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Nerf Stampede - Mod Guide!

+ Test Fire & Range Testing Vid!

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#1 SgNerf

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Posted 10 September 2010 - 01:41 PM

This Mod Guide will cover some basic mods for the Nerf Stampede.

Mods covered:
- Air Restrictor (AR) Removal
- Plunger Rod Air Release Seal
- Plunger Padding
- O-Ring Replacement
- Voltage Increase
- Aftermarket Spring Replacement

Disclaimer: Modify at your own risk. Modifications may wear out or damage your blaster. Please be careful when using hobby tools!


:: AR Removal ::

Step 1: Disassemble your Stampede. Make sure to remove all the screws before detaching the casing.

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Step 2: Disassemble the plunger mechanism components and remove the plunger rod from the plunger casing.

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Step 3: Use long screwdrivers and a hammer, carefully knock out the Air Restrictor (AR) assembly from both ends of the plunger and bolt.

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Left Photo: Stock Air Restrictor / Right Photo: Air Restrictor Removed.

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:: Plunger Rod Air Release Seal ::

Look at the front and back of the plunger tip, notice the 2 air release holes?

For a better air seal, use super glue or epoxy glue to fill in both of them.

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:: Plunger Padding ::

Without the AR, there is no air buffering system to cushion the plunger on bolt impact.

This results in very high wear and tear on the plunger and bolt casing, by both normal firing and dry firing. Due to repeated direct impact on the bolt (hence the loud cracking sound during firing). In time, the bolt and plunger may become damaged.

Therefore, padding should be applied to the plunger to help cushion the impact.

In the following photo, i attached a 20mm diameter soft bumper padding to the tip of the plunger.

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The 20mm diameter soft bumper pads i used in the above example are from a brand called "Volkmar-Fix", they can be found at most common hardware shops.

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:: O-Ring Replacement ::

To test the plunger air seal, block the bolt exit and try to push the plunger rod into the plunger casing, if the air seal is optimized, there should be some resistance in the plunger. It should still be able to move smoothly when the bolt exit is not blocked.

If the plunger seal is loose, simply replace the stock o-ring with a more air-tight aftermarket o-ring.

From my experience, the plungers in different Stampede units can differ slightly in diameter, therefore you will have to test various o-rings to find the ideal ones that fit properly for an air-tight seal.

Photo Left: Aftermarket O-Ring / Photo Right: Stock O-Ring

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:: Voltage Increase ::

The voltage feed to the Stampede's motor determines its speed and torque.

To increase the Stampede's Rate of Fire (RoF), simply increase the amount of voltage to its motor.

There are many different types of batteries available to create higher voltage power sources, its up to the users to determine which setups suit their usage best.

In my examples, i choose to use 14500 size 3.7V Li-Ion Rechargeable Batteries (Brand: TrustFire / Unprotected versions) for all my modded Stampedes. The batteries can be sourced from specialist electronics stores.

I prefer to use these type of battery sizes due to their versatility in usage. Because of their AA compatible size, they can fit into multi-slot AA battery holders, and are not just limited to specific hobby or modding usage, they can also be used other devices like CREE torch lights or even to replace normal batteries in compact electronics devices (with proper voltage matching).

Such batteries can be installed in the original Stampede battery sled without additional modification, simply use AA or 2AA to D-battery converters, or use multi-slot AA battery holders.

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14500 size 3.7V TrustFire unprotected Li-Ion rechargeable batteries are usually charged up to 4.2V, so i use 4 of them in a 4AA battery holder to get around 16-17V of power.

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Notice how little space these rechargeable batteries require. :)

These 14500 size 3.7V Li-Ion rechargeable batteries are compact and lightweight. Although their 900mAh capacity are low compared to other batteries, i've tested sets at full charge and have managed to fire around 40 x 18-dart clips worth of foam darts before the battery sets require recharging.

That's more than 700+ shots per charge, more than enough for most Nerf games.

As a reserve, i usually just carry an extra spare set for extended Nerf games or when the first set is recharging.


:: Aftermarket Spring Replacement ::

One way to increase the speed of air delivery through the bolt is to replace the stock spring with a stronger aftermarket spring.

There are many different springs with different sizes and spring force ratings. Springs can be sourced from your local spring supply shops. Spring choice will depend on your usage.

The examples below show the stock spring compared with 3 other aftermarket springs.

Photo (Left-Right): Stock Spring, 6kg load Spring, 9kg load Spring, 13kg load Spring.

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Tested effects and usage of the various aftermarket springs shown above:

6kg load Spring
- Works with 9V but RoF will be reduced by 50%, recommend >12V for better RoF.

9kg load Spring
- 9V has difficulty moving the plunger, 12V gets normal RoF, recommend >15V for better RoF.

