scale vrs pump

[Joe Patterson]

I am thinking about pumping my Epoxy onto the scale..............just to be sure.

[macleodm3]

Its understandable. A few bucks is a few bucks... but if its gonna be one of the most used tools over the next several years of my life, well, we'll see. I like the idea of the pump the best, as well as ease of use. None of this will help me get a shop built though. Applied for building permit Friday. Got license agreement from AS&S Saturday. Ordering plans Mon or Tues. Shop is gonna run $3k, complete. My labor. I wish SO MUCH I could spend that $$ on airplane materials. We should've bought a house with a basement or a usable attic, or a garage, or even some more flat yard.

[Jim Sower]

I have used a pump and I love it. I've heard many of the stories of failures, but when you think it through, how many stories would you be hearing (and how would the pump folks stay in business) if the hysterical extrapolations were even remotely accurate.

 

I've also used a scale. I'm doing it now. I'm using 10-year-old Safety-Poxy and Aero-Poxy, each with its own mix ratio - both different from MGS which I'm using on my airplane - to build my work bench and repair the busted furniture that has accumulated since I last mixed flox. My scale is accurate enough, but it is very slow reacting. I pour a little wait and WAIT and the scale finally increments a little, pauses (just long enough for me to start pouring again) and increments some more. I often over-pour one component or the other and have to increase back and forth. Like cutting a little off a table leg to make it quit wobbling.I can't WAIT to get working on the airplane and back to using a pump!

 

Just squeeze and go ...

 

No more calculations ...

No more staring at a readout you can bare;u read through the Saran Wrap ...

No more back-and-forth trying to even out pour errors ...

No more forgetting to select grams instead of ounces

No more ....

[Dave Clifford]

We cap our spouts at the end of the day. We also keep the box hot 24/7. We found that if you cap the spouts, you are less likely to get capulatory drips from the heat and it also prevents the hardener from getting hard around the spout.

[td_howard]

I use both pump and scale.

 

I have a 60/40 mix fast/slow hardener (MGS system) in my pump, and I use that for 90% of my layups so far. But I also have condiment squeeze bottles of resin and hardener (both types) in my hot box, so if I want a layup to cure faster or slower, I use the scale to mix up a batch of expoxy with the appropriate hardener. I have a chart attached to the front door of my hot box showing the required weights for various sized batches of epoxy.

 

I also use the scale to verify the accuracy of the pump at the start of a work session.

 

BTW, you can get fairly cheap digital scales from here:

http://www.stores.ebay.com/digitalscalesdirect

 

A 3KG scale goes for about $30 if you buy it direct, you may be able to get it cheaper via auction.

[cncdoc]

2 things:

 

1. Different epoxies have different ratios for mixing, some are more suited to measure by weight, others by volume.

 

2. If the pump (Sticky stuff) had some sort of CD player or light show or SOMETHING that would make this simple device worth the price ??? $$$. I dunno, it just seems a little high for what it is. I'll have to bite the "bullet" and buy one some day, because after searching the internet for another usable pump, I couldn't find one. I DID find a few sites where guys have made their own pumps from condiment pump from the restaurant industry at a fraction of the cost.

 

But hey, if price were an object, would I even be building an airplane?

 

That's one question you NEVER ask (even rhetorically) the GIB!

 

....back to "pumping" the wallet...

[marbleturtle]

Ranting about price! (skip ahead for more meaninful epoxy pump information...)

 

1. John Smith says the price is right if someone is willing and able to pay it. (I kinda paraphrased that one.)

 

2. I'm in the software business, and the price of the software is usually 30% of the net gain in income created by it's use. (I work for a company that saves hospitals millions of dollars every year... our software is a little expensive despite the fact that its production cost is relatively low, or almost $0 for each new hospital!)

 

3. The price of an item is its cost plus a reasonable profit for the manufacturer, distributor, sales rep, local government, federal government, and the cost of those items that "fall off the truck."

