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 Post subject: Dodo scales for dummies...
 Posted: Mon Jan 05, 2015 10:02 pm Post Number: #1 Post
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Just for clarification, the dummy is me.

I'm doing some experimenting with drilling and layouts at home, and naturally I'd like to be sure that my equipment meets the USBC static weight requirements. Local pro shop has been none too helpful in this regard, so I've been trying to find a used dodo scale. The AMFs show up on eBay, but the prices seem high and I'm always outbid.

Attachment:
20150104_171829.jpg


So, I had some time in the shop yesterday and wondered if I couldn't put something together with some scrap phenolic ply, 8020 extrusion and ball bearings (for fulcrum).

Attachment:
20150104_171907.jpg


It seems to work as expected. I can balance a ball, then change the orientation and it will lose balance (it seems to be sensitive to 1/20th of an ounce).
I can then add small counterweights and get it back into balance.

Now, I need to fix the weight positions and calibrate it so I know when it's within 1 oz and 3 oz. I will add some adjustable (sliding) weights to the rail and mark the positions.

Am I missing something painfully obvious here?

The commercial scales are well designed and made, but this is not rocket science - right?
I'm not looking to accurately measure the total weight, just to make sure my offsets are within range.

Thanks!

Steve


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 Post subject: Re: Dodo scales for dummies...
 Posted: Mon Jan 05, 2015 11:33 pm Post Number: #2 Post
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What you have looks very close.

Positioning the weights on the right side is going to be a task.

I don't know what your budget is but have you seen
http://www.shop.jayhawkbowling.com/Holtzman-Ball-Balance-Scale-15-6100.htm

$450 is a lot less expensive that you'll find for most of the dodo scales.


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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 12:12 am Post Number: #3 Post
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From the pictures you've done a great job. The dodo scale is not actually for weight but is a comparator.

All you need now is some small weights, 1,2 and 3 oz. To calibrate it simply place one weight the 3 oz on the centre of the ball in the ring, balance with the large weights and put the 1 & 2 on top of each other, on the slide and mark the positions, take the 1 off and move the 2 away from the ring end until it balances and you have found the 1 oz mark.
It's linear so you should be able to mark from 0 to 3 oz easily.

If your scale can measure to 1/20 of an oz you will have a very accurate piece of kit....as good as if not better than the Kaufman scales.

Could be a great business opportunity!!!

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 12:17 am Post Number: #4 Post
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MWhite wrote:
What you have looks very close.

Positioning the weights on the right side is going to be a task.

I don't know what your budget is but have you seen
http://www.shop.jayhawkbowling.com/Holtzman-Ball-Balance-Scale-15-6100.htm

$450 is a lot less expensive that you'll find for most of the dodo scales.


That is a really cool scale. Definitely affordable for someone either needing a cheaper option to replace something or someone who is just starting out.

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 12:44 am Post Number: #5 Post
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Thanks for the feedback and calibration advice. I needed some confirmation before I spent any more time on it.

I'm going to turn some brass weights and I'll dial in a couple of 1 oz, 2 oz, 3 oz. I might also make 1 lb, 3 lb, and 5 lbs for the counterweight at the 2x position.
I have lots of scrap aluminum, but the density of the brass makes for a more compact weight.

I couldn't decide whether to sit them on top of the bar, or hang them from below, but on top should work out fine.

I really like the idea for the Holtzman, but it was out of my budget. Given that it was a new design and patent pending, I wanted to DIY the tried and true dodo.

If there was enough interest I could probably put together some kits, but I'm not looking for a side business. I barely have time to bowl! :lol:
Let's see how the refinements work out and see how it goes. I'd be happy to provide the CAD files when the bugs are worked out.

Steve

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 7:15 am Post Number: #6 Post
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I'm not sure putting the weight on the ball is correct, as the weight moves from the inside to the outside of the balance as you weigh a ball. I would calibrate it using a NIB ball with a known top weight. Zeroing the balance with the top weight centred then turning it out 90* should result in a weight change of half the top weight. Alternatively you could move a 1 oz weight from the outside to the inside of the ring.

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 8:51 am Post Number: #7 Post
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LabRat wrote:
I'm not sure putting the weight on the ball is correct, as the weight moves from the inside to the outside of the balance as you weigh a ball. I would calibrate it using a NIB ball with a known top weight. Zeroing the balance with the top weight centred then turning it out 90* should result in a weight change of half the top weight. Alternatively you could move a 1 oz weight from the outside to the inside of the ring.


You are missing the point. This is a comparator and the 3 oz centred on the ball simply makes sure that it does not fall off. The important part is to balance it with the two other weights (2+1) first, then balance it again with only the 2 oz weight further away on the beam. The different points give you the starting point to marking the beam. The one oz weight could then be used further up the beam to give one more mark just to ensure the distances and weights were linear.

The last piece of advice would be to use two clear plastic rulers and glue them to the beam with a space between them so that the 1 oz weight could slide in the space, back and forth between the marks.