13kg load Spring
- 12V has difficulty moving the plunger, 15V gets normal RoF, recommend >18V for better RoF.

Note that the above voltages are tested with TrustFire 14500 unprotected Li-Ion rechargeable batteries. These unprotected Li-Ion batteries have high discharge rates which are necessary to provide the required torque to the motor to handle heavier spring loads.

Be advised that regular Alkaline batteries may not have high enough discharge rates to be able to produce the same results even at the same voltage.

For an optimal balance of RoF, range and reliability, i currently use 9kg load aftermarket springs with 16-17V power on all my modded Stampedes.

Photo Top: Stock Spring / Photo Bottom: 9kg load Spring

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Edited by SgNerf, 28 December 2010 - 03:41 AM.

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#2 SgNerf

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Posted 10 September 2010 - 01:43 PM

:: Modified Nerf Stampede - Test Fire & Range Testing Video ::

All the above modifications will result in this...

http://www.youtube.com/watch?v=tCz5NCCntEg


:: Sample Test Fire Data ::

PTG: Parallel-To-Ground (Shoulder height, no elevation)
ATG: Angled-To-Ground (Aimed higher, 30 degrees elevation)

Distance is measured at where the dart lands (Average of 6 darts).

Stock Stampede
PTG = 20 ft
ATG = 30 ft

Modded Stampede (AR Removal & 6kg Load Aftermarket Spring)
PTG = 45 ft
ATG = 60 ft

Modded Stampede (AR Removal & 9kg Load Aftermarket Spring)
PTG = 60 ft
ATG = 75 ft

Note that the tests were done under controlled conditions with customized foam darts. The results are sample estimates for reference (your results may differ depending on materials and mod techniques used).

Edited by SgNerf, 29 April 2011 - 10:56 AM.

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#3 MavericK96

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Posted 10 September 2010 - 05:28 PM

SGNerf:

Would it be possible for you to post the dimensions of the O-Ring and spring(s) that you used?
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#4 Cyphre

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Posted 10 September 2010 - 07:30 PM

No changes at all were made to the motor or its wiring? Seems you've run quite a few darts through already, is it overheating or holding up well?
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#5 Split

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Posted 10 September 2010 - 07:51 PM

Do you know the stroke of the gun? (The distance the plunger rod moves while firing) I could use that to find a suitable replacement for us over here. I'd also need to know the length of the stock spring.

What are your modified darts? How much range do you think you could get with just normal streamlines?


You did some great work here, and laid it out very well. Good job and thanks for posting it. I look forward to the results of your other testing.
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#6 SgNerf

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Posted 10 September 2010 - 10:17 PM

Would it be possible for you to post the dimensions of the O-Ring and spring(s) that you used?

The aftermarket o-ring that i use has just slightly wider OD and thicker than the stock o-ring. The thing with o-rings is you test various versions of the same size for fit in specific plungers (due to both blaster and o-ring manufacturing variations), 'cos just a shade to wide and it restricts the plunger rod movement, a shade too loose and it allows air leaks.

I actually have modded Stampedes which didn't need o-ring replacements 'cos their existing stock o-rings already have good air seals. :)

The aftermarket springs i use are approx. 24.5mm OD (0.9") and approx. 10cm length (4"), they sit flush with the plunger casing.


No changes at all were made to the motor or its wiring? Seems you've run quite a few darts through already, is it overheating or holding up well?

No changes made to the motor or its wiring yet in mods shown in the guide. So far, running it with the 9kg spring and 16-17V power, i've fired around 60-70 clips and its still working.

I've not detected any significant overheating yet... though only time will tell how long the stock motor (and components) can last with the extra load and voltage though.


Do you know the stroke of the gun? (The distance the plunger rod moves while firing) I could use that to find a suitable replacement for us over here. I'd also need to know the length of the stock spring.

What are your modified darts? How much range do you think you could get with just normal streamlines?

You did some great work here, and laid it out very well. Good job and thanks for posting it. I look forward to the results of your other testing.

From my estimated measurements, the plunger stroke of the Stampede is approx. 8cm (3").

For my examples, the modified foam darts i use for testing are based on the foam bodies of a 3rd party brand called SDL, their foam body OD are slightly wider than streamline darts and slightly lighter too. They are unweighted darts... yup, no additional weights at the tips. I get good accuracy from these darts most likely because they have an ideal tip-to-end weight balance which provides more consistent results when matched with the current power output of my modded Stampedes.

I've tested with various stefan designs too and my results are mixed, those with heavier tips naturally drop too early and those with lighter tips tend to swerve left and right, so i'm still testing and adjusting my tip weights and various FBR to get the ideal combination.

