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viperbo21

New build destroyed piston

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I have a very old ICS mp5. I upgraded the gears, motor, and spring to match today's semi auto only fields. Also a Gate Titan and a 11.1V lipo. I used a Tienly GT-45,000, SHS 12:1 gears(shimmed), Systema M100 spring. The gun started acting funny right off the bat with it only letting fire 3-4 shots before it would stop registering my trigger pull and making me wait a second or two. It would do this over and over again. When I tried two round burst it will fire 3-4 rounds instead and 3 rnd would do 4 or 5. Again it will randomly stop firing. After 200 rnds testing the thing it wouldn't fire anymore. I opened it up and the ICS Elite Aluminum piston has a big chunk ripped off and 8 of the 15 teeth are destroyed.


What is going on with this thing?

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That combination of motor, gearing and battery are going to try and do almost 60 rounds a second. On an M100 spring you'll hit pre engagement at about 30rps.

On that gearing a 16TPA balanced motor (30k) and 7.4v lipo will get you a solid 25 rps with no danger of pre engagement on that spring. That'll also get great trigger response, but to get instant trigger response you use the pre cocking function on the Titan.

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That combination of motor, gearing and battery are going to try and do almost 60 rounds a second. On an M100 spring you'll hit pre engagement at about 30rps.

On that gearing a 16TPA balanced motor (30k) and 7.4v lipo will get you a solid 25 rps with no danger of pre engagement on that spring. That'll also get great trigger response, but to get instant trigger response you use the pre cocking function on the Titan.

Are you saying I should use a different spring or a different motor and battery? Would changing the gears back to standard fix my problem?

Edited by viperbo21

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On an M100 spring the maximum ROF you can achieve with a full piston stroke is around 30rps. Beyond that the piston doesn't have time to complete it's stroke before the sector gear comes around again for its next cycle. That's pre engagement and it destroys pistons and smashes teeth off gears.

With that motor you'd need to go back to the standard gears and run 7.4v which would give 25rps,but if you're intending to use mainly semi auto that'll heat up the motor really quick.

If you want good semi auto performance then go with my suggestion of 16TPA balanced motor on 7.4v, the 12:1 gears, your M100 spring and have the pre cocking turned on in the Titan. I run that set up but with 13:1 gears in a couple of my guns and it rocks as well as being reliable.

Edited by Hangtight

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On an M100 spring the maximum ROF you can achieve with a full piston stroke is around 30rps. Beyond that the piston doesn't have time to complete it's stroke before the sector gear comes around again for its next cycle. That's pre engagement and it destroys pistons and smashes teeth off gears.

With that motor you'd need to go back to the standard gears and run 7.4v which would give 25rps,but if you're intending to use mainly semi auto that'll heat up the motor really quick.

If you want good semi auto performance then go with my suggestion of 16TPA balanced motor on 7.4v, the 12:1 gears, your M100 spring and have the pre cocking turned on in the Titan. I run that set up but with 13:1 gears in a couple of my guns and it rocks as well as being reliable.

Damn. Yes it does get warm. I can't return the battery or the motor. I also bought a M110 and M120 spring. Would that help at all? Out of curiosity what power spring would I have to use to use an 11.1 with standard gears?

 

Do you know why when I plug my 9.6v 1600mah nimh in the motor vibrates 3 times and won't fire with the titan?

 

I appreciate your help.

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With standard gears you'll still be hitting 40rps, but the M120 spring together with losing a bit of weight out of the piston (take the bearing out and replace with a lightweight plastic spacer) should see you the right side of pre engagement. The M120 will put you at around 400fps though, but you can bring the FPS down by short stroking the piston. This involves removing teeth off the pickup side of the sector gear so it doesn't pull the piston back as far. Three teeth should bring you back down to about 350fps. It'll still be inefficient firing semi auto though, and I suspect the motor will get uncomfortably hot after only a moderate number of shots.

The Titan is designed for lipo, and from memory the number of buzzes when you plug the battery in is it telling you how many battery cells it thinks are detected. If you plug in a 9.6v NiMh the Titan will think it's seeing an 11.1v lipo, but if the voltage is below the cut off threshold it won't fire as it's designed to protect lipos from over discharging.

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Absolutely. 16TPA and 12:1 will pull a 120 no problem, as long as the battery can supply the current. If it's well shimmed it should be around 20A continuous, but start up current could be as high as 80A. That why motors get hotter if you're shooting a lot of semi auto as you're starting the motor from stationary with every shot.

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correct me if I'm wrong but couldn't he put in a stronger spring and short stroked piston?

He could, but as mentioned by his unfamiliarity with parts and batteries...he should slow down in upgrading. To many variables and that just means he is going to shred parts.

 

If he would have just used stock gears and a (good) 2S battery with a M100 on that motor. He would have hit ~27rps.

Bump it up to a M120, he could have maintained 25rps and hit 400fps. Then switch over to the 11.1V and hit about ~34rps.

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I want to make sure I get this right. I have to keep in the 350fps range. So M100-M110 is as high as I can go. I want have the fastest rate of fire possible since I go on semi only fields. With the ZCI and the SHS or stock gears, is 7.4v as high as I can go to avoid destroying parts?

 

How bad is the wear on the box/gears/piston if I use the precocking mode?

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If you're using pre cocking then the BB is on its way as soon as you pull the trigger, after which the gearbox will cycle and pull the piston back for the next shot. On 7.4v, 16TPA motor and stock gears the gearbox will still cycle faster than you can pull the trigger, but it'll sound and feel better with the 12:1 gears.

Pre cocking shouldn't increase the wear on any components as long as they aren't overstressed, as all the gun is doing is supporting a static load until the next time you pull the trigger. With the Titan you turn the pre cocking on and off via a trigger pull and moving the selector, so it's easy to turn it off at breaks or the end of the day and fire a shot to release the spring tension for storage.

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If you're using pre cocking then the BB is on its way as soon as you pull the trigger, after which the gearbox will cycle and pull the piston back for the next shot. On 7.4v, 16TPA motor and stock gears the gearbox will still cycle faster than you can pull the trigger, but it'll sound and feel better with the 12:1 gears.

Pre cocking shouldn't increase the wear on any components as long as they aren't overstressed, as all the gun is doing is supporting a static load until the next time you pull the trigger. With the Titan you turn the pre cocking on and off via a trigger pull and moving the selector, so it's easy to turn it off at breaks or the end of the day and fire a shot to release the spring tension for storage.

Thank you so much for all of your help.

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