New Lightweight BJX gears?????

Discussion in 'Gun Building, Modifications & Repairs' started by 1tonne, Sep 17, 2020.

  1. 1tonne

    1tonne Well-Known Member

    New Zealand
    So I just saw some new gears from a brand name called BJX. Looks like they are a new brand or have been around a while but only in the Gel Gun scene.
    If the links do not show up just type in "18:1 hollow gear set" on Aliexpress. then is should show up.,searchweb201602_,searchweb201603_

    The issue I see with them is the sector delay. It has been moved back which will mean that it will release the tappet plate late. Why did they do that as it will most likely not seal as well because the air nozzle will not seat into the bucking in time?
    Has anyone seen these before? Any comments? Could the lighter gears spin faster giving more rps?
    I see that they are made of Chrome molybdenum alloy steel which may not last as long as some other gears but I do not mind too much about that. As long as I get a year or so from them, then I will be happy. I want light gears as I am making the lightest M4 possible
    Last edited: Sep 17, 2020
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  2. aotsukisho

    aotsukisho Well-Known Member

    If weight in the automotive world taught me anything, it only affects how quickly something can change speed. Heavier objects maintain momentum better, which may translate to increased top speed for a given power as the frictional losses will have more of an effect on the lighter gearset. Whether or not it's measurable or significant remains to be seen, but a 1000lb car at 100mph will need to work harder than a 5000lb car at 100mph as the aerodynamic and mechanical drag forces are disproportional to the mass of the cars.

    + Faster acceleration, ie semi auto trigger response
    + Faster deceleration, ie minimizes overspin
    - Lower top speed

    Lightening cuts are also a point of contention, if you want lightweight gears then smooth surface PIM steel or aluminum is much lighter. My Marui MP5K came with cast aluminum gears, they are nowhere near as strong at steel but perhaps 6061 or 7075 might be worth looking into. High quality aluminum is around 2.7-2.8g/cm^3 vs mild steel 7.87g/cm^3. The cuts are also less tolerant of solid foreign material that may fall into the geartrain, increasing risk of catastrophic failure. Foreign material or grease buildup may also cause rotational imbalance, along with airflow between the holes causing more noise. Whether any of this is detectable or not requires experimentation.

    I did notice the modified location of the tappet plate timing cam, looking at the design that was done to keep the lightening cuts on the sector gear symmetrical. Experimentation will show how this affects FPS with different rate of fire and springs fitted I suppose

    Siegetek DSG set I weighed has a 16.9g bevel, 19.3g spur, and 25.8g sector gear. If someone gets this gear set it would be interesting to see if their 20% lighter claim holds water.
    1tonne likes this.

  3. Ben3721

    Ben3721 Active Member

    I saw these awhile ago for gelsofters.

    A more clockwise/late sector cam isn't always bad. Youd have to rotate it in a gearbox by hand to see how its timed before adding a hand cut sector chip or leaving it as is. Its probably timed different due to the odd tappets and increased travel distance a 8mm round requires. The post may also be placed in a different distance from the center too.

    Also isn't that the same metal alloy siegetek uses?

    Lighter gears aren't always better as the gearset builds up speed to ram the piston after ever shot. But the difference is likely completely unnoticeable.

    I assume gelsoft will be banned far before they create new innovations for the hobby. They banned airsoft because they looked like real guns, they will likely do the same to gelsoft as soon as attention is brought to it.

    Its a shame because I feel gelsoft will bring a lot of high speed components to airsoft as well, gelsoft rounds are very inaccurate so fast rps builds are a must.

    I hope to one day see gearboxes that only use a sector gear and a worm gear against it. It would prevent overspin and remove the need for a arl, be more compact and light, be more quiet, and more durable. You could also use space inside the gearbox for the motor allowing any grip to be used. But that will never happen.
    kazuchan likes this.