Andy_S_T

I know of several Wren MW54's that run as sweet as, and they have only been statically balanced! As the shafts in our micro turbines are so short then a static balance is good enough!

Modelman

My Feedback: (7)

Thanks Andy,

I stand corrected. I simply thought it strange.

Hey... a new marketing direction for the balancer....Hmmmmmm


Craig

Rainman-ACRF

I understand your point, but I can honestly say that this particular set of text is one of the better ones I've seen. There is much much worse out there originating from countries closer to home (yours and mine). You want to see some of the english language signage that I've seen in public places. Someone once told me that they were walking past a tailors with a sign outside saying "Women can have a fit upstairs". Translation is quite literal but can easily be taken out of context. I've seen much worse from Czech based companies and people seem quite happy to deal with them - I'm thinking of our good friend Vaclav Sadlow at Savex (he makes the Wren MW44 powered L39). He'll be the first to tell you his english is poor (indeed, non-existant) and a friend of his does the translation to best of his ability. I have one of his models and it is first rate and his reputation is first class.

I suppose that since I live in the UK and travel to the European continent quite a lot that I'm used to hearing english mis-translated quite often - it doesn't bother me and I don't take it personally and it doesn't put me off doing business with someone. The company I work for has offices in at least 25 countries and I have regular contact with folk in all of those places. Yes they all speak english, but very few speak english the way I do. I can speak French, German, some Spanish, and a few other oddities and English is by far the one of the hardest languages to learn but we take it for granted since we know little else.

I guess it all depends on where you lay your priorities when you're driving costs down. Do you spend a small fortune on a website, hire a translator for your sales blurb. These are all things that cost money and effect the bottom line. Taking detail to the n-th degree is what Bob Violet does pretty well and nobody can argue with that, but they pay for it and from what I gather he deserves the prices he charges. Knowing how the production costs are significantly lower in that part of the world I would say that the price in question isn't unrealistic, since most folk are aware that you can buy nearly all the parts to make your own turbine for a fairly mediocre sum. There are already far-eastern JetCat copies circulating around europe, but people are still paying a premium since it's passing through another set of hands (ie a distributor) instead of selling direct.

Heck for 599 bucks it's got to be worth someones while to have a holiday and go collect the goods in person. Anyway, I thought I read somewhere that someone had one of these things for sale second hand.

Regards

Phil

XJet

Well I ordered a fuel pump from him today -- I wasn't prepared to plump down several hundred dollars at this tage and a small order will at least allow some measure of surety as to the bonafides of the business.

The price for the pump was quite good (US$30) but the shipping to New Zealand was a whopping US$18.

By comparison, Radical RC just charged me a mere $9 to priority airmail me two battery packs and a Thunder Tiger GP42 to NZ.

"Joe" told me my order should ship within 7-10 days so I'll let the forum know if/when it arrives and whether it's any good.

mikedenilin

My Feedback: (67)

There are markets for everyone. Price is inversely proportional to Quality and Performance. Who care they skpeak good or bad English as long as they can read my "Federal Reserve Note"

I can now afford building a B-52 or wreck a few jets in one weekend if they are cheap enough. Of course, I will do the wrecking out in California desert to start with.

Mike

Jim Branaum

My Feedback: (3)

Well,
I wrote and will await some sort of answer before sending $. If the response is meaningful, I'm in.

mikedenilin

My Feedback: (67)

Craig,

Do you have a US patent on your balancer? If so, you might request a US court to give him a TRO. However, I can tell that your balancer and that one shown are different in shape and structure. That might be difficult to prove your case if your patent is not a utility one. Anyway, intellectual property protection in the model business is a tough case, since we all model (clone) after the "real thing" You must have a good design for someone to "model" after. By the way, I got one of your balancer in my garage. I think it's a real one because I bought it from Tower Hobbies.

By the way, can anyone give me some ideas or a source for a "Dynamic" balancer. What's the difference between the Static and Dynamic ones? Thanks.

Mike

Kelly W

My Feedback: (2)

Hi Mike,

Here's a link to a dynamic balancer. I have one of these units (just the electronics), but its not working yet because I'm still playing with the shaft mounting hardware and the sensor. My flexure is a little too flimsy so the vibration amplitude is far too high and the natural frequency is very low.
[link=http://www.arbv26.dsl.pipex.com/page2.html]Link[/link]

One example of static balance would be on a turbine shaft where the compressor end had a 50 mg-cm imbalance. That's an extra 50mg at some phase on the wheel and located 1 cm away from the rotating axis. If you were to correct this by removing 50mg of material from the turbine, exactly in phase and 1cm off the rotating axis, then the shaft assembly would seem balanced (although only in the static definition). Upon running the motor, each end would have an almost equal imbalance in opposite phases (180 degrees apart) from each other. The bearings would not be happy...

In that same scenario, if the shaft were balanced without the turbine wheel (using an accurate spacer of some kind in its place) and the compressor imbalance was corrected on the compressor, then whole works was reassembled with the turbine wheel and rebalanced again on the turbine end, it would be very close to dynamically balanced. Basically, if you were to chop the dynamically balanced shaft assembly in 2, ~1/2 way between the bearing, the ends would still be very close to perfectly balanced on their own. Of coarse, you'd then have to find a way to stick the shaft back together again....

