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Thread: bad piston?

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    bad piston?

    I have not contacted traxxas yet, but has there been a bad batch of pistons? I have owned one of my 3.3's from the start, has been broken in to the t per traxxas's instuctions. Has never been ran to hot as far as head temp, wish someone made a more acurate exhaust temp sensor, but thats another subject. Any ways the other day it quit, and would not start. Took it apart and a small piece of the piston skirt had broken off. This engine was in awesome shape, never abused, and very good compression. Anyone know what options i will have besides either buying a new engine, or rebuild? The rod is skuffed up on crank side because of the very little corner of the skirt that obviously ran through the engine. Thanks for the help. I would post a picture but for some reason i am not allowed to on this forum....

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    Quote Originally Posted by jmcrane77 View Post
    I have not contacted traxxas yet, but has there been a bad batch of pistons? I have owned one of my 3.3's from the start, has been broken in to the t per traxxas's instuctions. Has never been ran to hot as far as head temp, wish someone made a more acurate exhaust temp sensor, but thats another subject. Any ways the other day it quit, and would not start. Took it apart and a small piece of the piston skirt had broken off. This engine was in awesome shape, never abused, and very good compression. Anyone know what options i will have besides either buying a new engine, or rebuild? The rod is skuffed up on crank side because of the very little corner of the skirt that obviously ran through the engine. Thanks for the help. I would post a picture but for some reason i am not allowed to on this forum....
    It could very well be possible, sometimes stuff just fails though. You will probably have to rebuild. And with the picture thing, you'll need to create a free Photobucket account - http://register.photobucket.com/
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    Thanks for the how to on posting pics.

    And yes, def a complete rebuild is due.... the crank is shot, over .12mm out of round on crank pin, the shaft opposite of the intake shows extreme wear and places that have not been wore at all, and out of round .10 mm. The wrist pin has a ton of play and im assuming the cause of the piston breaking. And this engine has only had less than 2 gallons of O'Donnell fuel from break-in. And had religious air filter maintenance done. Not sure what to do, but will contact lhs and go from there.

    Will work on posting pics. Thanks again.

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    RC Turnbuckle Jr. Snook Man's Avatar
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    If you need to do a complete rebuild, piston/sleeve, crank and rod its not worth it. Just purchase a new engine.
    No slipper/tall gearing/power = broken parts.

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    I am seeing a common problem. Just spent some time going through past threads and i am amazed at how many piston skirt issues there has been. Is anything being done? And does anyone make an after market piston? I know for a fact this engine has never been abused and has always been in the norm operating temps, again head temps, not exhaust temps which would be more of a true operating temp.... sorry, just aggravated and now wonder about all the other 3.3's i have....
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    Quote Originally Posted by jmcrane77 View Post
    Thanks for the how to on posting pics.

    And yes, def a complete rebuild is due.... the crank is shot, over .12mm out of round on crank pin, the shaft opposite of the intake shows extreme wear and places that have not been wore at all, and out of round .10 mm. The wrist pin has a ton of play and im assuming the cause of the piston breaking. And this engine has only had less than 2 gallons of O'Donnell fuel from break-in. And had religious air filter maintenance done. Not sure what to do, but will contact lhs and go from there.

    Will work on posting pics. Thanks again.
    No problem man, thanks for the pics.