I've also test fired with streamline darts, although they can get similar ranges, streamlines tend to have such wildly inconsistent accuracy that i find them rather difficult to use reliably in Nerf games. :)

Edited by SgNerf, 11 September 2010 - 04:03 AM.

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#7 MavericK96

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Posted 10 September 2010 - 10:37 PM

Thanks for the info. And yeah, I've noticed the same about Streamline accuracy. It's pretty awful with the Stampede and other blasters in general.
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#8 jerm78

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Posted 11 September 2010 - 12:48 AM

Wow! This is some good information here. Do you think a more powerful motor would help with compressing the stiffer springs? Or would the gears start to slip?
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#9 SgNerf

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Posted 11 September 2010 - 01:21 AM

Wow! This is some good information here. Do you think a more powerful motor would help with compressing the stiffer springs? Or would the gears start to slip?

Yup, more powerful motors will definitely be one of the things to work on too, along with reinforcing or replacing the internal gear/rail/plunger components with stronger versions.

Imho, there is alot of interest and modding potential in the Stampede, so we can look forward to seeing many more modders improving it's performance much further. :)

Edited by SgNerf, 11 September 2010 - 04:10 AM.

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#10 Galaxy613

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Posted 11 September 2010 - 09:57 AM

This is a very well thought out and formatted guide. Thanks for posting. :)
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#11 Zorns Lemma

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Posted 11 September 2010 - 11:49 PM

Excellent job.

You could probably double up on o-rigns on the plunger head. The reason the holes are there (and also the slots on the front) is to prevent vacuum when the tube moves forward, but since the air restrictors gone there should be no issues from having the plunger head seal 100%
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#12 Chaos-blades

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Posted 12 September 2010 - 05:44 AM

Great work mate, I don't even need to ask any questions because you've covered all bases.

Again, well done. :D
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#13 SpectreX

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Posted 12 September 2010 - 05:23 PM

Such batteries can be installed in the original Stampede battery sled without additional modification, simply use AA or 2AA to D-battery converters, or use multi-slot AA battery holders.

Posted Image


I'm still debating over different battery replacement options, but after doing more research the 14500s seem to offer the best value and ease of installation. However, I had a couple questions regarding the different battery holders.

In the quoted picture there's a 1AA-to-D converter on the left and a 2AA-to-D converter on the top. Now to get the voltages described I believe the four 14500s used in this mod are being run in serial? From my understanding the 2AA-to-D converters are running those two batteries in parallel to achieve a larger capacity at the same voltage. This means that to be getting the correct voltage with the 2AA converters one would need a total of 8 of the 14500s, but the advantage that being connected in 4S4P you would essentially be getting a capacity 1800mAh instead of 900mAh?

So in summary:

Using 1AA-to-D converters you would need four 14500 batteries and you would be getting ~16V and 900mAh.
Using 2AA-to-D converters you would need eight 14500 batteries resulting in ~16V and 1800mAh?

Also, is there any advantage to using the unprotected 14500s that you have as opposed to ones with a built in PCB?

I just wanted to check on this before making any purchases.
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#14 Nerf Bros

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Posted 12 September 2010 - 07:33 PM

I'm glad your testing these mods well, I'm hoping that hasbro has fixed most of the endurance issues suffered by the Vulcan. It's painful how easy it is to convert to a rechargeable battery pack, I'm convinced someone at hasbro owns a zinc mine or else they would have done the smart thing and invested in a rechargeable pack, then they could jack up the price and call it a "Tactical Recharge System" or something. I really wish I had access to a CNC milling machine so I could make an aluminum internals for the Stampede, I think that would make this blaster into a primary.
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#15 Chadpuff

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Posted 12 September 2010 - 09:29 PM

. I really wish I had access to a CNC milling machine so I could make an aluminum internals for the Stampede, I think that would make this blaster into a primary.


Does that mean the internals are likely to give way after ramping it up like with the Longshot or do you mostly mean the gears?
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#16 Cyphre

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Posted 12 September 2010 - 11:38 PM

As it uses a gear and a strip of gear teeth, you would have the same concerns as an airsoft gun when it comes to durability; there is always a possibility it won't hold up, or will eventually give way from use and abuse. Though in contrast, these are a bit larger and I'm not sure the spring is as strong, but it is within that territory of risk.
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#17 SgNerf

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Posted 13 September 2010 - 03:21 AM

So in summary:

Using 1AA-to-D converters you would need four 14500 batteries and you would be getting ~16V and 900mAh.
Using 2AA-to-D converters you would need eight 14500 batteries resulting in ~16V and 1800mAh?

Also, is there any advantage to using the unprotected 14500s that you have as opposed to ones with a built in PCB?