 

Now, since the pump appears to be 2 plastic containers, a metal stand, and a few leaky gaskets... I would prefer to pay Number 3. I expect that would put the pump around $75. However, those involved with the sale of the pump are aware that we will be working thousands of hours on our aircraft. A sticky stuff pump could reasonably save us hundreds of $$$ in productivity. Since this product saves valuable time, and since there is no competition, the price stands at $219.

 

Can you tell my Masters' studies were in Economics?

 

(-- skip to here! --)

I didn't mean to get into all of that... I just wanted to know if the @#$%!@##@!!! thing was gonna spring a leak on my motorcycle! (The only place I have to put the hot box)

[Norm M]

<<Now, since the pump appears to be 2 plastic containers, a metal stand, and a few leaky gaskets... I would prefer to pay Number 3. I expect that would put the pump around $75. However, those involved with the sale of the pump are aware that we will be working thousands of hours on our aircraft. A sticky stuff pump could reasonably save us hundreds of $$$ in productivity. Since this product saves valuable time, and since there is no competition, the price stands at $219.>>

 

The parts listed are the simple pieces. The complicated piece is the piston block assembly, which has a couple check valves associated with it. And there are two of those assemblies (or a block with two sets of machining. Not terribly complicated, but compared to what most people buy from Brock, and what they pay for it, this pump is priced OK. Here is another measure- How many builders who have finished their plane are interested in selling their epoxy pump?

 

Pumps vs Scales will always be a religious matter for some people. It would be good if people could build a bulkhead or similar with a pump, and another one with a scale, and then decide what works for them. The important thing is to focus on building. Planes have been built with pumps, with scales, and with balances.

 

Here are some pump pictures that may be of interest.

 

This is what your hotbox looks like during Chapter 3:

 

http://www.gourmetdamage.com/images_01/PIC00118.jpg

 

This is how you reload it:

 

http://www.gourmetdamage.com/images_01/PIC00153.jpg

 

This is probably how you start to break the containers:

 

http://www.gourmetdamage.com/images_01/PIC00174.jpg

 

You can see how the hotbox gets messier through the build here:

 

http://www.gourmetdamage.com/images_01/PIC00411.jpg

 

I have not had any leaks from my pump, but probably should tear it apart and put new containers on it, just because.

 

Regards-

Norm

[chuckthedog]

I got my Sticky Stuff dispencer in 1983. It still works. No it is not for sale. I have built 2 Long-ez's with it, and a lot of stuff for other people. I sugest that you clean it every 2 or 3 years.

[CBarber]

2 or three years.....kewl, that means I can ignore it for another 6 months to 18 months. <g>

 

Chris

[Joe Patterson]

Of course I am asking this question for a friend,.........

 

If someone was to use the scales method of measuring Epoxy/Hardener, what Increments might he/she want the scale to be able to measure.

 

 

I.........I mean he/she found scales that measure 2 or 5 gram increments. Would that be sufficiently small enough increments.

 

There are also scales that measure in 1 gram increments, but you have to give up Total capability or Versatility, or something.

 

Here is the Link my friend sent me........

http://www.oldwillknott.com/cgi-bin/htmlos.cgi/08178.10.072898374219704492

 

 

My personal pick would be the "Ultra Ship 30", under the Postage & Shipping section.Scale = shipping is $60.40

[dust]

Well joe, on plane day this weekend, i'll take out our scale and measure how much 8 pumps weigh and how much 1 pump weighs and that would be about the range you need, any pumpers out there that can do that for rising spirit before sunday, he is just burning up with a fever to buy this scale, i mean his friend is.

 

hows the "fir" firewall coming?

 

enjoy the build

 

dust

[Joe Patterson]

I do appreciate that dust, but I really was hoping one of the people using scales, would give me their input........

 

I f you look two posts up, ....I need to get some opinion of Scale increments that a person would want their "Scale Only Method" of mixing epoxies to have.

 

Do you think 2 gram increments will suffice?

[dust]

Well, i am just working the problem backwards, if you know the total weight of a small batch, you then know what the individual hardener and resin must weigh, and then the mfg specs will tell you how much you can be off and that will tell you the minimum accuracy needed.

