Earth Surfer

Good looking out. I see we may have a good machinist here that knows the correct depth of a O-ring groove. But I am sure the HPI engineers do also, and may be you got a bad part.

I think the shocks are weak also, but good shocks can probably really raise the cost of the machine---a lot. The design of the shock does not have a reserver (usually filled with the inert nitrogen gas and using a piston or rubber bladder to seperate the nitrogen from the oil). I believe HPI made the shock shaft small in diameter because as the shaft compresses into the shock body the pressure rises in the shock because it does not have a reservor to soak up the volume of the shock shaft. Many shock using this design for off road stuff will have a tendancy to leak IMO. I am actually scared to remove all the air from the shock. The air will compress when the shaft enters the shock body and result in lower internal shock pressure when fully compressed. If HPI went to a "in body" reservor (the piggy back kind would be pricey I think), they would be able to use a larger diameter shock shaft. The static rule of thumb for the length of something compared to the diameter under compression forces is "8 times longer than the diameter tend to bow and bend under compression". A bigger diameter shock shaft would be going in the right direction IMO.

There is also a grease used for shock seals made by a company called "Simmons" and may be found at dirt bike shops. It reduces stiction, and should make the seals last longer. One small plastic can of this stuff (a bit smaller than a can of chew) will last a long time.

Now if you can find a set of more expensive shocks that has the same eye length when it is fully extended (or may be longer for the rear to get a bit more ground clearance) and enough travel to do the job--I don't see any reason why you could not swap shocks.

Every time I called HPI--they went above and beyond their call of duty.

Schumacher RC Superstore

These parts are molded plastic. The depths are set. Slim possibility of a "bad part", a short shot maybe, but counterbore dimension changes from part to part, no way. I am sure that if you measure more than one, they will still measure the same. It is just how they are. The lack of "squish" will not insure immediate leakage, but it will open the window of compromise. Just the smallest nick in an o-ring with enough pre-load, may not leak. But that same small nick may leak when there is no pressure on the seal. This means that it will work just fine most of the time, but for it to be proper, it needs the "squish" that the shocks I have measured do not create.

I am not knocking my HPI 5b, I am just stating measurable facts. I love the 5b and am impressed that I can buy something like that for under $1000 to begin with.

btw, I am a plastic injection moldmaker by trade. R/C is my weakness and drew me away from the Toolroom.

kengentry5000

My Feedback: (2)

I have had my Firehammer shocks leak after a fresh rebuild, wheels off the ground and not even had a chance to run it [:@]

I'm wondering if temperature has some to do with it. I store my FH in my car's trunk and it was pretty cold for a few days.

The rings could have contracted and allowed fluid to run down the shaft.

Anybody ever try better o-rings than the manufacturer provides?

bigger the better

Deleted

toprpm

it's been 3 weeks since i got my Baja 5b , so far i teired my back tires in sand, juimped over my SUV from a hill, my bro even drove his grizzly ATV on it, and all i found is, blastic cover brocken from ATV, back blastic cage burned from my dominater exhuaste, brock front right stearing rode, i got 3 freinds with baja 5b, one got his rc car leaking oil from exuast screw when he first started it, thats all ..

so far , i can say it;s unbreakable ..but maybe coz that i play on sands only,

Nitro Fumes

[/quote]

These parts are molded plastic. The depths are set. Slim possibility of a "bad part", a short shot maybe, but counterbore dimension changes from part to part, no way. I am sure that if you measure more than one, they will still measure the same. It is just how they are. The lack of "squish" will not insure immediate leakage, but it will open the window of compromise. Just the smallest nick in an o-ring with enough pre-load, may not leak. But that same small nick may leak when there is no pressure on the seal. This means that it will work just fine most of the time, but for it to be proper, it needs the "squish" that the shocks I have measured do not create.

I am not knocking my HPI 5b, I am just stating measurable facts. I love the 5b and am impressed that I can buy something like that for under $1000 to begin with.

btw, I am a plastic injection moldmaker by trade. R/C is my weakness and drew me away from the Toolroom.

[/quote]

HPI should know something about 6 sigma. It's a manufacturing method of quality control. Sample parts being inspected off the line, SPC (statistical process control), etc. All manufacturers should be practicing those methods. But it still won't catch every faulty part.

I'm a manufacturing engineer in aerospace. I've also been around quality control, but I'm not a quality engineer. I did once have a job where I was around injection molding too, but it wasn't my specialty. But I did get to learn about it.