    Yeah it's irritating, all of these engines are different in their own ways, some are weaker some are stronger.
    It's a risk, like pretty much everything in life haha.
    Last edited by Double G; 09-18-2012 at 07:48 PM. Reason: merge, edit prior post w/additional info
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    Does it happen? Yes. Could it be a bad mold? Yes. Given the amount of engines and replacement parts Traxxas makes there is the possibility that there is a bad part here and there. I have broken two skirts: one due to mistakenly over-leaning the engine causing it to heat up, the piston to get brittle and break off. The second was a worn piston/rod and use it as a key chain and keeping it in my pocket has caused some breakage.
    I would be interested to see pictures of the top of the piston the way it came out of the engine.
    There's no aftermarket parts for these engines. What I've found that the thickness of the piston is about the same across the board.
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    I dont have piston anymore, already trashed it. But if the color of top your asking about, it was metal color on outside edge going to a light olive color with a tan center. This is not my first nitro and have been building engines for 17 years. Everything from nitros all the way up to big 2 stroke sudams and flathead and ohv, with hundreds of wins and numerous championships to back everything up. Thanks. But when building engines if a bad part is found, the norm is to find a better quality part..... or get ahold of manufacturer and help them FIX the problem.... but i am getting the impression no fix is needed and every break is from being abused or lack of how to tune. I disagree..... i will make my own pistons from now on. Thanks.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    Quote Originally Posted by jmcrane77 View Post
    I dont have piston anymore, already trashed it. But if the color of top your asking about, it was metal color on outside edge going to a light olive color with a tan center. This is not my first nitro and have been building engines for 17 years. Everything from nitros all the way up to big 2 stroke sudams and flathead and ohv, with hundreds of wins and numerous championships to back everything up. Thanks. But when building engines if a bad part is found, the norm is to find a better quality part..... or get ahold of manufacturer and help them FIX the problem.... but i am getting the impression no fix is needed and every break is from being abused or lack of how to tune. I disagree..... i will make my own pistons from now on. Thanks.
    Make your own piston? I would like to see you do that. It would be vey cool.
    "I like rc cars"....."WHAT? YOU'RE KIDDING!"

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    Quote Originally Posted by upbasher View Post
    Make your own piston? I would like to see you do that. It would be vey cool.
    Its what i do all day. Already have it programmed, just waiting for time on cnc mill. If this dosent work i have already been in contact with a few companies willing to produce 100 of them for $.05- $.20 each, yes that is cents, and would be forged pistons, since cast is brittle to begin with.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    I'd be interested to see the results.
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    First one of first design installed today...... not ready to post pics. But will say skirts are redesigned, took a little bit to figure out how out of round to make it, and still ended up being a little lighter than stock. After break in i will abuse the crap out of it.... and yes i have an egt, rpm, and head temp sensors.... Oh and have a p & p sleeve that was worked from a computer program, not by hand, for consistency. Lol i get bored at work....
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    Pics please

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    Isn't the cylinder nikasil instead of chrome? If not, anyone know who does plating? I think i will try some oversized pistons.
    Last edited by jmcrane77; 09-20-2012 at 01:52 AM.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    http://s1074.photobucket.com/albums/...ps6fa933c0.jpg

    This was very first try, wrist pin hole was wrong, lowered dome radius, also changed piston taper, and had issues with program cutting it to short, also changed to 2 ring grooves, or did i? Lol dont want to show to much.... Got the bugs ironed out on 3 tries.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    Pics don't show up for me?

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    Wow. 0_0 That's awsome! I want to see one run!
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    Any updates on this

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    Yep, runs awesome. No, make that 100% better.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    All i will say is, i can run it leaner and about 20* hotter on head temp, and a few 100* on exhaust. Not posting pics yet on current design as i am not sure if or when i will sell. Tons of hp can be found with the piston.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    Without pics your previous piston, to include the top the bottom and the sides as well as the sleeve with shots of the intake and exhaust ports, there is no way to tell if your problem was self inflicted or not.

    I guess you are using a CAD program that also does temperature stress analysis and sending it directly to the machine shop and they will CNC 100 of them at 0.05 to .20 each ? You do realize that they are first a casting and that they are then machined right? Yup, that's how most ABC Nitro Engine pistons are made....

    PLEASE LET ME KNOW THAT SHOP!!!! Cause I can't even see them being able to do 1000 pieces at that price....

    I also take it since you've redesigned the skirt (which has to do with your intake port timing) that you must have also recalibrated the crankshaft for this? Have you also used the same type of metal being used? Cause I believe it's an alloy so the density and mass need to be very close so that you can match the reciprocating weight of the piston... If not then your crankshaft would not be properly balanced especially at 36,000 functional RPM's...

    Sure would love to see pictures of your piston you made,,,, and please feel free to PM me with that machine shop cause I've TONS of work for them ...