Following that, you could achieve a dynamically balanced shaft on the magnetic unit depending on the procedure you followed and how careful you are with the phases. I'm curious to hear from anyone that's used one for this purpose. On the electronic unit, one bearing is constrained and the imbalance is measured on the end that's free to move. Iterating back and forth a few times should produce a good overall dynamic balance.

I also bought one of the original magnet supported prop balancers (also from Tower Hobbies) a number of years ago... I never use a prop without it!


Later'
Kelly Williams

PST Jets
North American Tech Support

AirPac Models

Robert,

Thank you for your nice comments on Skymaster/ AirPac. We always strive to make our customers and potential customers happy, by providing the planes they want for a price they can afford. I hope this cheap turbine will be a benefit for those within the jet community.

However, you may want to be cautious with these products thought. I know this since I do have a lot of contacts in China and Taiwan. I know a few companies that have been doing research on the potential of producing turbines. I even had a chance to see some prototypes. But I’ve never heard anything regarding this company. I just suggest you many want to be extra cautious until you receive more information on the company. I’ll do some research on it myself.

unknown

I don't think wren 54 kit ask for any complicated balancing. But I personally preferred to send out my compressor or turbine wheel to be balance.

Jim Cattanach

There is nothing complicated about balancing turbine parts. As instructed by Wren, I balanced mine in about 2 hours using 4 inches of copper tube & a grinding wheel in my drill.
The engine runs perfectly at the maximum 160,000 revs.

digitech

My Feedback: (10)

patent or not
the are chinese i deal with them for many years
believe me they will sell it no matter what or schould i say no mattah ?
but can you amagine how that wheel will explode at 160k?
this is a full 99% copied wren enginei leave the 1 % since this is the chinese style
i would not even DARE to run this engine up to 160k
and see the wheels come off
i doubt they can get the steel we use since they import it from europe
i would believe the first statement they made
that i will look wicked next to your computer on a test stand
anyway i just looked at there "factory balancer machine"
so i guess i can trow away my 15000 euro,s schenk balancer
god why didnt i think of this?

Gary Jefferson

My Feedback: (167)

I am not sure why you think it is a problem for the chinese to buy steel from the U.S. My wife works for a steel company and right now the chinese are one of their largest customers. They are buying scrap steel in full containers from her company so unless there is some sort of regulation on selling the exotic metals they use for producing the turbines it is probably not an issue.

ajcoholic

My Feedback: (10)

I personally dont think there is anything wrong with competition, and I know Wren, and probably others do not mind another turbine manufacturer on the market. Certain companies have worked hard for many years to develop a great repoir with loyal customers and have proven their product is safe, reliable,etc.. The issue is not what the engine costs but is it up to the quality standards that we as users NEED asolutely to keep this hobby safe.

If the turbine wheels are cast in the proper materials, to the proper standards and tested as they should with proper documentation, that will ease a lot of minds... blatent copying of an existing engine is still not pleasent for the original manufacturer/designer, but I firmly believe that Wren for instance is more concerned with safety than someone undercutting them in price.

The price is very appealing indeed, but untill it is proven that the wheels are up to standard I would be very cautious.

Just my $.02...

AJC

mikedenilin

My Feedback: (67)

Hi Kelly,

Thank you for the link and technical notes on dynamic balancing. The procedures and the cost of a dynamic balancing definitely make me think twice about assembling my own turbine as a hobby. Can't imaging standing next to a running turbine that is not dynamically balanced!

Mike

mikedenilin

My Feedback: (67)

They don't need to spend 15000 EURO on a balancer. They got enough low-cost labor force to spin their turbine wheels manually and achieve a good balance. Well, that is a theorectical assumption that their hands can spin the wheels at 160,000 RPM on that static balancer. Then again, if they have already sent men into space and come back in one piece, why can't they make good turbine engines?
Any testmonials from someone who really ran these engines?
Mike

ajcoholic

My Feedback: (10)

Mike, please note that there are MANY (like hundreds or more) of sucessfull home built turbines, that are balanced by hand without any electronics. Mine for instance, (two of them) with one engine having run up to 160,000 for allmost 13 hours now (my Wren 54 MKII kit I balanced myself and fly regularly) and a home built KJ66 with about 3 hours on it.

There is nothing wrong with a home balanced engine, as long as it is donr properly, and the person doing it understands what to do (where to remove material) and when is it "good enough"...

For more info join the GTBA and read up on it. Thats not to say electronic dynamic balancing is not better (in most cases) but you wouldnt beleive how smooth an engine balanced statically by hand can be. Nothing unsafe about it.


AJC

Kelly W

My Feedback: (2)

I'm in agreement with Andrew on this. There's plenty of proof that a home balanced engine can work and work very well if its done right. However, I think if someone were to manufacture a large number of engines and wanted to maintain a certain level of quality standard, I think a balancing machine is necessary. The Jetstuff balancer seems to be aimed at homebuilt guys or production manufacturers looking for a low-cost solution. There are much more expensive options.

I can't comment on how good it is from first hand results because it doesn't work yet. Not by fault of the product, just no time to work on the shaft mounting system... This is likely going to be a winter project.

Kelly Williams
PST Jets
North American Tech Support

XJet

Just to keep people informed, JoeJet emailed today to advise that my $30 fuel pump will be despatched tomorrow.

That's six days after I ordered and paid for it, so I guess he's not holding stock but indenting against each order received.

I'll let you all know when it arrives and what the quality is like.