 

enjoy the build

 

 

dust

[Marc Zeitlin]

Originally posted by Joe Patterson

Do you think 2 gram increments will suffice?

Let's assume that the smallest batch of epoxy you'd ever like to mix is on the order of 1 OZ or so - I think that's pretty close to one pump from my pump. Maybe it's smaller, but let's use that for sake of argument. If 1/3 of the volume is hardener, that leaves us with 1/3 OZ of hardener (approximately). 1 OZ = 28.6 gm, so 1/3 OZ ~= 9.5 gm. If the resolution (to say nothing of the accuracy) of your scale is 2 gm, then the best you can do is about 22% error in the measuring of your hardener. If you're 11% off in the measuring of your resin in the other direction (2/3 of the volume), then you're approximately 33% off in the ratio in the worst case in small batches.

 

There's certainly some leeway in mixing epoxy - it doesn't have to be perfect, but 33% off is not something I'd build a plane with. I have a pump - I wouldn't be without it.

[Jim Sower]

Originally posted by Joe Patterson

I.........I mean he/she found scales that measure 2 or 5 gram increments. Would that be sufficiently small enough increments .... Here is the Link my friend sent me........

http://www.oldwillknott.com/cgi-bin/htmlos.cgi/08178.10.072898374219704492.... personal pick would be the "Ultra Ship 30", under the Postage & Shipping section.Scale = shipping is $60.40

Joe,

Marc "did the math" for you. It's crucial. I feel very strongly that 1g or 0.1oz is the minimum acceptabile granularity. I use a 3-kg or 5-kg capacity scale with 1.0g or 0.1 oz granularity. I would NEVER use anything coarser than that.

 

The mixing table I have posted next to my epoxy storage "oven" has 3 columns. It lists epoxy in 10g increments, appropriate hardener amount in 0.1g accuracy and total weight of the mixture in whole grams. I pour epoxy first and then top it off to the corresponding total weight with hardener. I typically start with 50g (small repair) or more often 100g-200g (MAX) in the cup and add enough hardner to get the right total weight. Very occasionally, I use 10 or 20g epoxy and 5 or 9g hardener for small stuff. The longest day I live, I'll not mix more than 500g of epoxy in one cup, much less 4-5kg.

 

Your choice has 14kg capacity (monumental overkill) but 2-5g granularity (totally unacceptable IMO). The two scales that bracket yours on the list (6001T and i5000) are both much better choices IMO.

[Joe Patterson]

Sounds to me like having both the scale and the pump, is the way to go.

 

I thank you guys for the information. I had found some scales with 0.1 gram increments , but thought that was "Overkill".

 

I am just guessing, as I haven't done ANY of this kind of Epoxy Mixing.

 

So 36 ounces would be fine, with 1/10 gram (o.1)increments......

 

I know everyone likes the pump, it just sounds, to me anyway, like BETTER SCIENCE to use measurements.

[dust]

No need to insult all of us pump users, just because you have decided to use a scale.

 

enjoy the build

 

dust

[Jerry Schneider]

Originally posted by Joe Patterson

I know everyone likes the pump, it just sounds, to me anyway, like BETTER SCIENCE to use measurements.

 

Not EVERYONE.

 

I use an Ohaus electronic scale (Ohaus...the name drug dealers trust.), for many reasons.

 

I don't like having to check calibration, leaking reservoirs, replacing O-rings, having to pre-blend hardeners.

 

I like the feeling of accuracy and I get with a scale (real or imagined).

 

I'd rather fight than switch!

 

Just another opinion....

[Rui]

Just got back from Staples where I picked up a 1 gram granularity scale for $42 Canadian. I looked on ebay and the going

price was ~$US20, by adding the ~$US7 - 10 shipping charges it would come in around the same price.

 

I have a pump, and plan to use it most of the time, the scale is only for calibration purposes, but I guess its a good backup in case the pump fails. I'll also look into the check valve that someone on the Cozy list said Micheal Engineering has for people using MGS 285. I hope to avoid leaky pumps....

