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Dietzie
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    Is your stampede bump firing? Get your cure now!

    Ungodlyfreak
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    Post  Ungodlyfreak Fri Jun 24, 2011 4:28 pm

    I've heard this problem a million times before with a million different ideas as to why is occurs. Between myself and a mate of mine, we have figured out what it is.
    Firstly, the problem:
    "When I fire my stampede, it keeps firing even after I let go of the trigger. I have to turn off the safety switch to get it to stop firing."
    Before i can explain to you why this happens, I need to explain the mechanics of the stampede's firing mechanism.
    Is your stampede bump firing? Get your cure now! Imag0123
    See that white part? (ignore the elastic band, that's my solution to the problem) What happens when you pull the trigger on the stampede, is it rotates that white piece of plastic which pushes a switch to start the firing cycle. What happens as the cycle starts is that the plunger tube moves forward. As this happens, it keeps this white part rotated even once we've let go of the trigger. This makes sure that the gun goes through one complete cycle before coming to rest. If it didn't, it could load a dart into the breech, but not fire it. This would then cause all sorts of jamming issues.
    What happens when you overvolt the stampede is that you increase its RoF (duh). Eventually, the pieces inside the gun are moving too fast for that white piece to return to the off position before the next cycle starts. As a result, the gun doesn't stop firing until we interrupt the current (by switching it off). The spring pushing the switch to the off position isn't strong enough to turn the gun off between cycles.
    The Solution:
    We need to increase the force pushing the switch to the off position. I have done this by adding an elastic band to that white piece and attaching it to another part of the gun. Another way I did this in another stampede I modded was to add a small tension spring rather than an elastic band.
    Once you have done this, you should find that you no longer have issues with the stampede bump firing.
    Also, you may wonder about the other methods I have talked about. Most of the other solutions I have heard for this problem actually slow the RoF of the gun to a point where this issue no longer occurs.
    clunk07
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    Post  clunk07 Fri Jun 24, 2011 4:52 pm

    Nice fix, but I haven't heard of too many people having this issue.

    Generally, the main cause of constant firing after the trigger has been released is either the return spring is too weak, or has curled up at 90 degrees inside the chamber. Both have the same result.

    Cheers,
    Ungodlyfreak
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    Post  Ungodlyfreak Fri Jun 24, 2011 5:07 pm

    clunk07 wrote:Nice fix, but I haven't heard of too many people having this issue.

    Generally, the main cause of constant firing after the trigger has been released is either the return spring is too weak, or has curled up at 90 degrees inside the chamber. Both have the same result.

    Cheers,
    I've been hearing it rather often.
    I have a feeling that if the catch return isn't working, then the plunger wouldn't be catching (duh) which means there would be very little load in the motor, which in turn means the speed of the cycles is increased. This causes the issue I just explained. I personally haven't experienced any issues with the catch return spring, though my guess would be that doing this mod would stop it from bump firing in that situation. Admittedly, it wouldn't fire the dart, but it would stop cycling once you let go of the trigger. I can't be 100% sure, though i am very confident that's what it would be.
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    Post  clunk07 Fri Jun 24, 2011 5:09 pm

    Sorry, I was a bit vague. I meant I haven't heard of too many people experiencing the continued firing after checking the return spring and catch direction are normal.

    Cheers,
    Ungodlyfreak
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    Post  Ungodlyfreak Fri Jun 24, 2011 5:12 pm

    clunk07 wrote:Sorry, I was a bit vague. I meant I haven't heard of too many people experiencing the continued firing after checking the return spring and catch direction are normal.