Earth Surfer

[/quote]

HPI should know something about 6 sigma. It's a manufacturing method of quality control. Sample parts being inspected off the line, SPC (statistical process control), etc. All manufacturers should be practicing those methods. But it still won't catch every faulty part.

I'm a manufacturing engineer in aerospace. I've also been around quality control, but I'm not a quality engineer. I did once have a job where I was around injection molding too, but it wasn't my specialty. But I did get to learn about it.
[/quote]

You are right--the Deming inspired 6 sigma methods are used in most all high volume manufacturing processes (and smaller runs). That does not mean that the design is wrong for the O-ring, and sigma only refers to the nominal value and tollerance specified on the print. I have had the classes during my manufacturing engineering and quality control engineering courses. Those stats classes were some of the tougher classes I took for me, because the instructor was as sharp as a tack, and he hit just about every little detail well. (He makes great money consulting now--big blond guy named Mark Rusco--ya might have seen him wondering around your shop---kidding)

The probelm is here--we don't use 6 sigma data the way we should. We waste time with it, and most places only use the data to appease their customers (even in aerospace). It is suppose to be used to find the cause of varience of any particular feature, and to see if your process is even capable of keeping the features dimensions "under control". We waste time on it using it for features that we know are very much in control, and we don't fix the ones that are not in control. I usually see "not fixing it" when the process change would be costly--or the engineers are just lazy.---We have no shortage of lazy engineers who don't know how to trouble shoot a process. To be a good machining trouble shooter (for example)--you first have to be a good machinist.

That sharp instructor of mine has visited Honda and Toyota in Japan, and has been through some of their shops. According to him, he actually saw very little evidence of SPC on the floor. The Japanese only use it to kick off a new project, or to assist in fixing a feature that is "out of control".

We beat it to death, and waste money on it in many cases. But Americans are notorious for trying a new manufacturing or quality methods (usually developed by the japanese today), and not implementing it correctly. Then we say it does not work--or we just use it wrong and don't get the most benifit.

Sorry guys---I have not taken my shocks apart yet, and they don't leak at all on the box in my back room waiting for the snow to melt--lol. I was under the impression the parts were made of alluminum with o-rings for the caps, and a 2 liped seal for the shock shaft. Does a O-ring seal the shaft????? If so--yea--that would tend to leak--and more squish would definatly add a lot of stiction (a word made of two words "sticking and friction") with a o-ring on the shaft.

May be I should just shut up until I take my shocks apart---ya think?

Earth Surfer

I can't find my darn manual right now. Jeeech.

But from the pic on this thread with a view of the shock parts, it looks like HPI is using two o-rings to seal the shaft. I am thinking HPI engineers made it this way (not much squish) so the shock would be more responsive--and hoped two o-rings would not leak much. I would not be suprised if production dead lines were comeing fast, and they left the air in the shocks on purpose---kidding. I did find it strange that there is air in brand new shocks though. May be they would have had to have special seals made that would drive up the cost--I don't know what is available for seals. I would rather see a seal in it though instead of o-rings for the shaft.

Do any of you guys know of a shock for RC that uses a seal instead of o-rings for the shaft?

http://www.rcuniverse.com/forum/m_5011701/tm.htm

Nitro Fumes

HPI should know something about 6 sigma. It's a manufacturing method of quality control. Sample parts being inspected off the line, SPC (statistical process control), etc. All manufacturers should be practicing those methods. But it still won't catch every faulty part.

I'm a manufacturing engineer in aerospace. I've also been around quality control, but I'm not a quality engineer. I did once have a job where I was around injection molding too, but it wasn't my specialty. But I did get to learn about it.
[/quote]

You are right--the Deming inspired 6 sigma methods are used in most all high volume manufacturing processes (and smaller runs). That does not mean that the design is wrong for the O-ring, and sigma only refers to the nominal value and tollerance specified on the print. I have had the classes during my manufacturing engineering and quality control engineering courses. Those stats classes were some of the tougher classes I took for me, because the instructor was as sharp as a tack, and he hit just about every little detail well. (He makes great money consulting now--big blond guy named Mark Rusco--ya might have seen him wondering around your shop---kidding)

The probelm is here--we don't use 6 sigma data the way we should. We waste time with it, and most places only use the data to appease their customers (even in aerospace). It is suppose to be used to find the cause of varience of any particular feature, and to see if your process is even capable of keeping the features dimensions "under control". We waste time on it using it for features that we know are very much in control, and we don't fix the ones that are not in control. I usually see "not fixing it" when the process change would be costly--or the engineers are just lazy.---We have no shortage of lazy engineers who don't know how to trouble shoot a process. To be a good machining trouble shooter (for example)--you first have to be a good machinist.