[Joe Patterson]

I didn't mean to be insulting..........Maybe I said it wrong.

 

I am hard on MYSELF, the statement about "BetterScience",is the criteria I impose on myself, not on others.

 

1.) The pump seems to be for Efficiency.

2.) While the Scale seems to be less efficient, and more controlable.

 

Don't be pickin a fight with me, the day ofter my birthday...unlessen you bought me a really nice gift...............Like a pump or a scale, or some Cozy buildin materials.

[Dan Tomlinson]

I use a Pelouze postage scale (digital - 2 gram resolution) and it is about right. I wouldn't go 5 gram - as the tolerance would be a bit wild.

 

1 oz is 28.375 grams, and I can't remember mixing a batch that small.

 

My normal for MGS 285 (100:40 by weight) would be 50:20 100:40 200:80 and sometimes 400:160 but that large is very rare - 454 grams total is 1 lb, so a large tub.

 

Why the scale? It's fast and easy - each of resin and hardener(s) in a 1 gal bottle with a pump top - measure what you need of each to make the total weight, and mix!

 

Using a matched "measured" metering pump might save 30 seconds or so per batch - but certainly not more. AND if a pump misfires? Just press again until the weight is right - the pump is only a delivery system, not the measurement.

 

Pump or Scale seems to stir plenty of debate - but done like this seems to be close to the best of both worlds!

 

 

 

/dan

 

PS: This scale (5505) has an auto-shutoff which is annoying - pressing gram/oz while powering on and holding until it displays SHOF will defeat that "feature". It's not in the manual!

[td_howard]

Originally posted by Rui

Just got back from Staples where I picked up a 1 gram granularity scale for $42 Canadian.

 

 

Prices must have come down recently - when I did this a couple of months ago, you couldn't get a digital scale for < CDN $60!

 

 

Anyway, just thought I'd mention that so far my pump is working flawlessly on MGS 285. I verify it on the first pump of the session, and it always checks out OK.

 

One thing slightly worrisome is that if it has been sitting for a while, the first pump contains a small discharge of what I assume is the seal lubricant from the hardener tube. When mixed up, the expoxy is clear, and subsequent pumps are clear. The epoxy hardens OK and gives a positive scratch test. I also did a peel test using one of these "cloudy" batches and could find no difference between it and a "clear" batch, so I haven't been too concerned about it. I found a reference to this in the archives, but the poster just mentioned it in passing and basically said what I just did- that he wasn't too concerned about it.

 

Do you think 2 gram increments will suffice?

 

3 pumps MGS 285 is about 63 grams (45g resin, 18 hardener), so 1 pump is 21g (15 resin, 6 hardener).

Your worst case scenario is underweight of resin and overweight of hardener so at 2g resolution, that would be 13g resin, 8 hardener, for an obtained mix ratio of about .6, a 50% deviation from the required mix ratio of .4 for MGS 285. At 1g resolution, the worst case scenario (14g resin, 7g hardener) gives a mix ratio of .5, which is still 25% off. This is still not in my comfort range so when I use the scale, my min. batch size is about 50g.

 

Of course, things get better the more you mix up. At 63g total weight indicated, a 1g error yields a worse case ratio of .43, which is probably OK for our purposes.

 

Having said all this, I only use the scale for special purpose (ie all slow or all fast hardener) batches anyways.

 

Note if you have a scale that goes to up to 3kg or so, you will be able to weigh all your early parts, so you can compare them to the weights posted on Marc's site and elsewhere.

[dust]

I gotta say, when i started this thread i did not realize the religeous impact it would have and love your bother/sister builder wether they weigh oir pump. he he he

 

enjoy the build

 

dust

[Rui]

I did some testing yesterday on my new scale (btw, its a Pelouze too) and found that the advertised 1g accuracy is rather optomistic. I weighted two empty beer cans and each alone weighed 14g. When I put both of them on the scale, however, I got 30g.

 

So I think a safe bet is that the mechanics of this scale are the same as the 2g resolution scale, but the display just tricks you into thinking its more accurate.