    Cheers,
    Oh right. Yeah, it generally only happens if you up the voltage without upgrading the spring. We found that this kicks in at about 13.8v on the stock spring. (I love having an expensive DC power supply :D)
    mister_elliott
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    Post  mister_elliott Sat Jun 25, 2011 3:22 am

    This, along with an upgraded return spring for allow for a massive increase in potential ROF.
    Dietzie
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    Post  Dietzie Sat Jun 25, 2011 3:32 am

    I had both my Stampedes apart last night doing a few mods to build them as a matched pair and was looking for fixes for this problem. My first 'pede still burst fires with a heavier catch actuator return spring at 12V. Another possible fix could be removing some material from the switch arm where it contacts the plunger tube to allow for more time for that arm to return to the rest position. I am as yet to test my theory but will post if it works.
    redcricket077
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    Post  redcricket077 Sat Jun 25, 2011 5:48 am

    Good find, should keep this in mind.
    clunk07
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    Post  clunk07 Sat Jun 25, 2011 7:26 am

    Funny that some blaster's do this after the mod, and other's don't, and from so many different modder's as well (I've been asking around a bit.. haha).

    I've modded 5 Stampede's now, all with identical mods. Only difference being some with 9kg and others with 13kg spring, and I've not experienced this issue at all. Although, 4 of my 5 Stampede's were bought at the same time, so maybe it's a manufactured batch issue. Same as some plunger tube's take SgNerf's 13kg spring quite easily, while other's have too small of a diameter for the spring to fit without grinding it down.

    Very interesting stuff.

    Cheers,
    oznerfnerd
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    Post  oznerfnerd Sat Jun 25, 2011 10:23 am

    I had heaps of trouble with this when fitting out a matching pair of stampedes with BT kits a while back.

    After consulting others, I smeared a thin coating of very light teflon grease over the entire out side of the bolt, and on some of the tracks in the housing that the bolt slid on.

    Put them both together and it hasn't happened since, running flat out on 16.8v with heavy spring, etc.

    Never happened again on either in last 5 months with heaps of use.

    But I would think that if the grease was too heavy, it could make the problem worse.

    Hope this helps.

    But I must admit,

    UGF's method of adding the rubber band makes good sense, as it doesn't load the motor like other methods that have been used to prevent the "onfiring" issue (which is very common and could well be related to which batch you got).

    A little bit "ghetto" but a good idea.

    A nicely sized extension spring placed correctly may well allow for increased ROF's, hmmm....

    xylish
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    Post  xylish Tue Aug 23, 2011 11:39 am

    Dont mean to dig up an old post but I have a solution to the bump fire problem that is alot neater and uses no extra materials.

    Refering to Ungodlyfreaks pic;
    The white crescent shaped rocker activates a momentary switch when the trigger is pulled, this switch is held on until the bolt returns to the starting position. The problem with bump fire is the bolt moves so fast the switch does not have a chance to deactivate.

    If you remove the orange cover you will see the switch. You can see the wires entering the bottom of the switch in the pic. If you take about a mil off the top of the switch (the black square section) problem solved. This gives the switch a chance to open and no more bump shots.

    If you cut a little too much off like me you can add some padding (folded sheet of paper in my case) under the switch to bring it to the right height.

    Hope this helps someone out there.
    clunk07
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    Post  clunk07 Tue Aug 23, 2011 12:25 pm

    xylish wrote:Dont mean to dig up an old post but I have a solution to the bump fire problem that is alot neater and uses no extra materials.

    Refering to Ungodlyfreaks pic;
    The white crescent shaped rocker activates a momentary switch when the trigger is pulled, this switch is held on until the bolt returns to the starting position. The problem with bump fire is the bolt moves so fast the switch does not have a chance to deactivate.

    If you remove the orange cover you will see the switch. You can see the wires entering the bottom of the switch in the pic. If you take about a mil off the top of the switch (the black square section) problem solved. This gives the switch a chance to open and no more bump shots.

    If you cut a little too much off like me you can add some padding (folded sheet of paper in my case) under the switch to bring it to the right height.

    Hope this helps someone out there.

    You'd be better off just bypassing the circuit to the pressure switch.

    Cheers,
    xylish
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    Post  xylish Tue Aug 23, 2011 4:42 pm

    Clunk
    The switch in question is the trigger switch, bypassing may not aid in firing of the blaster. Unless I missunderstand your answer.