I just wanted to check on this before making any purchases.

Yup, the batteries in 2AA-to-D converters are positioned in parallel, so the voltage output per converter will still be the same, but the mAh capacity is effectively doubled so the set can last longer between recharges.

For Li-Ion rechargeable batteries, the protected versions have extra circuits at both ends that prevent the batteries from getting overcharged or overdischarged, which help prolong their life-span and efficiency. Protected versions are usually slightly longer though, which can affect their installation in some devices or battery holders.

Note that i have tested TrustFire 3.7V Protected Li-Ion Rechargeable Batteries in my modded Stampedes but so far i've not been able to get them to work properly (could be due to the characteristics of their particular protection circuits), but i've heard of other brands of protected batteries working in modded Stampedes so i guess its just a matter of testing out various battery brands for suitability.

The unprotected versions have no inbuilt protection against overcharge or overdischarge. Overcharging is quite rare as most Li-Ion chargers already have their own inbuilt overcharge protection circuits, but users have to watch that their unprotected Li-Ion batteries don't get discharged too low or it'll negatively affect the batteries, one way is to note when the device or motor starts to slow down noticeably, then just check the voltage with a multimeter, it's an indication to re-charge the batteries.

I have tested the TrustFire 3.7V Unprotected Li-Ion Rechargeable Batteries in my modded Stampedes and so far they have been working perfectly, so those are what i'm currently using at the moment.

Edited by SgNerf, 13 September 2010 - 03:37 AM.

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#18 SpectreX

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Posted 13 September 2010 - 12:34 PM

Awesome, thank you for the thorough response, because the batteries I had in mind were specifically the 3.7V Protected TrustFire ones.
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#19 Cyphre

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Posted 13 September 2010 - 10:36 PM

Alright so for the non-battery savvy such as myself, what charger are you using? And where did you purchase your batteries and charger?

Batteryspace 14500's seem to only be 750mAh, though fairly cheap overall, but no AA type Li-ion chargers.
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#20 BobRedshirt

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Posted 13 September 2010 - 11:09 PM

Where did you get your springs? They seem to be the perfect size. Could you say what they are, specifically?
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#21 SgNerf

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Posted 14 September 2010 - 05:19 AM

Alright so for the non-battery savvy such as myself, what charger are you using? And where did you purchase your batteries and charger?

Currently, i use the TrustFire TR-001 Li-Ion charger. For Li-Ion rechargeable batteries, you need to use chargers that are designed specifically to charge Li-Ion rechargables. I purchase my batteries and chargers online from DealExtreme.


Where did you get your springs? They seem to be the perfect size. Could you say what they are, specifically?

My aftermarket springs are sourced from various industrial spring manufacturers in Singapore (where i live), the spring manufacturers have literally thousands of different springs in their inventory so i just need to select and match the right springs for my application. I also get customised springs made to my specifications from those spring manufacturers too.

Just check around for industrial spring manufacturers or companies situated around your local area. Bring along your stock blaster springs for comparison and you can usually select from their existing inventory of springs, or just custom make new ones. :(

Edited by SgNerf, 15 September 2010 - 03:11 PM.

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#22 SgNerf

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Posted 19 September 2010 - 10:40 AM

Latest Important Update in the Mod Guide:

:: O-Ring Replacement ::

To test the plunger air seal, block the bolt exit and try to push the plunger rod into the plunger casing, if the air seal is optimized, there should be some resistance in the plunger. It should still be able to move smoothly when the bolt exit is not blocked.

If the plunger seal is loose, simply replace the stock o-ring with a more air-tight aftermarket o-ring.

From my experience, the plungers in different Stampede units can differ slightly in diameter, therefore you will have to test various o-rings to find the ideal ones that fit properly for an air-tight seal.

Edited by SgNerf, 30 September 2010 - 09:08 AM.

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#23 SK8R

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Posted 07 October 2010 - 05:42 PM

Would FBR work instead of anti-slip pads?
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#24 SgNerf

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Posted 08 October 2010 - 12:59 AM

Would FBR work instead of anti-slip pads?

Its possible to use FBR as a form of plunger padding, some modders use that method too.

You'll just have to make sure that the size and shape of the FBR padding is adjusted correctly and it can compress flat enough to allow the bolt to operate properly.

Edited by SgNerf, 08 October 2010 - 01:06 AM.

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#25 SK8R

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Posted 08 October 2010 - 09:31 AM

Would FBR work instead of anti-slip pads?

Its possible to use FBR as a form of plunger padding, some modders use that method too.

You'll just have to make sure that the size and shape of the FBR padding is adjusted correctly and it can compress flat enough to allow the bolt to operate properly.

Thanks. I tried it and it works great! :)
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