly a year. Thousands of rounds through that gun, not a single lock up, failure or funny noise.
Hasn't been short stroked, just had AoE setup.