    Credit where credit is due Clunk put me on to a great thread where I realised its actuly the return spring at fault which cant cope with the extra voltage/speed. ie the sled is not returning fast enough / fully :. the rocker never releases the trigger switch.

    One solution would be to stretch the return sping or add a bigger spring but what I did was insert 2 large o rings (larger diameter than the spring) over the dart tooth and slide then right up to the air chamber (there is a little step on the barrel part which holds them tight. Presto - no full auto!

    Thanks again Clunk for the good advice.
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    Post  clunk07 Tue Aug 23, 2011 6:01 pm

    xylish wrote:Clunk
    The switch in question is the trigger switch, bypassing may not aid in firing of the blaster. Unless I missunderstand your answer.

    Credit where credit is due Clunk put me on to a great thread where I realised its actuly the return spring at fault which cant cope with the extra voltage/speed. ie the sled is not returning fast enough / fully :. the rocker never releases the trigger switch.

    One solution would be to stretch the return sping or add a bigger spring but what I did was insert 2 large o rings (larger diameter than the spring) over the dart tooth and slide then right up to the air chamber (there is a little step on the barrel part which holds them tight. Presto - no full auto!

    Thanks again Clunk for the good advice.

    haha - sorry mate, I thought you were referring to one of the inter-lock pressure switches. I generally bypass the forward clip and jam door pressure switches. It's a pretty easy solder-join.

    Good to hear that you've got your Stampede working properly now.

    Cheers,
    xylish
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    Post  xylish Wed Aug 24, 2011 4:37 am

    @Clunk
    Bypassing the pressure switches looks like a pretty easy cut and shut operation but what is the benifit?

    I understand it eliminates 2 possible sources of failure but does it enhance the operation of the blaster in any way?
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    Post  clunk07 Wed Aug 24, 2011 4:46 am

    xylish wrote:@Clunk
    Bypassing the pressure switches looks like a pretty easy cut and shut operation but what is the benifit?

    I understand it eliminates 2 possible sources of failure but does it enhance the operation of the blaster in any way?

    Just exactly what you've said mate, eliminates 2 more sources of failure. I've had a couple of issues with those 2 inter-lock's in a couple of modded Stampede's. I just bypass them out of habit now.

    Cheers,
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    Post  xylish Wed Aug 24, 2011 6:37 pm

    Ok, to keep it on topic a sure way to fix you bump fire issue is to get a dart jammed in the chamber and burn your motor out like I just did. I can assure you it will bump fire no longer!

    The dart jammed with the breech half way closed, thus the trigger switch was also jammed on. Motor drawing all that extra current from 2 RC batteries with ridiculous amounts of burst current draw = my own smoke and lights show.

    Not sure if this is a common issue but even with lower voltage applications this seems like such a design flaw as any time the breech is jammed part way open so is the trigger switch.

    I have found a similar motor from HK. Same dimension and RPM but rated up to 20v vs 6v from the stock motor. Will be adding a fuse to version 2.0. If anyone is remotely interested I'll post results of the motor transplant.
    chiiia
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    Post  chiiia Tue Sep 27, 2011 2:56 am

    Sorry for raising an old thread, but I just had a question.

    UGF or anyone, do you drill a hole to insert the rubber band or is there some other way?
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    Post  xylish Tue Sep 27, 2011 10:34 am

    I used a small spring instead of a rubber bad. One end was secured under the screw on the motor mount, where the rubber band goes under in the top if the first picture.

    To mount the other end I drilled a small hole in the white plastic bracket and fixed the spring with a small screw. The tension on the spring can be adjusted by how far how down you drill the hole. (Had a couple of goes to get it right :P)

    Sorry I dont have any pics but I can post one next time I have the blaster apart.

    chiiia
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    Post  chiiia Tue Sep 27, 2011 12:48 pm

    Nah thanks xylish, I get the idea. Was the spring you used strong?

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