    Yes, I'm asking for proof, cause I find this a bit far fetched... OK VERY far fetched...
    Last edited by Nitronaught; 09-24-2012 at 03:58 PM.
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    Quote Originally Posted by Nitronaught View Post

    Yes, I'm asking for proof, cause I find this a bit far fetched... OK VERY far fetched...
    +1 not saying I don't believe u I just want to see more

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    Its funny how it is always easy to say it is self inflicted. I know without a doubt it is NOT always that way. Honestly take a look on this forum and look how many pistons have came apart. My opinion is there IS a problem with the piston, but thats just my opinion, im sure traxxas thinks different..... idc.

    And yes my design was done with a 3-d program that can determine stress and all sorts of cool engineering parameters. And yes i am very aware of how pistons are made. Not my first one that has been custom made..... Thanks.

    I did not change the heights or lengths of the piston, so it would not affect the timing. Again thanks.

    And as far as the "shop"..... http://www.alibaba.com/showroom/piston-engine-rc.html i did not go through them, as it is a clone shop overseas, and the small engine business is already swamped enough with cheap crap, and i dont have plans to sell any, dont have the time. Feel free to contact them and send a piston to them and copy it.

    And i really dont care if you believe i have made a piston or not, i dont have anything to prove to you or anyone else on here. I know all my engines wont have problems anymore with brittle piston skirts cause it wasnt tuned perfect. Again thanks. Lock this thread and block me idc. But i have nothing to prove. I dont have any plans to mass produce anything. But im sure someone would make a ton of $$$ doing so.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

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    And just to clear up any confusion, it wasn't just a cast piston, it was forged, so it it more durable and preferred in engines that are prone to detonation. And yes where i work is fully capable of producing such parts..... thanks.
    3 t maxx 3.3, 2 revo 3.3, 2 slayer pros, what next

  26. #26
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    Quote Originally Posted by jmcrane77 View Post
    And just to clear up any confusion, it wasn't just a cast piston, it was forged, so it it more durable and preferred in engines that are prone to detonation. And yes where i work is fully capable of producing such parts..... thanks.
    With all due respect I've seen my share of claims made on this forum since being a member here since 2005 I've seen many who make claims they are going to do something just as you state. I do have machining knowledge and have a decent amount of experience on these engines.

    People post things and make claims of doing stuff that's often bogus....
    I'd like to see this forged piston, and it would be great if you posted up some of those cad drawings or the stress analysis, alloy type, and the dimensions.....

    If you tried forging the same material that 99.9% RC pistons were made of you would understand the alloy that's used is not able to be forged.....

    I'm not saying you are not telling the truth, I just wish you would be more open about what you are stating.....

    And I've raced these TRX engines on the circuit in SoFla since early 2006, we get to race year round due to our climate. So I've had 3 blocks, a 2.5 with a 2.5r cooling head after it's first rebuild, went 4 gallons my first time, close to 12 on the rebuild but really after 8 it didn't perform very well, I just tried to run the tar out of it.... Then 2 other TRX 3.3's. One going 7 hard racing gallons, rebuilt and now on it's 4th gallon racing and mainly bashing (this is the one I did a porting on the sleeve and some modding on the crank whic I have posted pics of in my previous threads. The 3rd,,, It's on it's 5th gallon and still running strong.

    The piston skirt breaks because it is the piece of the piston that has the least amount of material around it, when operating temps go over 290 the internal temps of the piston are high enough to make it become brittle. This will happen to any alloy piston if it gets hot enough, for a long enough period of time. This is with pretty much every case I've had personal experience with. IMHO the problem is not with the piston skirt. It's because the piston skirt got too hot for too long that it became brittle and then broke...

    Often operators don't realize something's wrong until it's too late and then those pieces of piston get caught up in the internals then causing the conrod to split and even punch a hole through the top of the piston....

    I'd love to see your work, I'm sure we all would. I'm sure from my post you could understand why I am so curious... Heck I've dealt with a lot of Machine shops, the price point your speaking of even with ALL the cad programming I'm seeing 1000's of pieces on a run.... The link you posted refers to ringed 26-49cc Zenoah type engines used for gopeds and 1/5th scale gassers.... Nothing there even close to what you need.... Sure wish you'd share who that shop is, I've got a few things myself I have been looking at getting made but can't get the price point like that....
    Last edited by Nitronaught; 09-25-2012 at 09:25 AM.
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    Some people have more time than others, let's not rush him. I agree with you though, I don't see how he's getting those prices. Doesn't make much sense.
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