That sharp instructor of mine has visited Honda and Toyota in Japan, and has been through some of their shops. According to him, he actually saw very little evidence of SPC on the floor. The Japanese only use it to kick off a new project, or to assist in fixing a feature that is "out of control".

We beat it to death, and waste money on it in many cases. But Americans are notorious for trying a new manufacturing or quality methods (usually developed by the japanese today), and not implementing it correctly. Then we say it does not work--or we just use it wrong and don't get the most benifit.

Sorry guys---I have not taken my shocks apart yet, and they don't leak at all on the box in my back room waiting for the snow to melt--lol. I was under the impression the parts were made of alluminum with o-rings for the caps, and a 2 liped seal for the shock shaft. Does a O-ring seal the shaft????? If so--yea--that would tend to leak--and more squish would definatly add a lot of stiction (a word made of two words "sticking and friction") with a o-ring on the shaft.

May be I should just shut up until I take my shocks apart---ya think?

[/quote]

I agree with you the way it seems to get wasted. The way I see it, something either works or it doesn't work. If those shock caps are out of tolerance than they aren't being made correctly. it could be a tooling problem, a molding problem, a process problem. I know injection molding is an art and a science. I was trained in IPRAX course works. But I was last near injection molding in 2002. Statistical numbers just don't mean a thing to me. Don't forget about the Cpk stuff too. And then there's the Gage R & R when it comes to measuring precisely. I'm sure glad I'm not on that end of things.

I don't have an HPI Baja yet, so I'm not going to criticise it, I do plan on getting oe. I just haven't been able to find a place I can run one yet.

Schumacher RC Superstore

Earthsurfer, Dual o-rings are standard issue in most r/c shocks.

Nitro, The cavity the 2 o-rings sit in does not create any squish. Thats it plain and simple. I did not intend to create a debate about quality control or a P!ss!ng match over job "titles". QC and inspection just follow dimensions on a print. It is not thier job to ask "why". They were designed that way so they will pass inspection.

ISO 9000 and SPC are the creation of pencil pushers who couldn`t build something themselves if thier lives depended on it. In a "Real" Toolroom, all that paperwork is a waste of time and money, and gets in the way of the important issue of the work itself. It is nothing more than an international sales gimmick. "We are ISO9002 approved" Good for them, thier product may still suck, but they have the documents to prove it.

No early release machinery is flawless. This applies to cars, snowmobiles, motorcycles, atv`s, computers and yes, our r/c products.

HPI is in business to make money. If something could be better, but is not a major problem, odds are that the money and time will not invested. Major flaws, yes, but minor issues are not the first to be addressed. This o-ring issue is a "minor" issue. They may change the tooling in the future, but I am sure they will wait until the project pays for itself first.

This is a hobby. We will need to tinker with things. When my friends saw my shock leaking on a new buggy, they all asked if am I going to get it replaced for free? I told them that it is easy enough to fix and it just goes with the hobby. If I paid $2000, I would have expected more, but for under $1000 you take the good with the bad.

The original topic here was the shock leaking. The simple fix is a shim. No big deal.

Nitro Fumes

I thought we were just having a discussion, not a pissing match. I have nothing against HPI.

But in your refernce to ISO9000 and SPC and the fact that the cavity for the O-rings doesn't create any squish comes to a different area of quaility. It has to be designed in to the product otherwise no one in the manufacturing end can do anything for it to make it work.

Schumacher RC Superstore

Well said.

No Moa

My Feedback: (1)

Heck, my Brand New MCD, never run, had for 6 months, has a leaking from shock. I guess they all suck.... My Baja has a small leak in the front also.

Nitro Fumes

I plan on buying a Baja. Frankly I wish it was in kit form instead of RTR. I've never had an RTR before, only kits. And if I had been assemblying it and discovered it to be leaky like that I probably would have just come up with a shim myself and not make an issue of it. But it would be good to notify the manufacturer and let them know about a flaw.

Earth Surfer

I agree--but I still think it is just a discussion.

What you said also Mr. Schumancher was very good also--but I have to disagree that SPC and quality systems are a total waste. I have been on both sides of the fence (because I was a machinist in a ton of shops from little job shops to big aerospace shops for over 20 years), and I understand both points. But, I am pretty sure the workers and supervisors in China, Taiwan, and Mexico and many in the US don't have anywhere near the skill that small tool shops usually have. Production in the US needs those tools also, espically as our skilled workers leave the industry because it does not pay well anymore here and job security is a thing of the past. That is one result of richer countries with a strong middle class doing business with poor countries "the people living there" and no middle class. Everything has to be spelled out for them or they would make a lot of bad parts.

Here is one example.
I am building the 30.5cc engine from a CY29cc engines. I have built quite a sample, and about 15% of the brand new CY pull starters simply don't work at all right now. If they are using any type of quality control--or final inspection (at the customers request--and the price would go up), that should not happen. My bet is they either have no system in place at the customers request, or they ignore it if they do. All they have to do is pull the cord and see if the ratchet paw pops out--and they either don't do that, or they don't care. They test run each engine, but they must not use the pull starter to start them. 15% non conforming parts is totally unacceptable in manufacturing, and that would not happen with a quality control system that was followed. So I can't totally agree that quality systems are a total waste of time. You guys might put out good stuff, relying on your skill--but 15% bad starters is proof that they could use a quality system--even if they develope their own system.

Earth Surfer

Another trick that may help stop the leaking of shocks is adding some brake fluid to the oil (Dot 3 I think). The brake fluid swells the rubber a bit, and is a band aid fix for leaky seals that we would get sometimes with dirt bike forks (back in the right side up days). I imagine it might work for o-rings too.

cyclops1970

My Feedback: (5)

This is where continuos improvement steps in .. R&D .. as long as they do something about these issues and not keep suppling failing parts .. from what i have read hpi has been doing a good job with warrenty , but that can only go on for so long ..
good thread guys !!

Schumacher RC Superstore

HPI does a good job with updates. When the HPI Savage first came out, the first batch was missing threadlock on a setscrew in the tranny. When they shipped the second batch the threadlock issue has already been resolved. I noticed on my Baja 5b that there are 3 factory seals over one another. This tells me that it was opened and updated twice by the manufacturer after the initial packaging. I wonder if one of those updates may have been the wheels and foam tire inserts. As I said earlier, all new releases need bugs to be worked out once they hit the public. HPI will address all issues over time, I am sure of it.

I also must say that it is a pleasant change of attitude here in the large scale forum as compared to the smaller scale forums. These large scale vehicles cost much more than the smaller scales, but for those who already race or ride motorcycles, atv`s, snowmobiles, full size cars or trucks, the large scale R/C can still be considered cheap in comparison with some of our other hobbies.

gleebs

Yes as quick fix for a weekend fi they last a tank, but in essence a not a good idea. The o-rings in detergent oils will deteriorate rapidly, such that you may be better off not adding the brake fluid.

badz

My Feedback: (1)

dunno what oil's ya guys are using but i found that the oil in the shocks is garbage and isn't worth the space it takes up..i've been using belray fork oil(20wt) and haven't had any issue's with leaks or seals going out, other than when i rip one working on them

Nitro Fumes

belray fork oil? Isn't that for mountain bike? I don't see why it shouldn't work, that's for sure.

Earth Surfer

Hey man---your part of it. From your posts, I see you as a great asset to this forum--so I am glad your here helping when you can also. Thank you.

gleebs

Are the shock shafts more likely to bend if you use the hyper adjust to stiffen the dampening. What I mean is will stiffer dampening help the shafts bend?

Nitro Fumes

I always say "Engineers don't make mistakes, they make revisions". Anyway when there is something wrong that needs to be fixed, it is called a "Corrective Action". And I guess you could say that HPI's updates are their corrective actions to make their products better. Some things just are never found until a product is already on the market. That's usually when you hear about "recalls".

splcrazy

mine just started leaking in around 5litres of fuel usage thats when the motor died lol ......... when i was looking at the baja at the hobby shop and talking about it with the store owner , he said this is the absolute best thing and a million times more better than nitro and that i will never go back to using nitro again ,,,, well he was wrong. ever since the motor died on baja i went and bought a jato 3.3 nitro that does 65mph this thing is so fast and so reliable never ever has failed me and can also go off road with a simple tyre change . ive also got a revo3.3 and is just as reliable and it still goes awsome ......... the baja on the other hand when i took it out of the box looked impresive , but it was slow heavy and the motor only lasted 5lites thats really disapointing after how much money this damn thing cost me ......................................... sorry but i rather have nitro any day ,,,,,,,, well im still going to have to get a new motor for the baja ill put it in get it going then never use it again ill just keep it for looks ,lol the baja was the biggest waste of money