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 2:02 pm Post Number: #8 Post
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kart300 wrote:
LabRat wrote:
I'm not sure putting the weight on the ball is correct, as the weight moves from the inside to the outside of the balance as you weigh a ball. I would calibrate it using a NIB ball with a known top weight. Zeroing the balance with the top weight centred then turning it out 90* should result in a weight change of half the top weight. Alternatively you could move a 1 oz weight from the outside to the inside of the ring.


You are missing the point. This is a comparator and the 3 oz centred on the ball simply makes sure that it does not fall off. The important part is to balance it with the two other weights (2+1) first, then balance it again with only the 2 oz weight further away on the beam. The different points give you the starting point to marking the beam. The one oz weight could then be used further up the beam to give one more mark just to ensure the distances and weights were linear.


This is exactly what I was trying to wrap my head around.
When you calibrate the adjustable (sliding) weight on the beam side, are there any assumptions about where the center of mass is on the ball side?

When you turn an asymmetrically weighted ball 90 degrees, the CM will shift one way or the other.
Where that CM falls will be different on every ball, so my thinking was that the beam (counterweight) would have to be calibrated using a known weight difference centered in the middle of the ball.

Otherwise, a 1 oz difference near the cover seems like it would have a greater effect than a 1 oz difference near the core.
Given that it's averaged across the hemisphere and we're talking small amounts, perhaps it's not that critical?

Steve

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 3:23 pm Post Number: #9 Post
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stevespo wrote:
Otherwise, a 1 oz difference near the cover seems like it would have a greater effect than a 1 oz difference near the core.
Given that it's averaged across the hemisphere and we're talking small amounts, perhaps it's not that critical?


How the weight is distributed is pretty critical.

As you'd expect, a 1 oz weight on the left edge requires proportionally more offset on the beam for it to balance.
I calibrated the beam in 1 oz increments, with the weights on the midpoint/centerline of the bowling ball.

Then I moved 1 oz to the outer edge, and it then balanced at about the 1.6 oz mark on my beam.
The distance from the weight to the fulcrum changed from 6.5" to (roughly) 10.75" and 10.75/6.5 = 1.65 so the ratios appear correct (eyeballing it).

Attachment:
20150106_100813.jpg


Steve


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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 7:30 pm Post Number: #10 Post
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JayHawk has a chart where it shows the difference between hanging a counter balance at the edge of the ball v.s. the Kaufman. The Kaufman is off by about 1/4 of an oz for every 1 oz of wt. hanging on the edge of the ball (weighed at the edge of the ball, 2 1/4 oz is close to 3 oz on the Kaufman) with the center of the ball as the balance point. I would be curious if the new Holtzman is comparable to the Kaufman or to the old JayHawk?
Have you seen this thread?: viewtopic.php?t=6474
(see #24 for the chart from JayHawk)


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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue Jan 06, 2015 7:53 pm Post Number: #11 Post
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Yes, I've seen that thread and your wooden prototype inspired me to give it a try. :)
Sure wish I could find a used Jayhawk, AMF, etc for under $250, how did you manage $25? Great deal!

Thanks,

Steve

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 Post subject: Re: Dodo scales for dummies...
 Posted: Mon Jan 12, 2015 2:21 pm Post Number: #12 Post
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Very cool scale thread. Scales are so expensive because they are industry specific and the market is small. Same for the determinator, oil extraction devices and many other tools used for bowling. In many cases it is items that are re purposed and the prices raised for profit.

After seeing the digital scale that is available I started playing around with using two digital scales and a plank board between the two with the ball sitting in the middle. Only had a about a week with the two scales I was trying. I may attempt again when I know I am going to have more time to try and work it out.

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 Post subject: Re: Dodo scales for dummies...
 Posted: Mon Jan 12, 2015 4:07 pm Post Number: #13 Post
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Yeah, I hope we can collectively brainstorm and come up with options for the hobbyist driller. I'm happy to support our great vendors, but can't justify $500-1000+ for something that gets used a handful of times a year. I also can't wait months until I manage to win something on eBay, either. It puts us in an awkward spot.

Anyway, I balanced my new Exile over the weekend and (I think) it worked out very nicely. I was near the limit for side weight and just over for finger weight, which I knew based on the high CG location. Top/bottom was fine. I removed about .3 oz by drilling the ring finger 1/2 inch deeper and that brought both into the 1 oz compliance.

I will verify with my pro shop but I am pretty confident it's all working as it should be.

Steve

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue May 17, 2016 3:10 am Post Number: #14 Post
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Wow. Over the past 6 months I built my own bowling ball drill press and jig, and can drill balls with hole pitches to within 1/16 of inch accuracy, but the scale is that I don't have. I'll definitely try making one of these now that I found this post. Anyone have any updates - or I'll just follow the pictures and discussion.


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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue May 17, 2016 3:24 am Post Number: #15 Post
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That is as far as I took it. I was eventually able to borrow a Kaufman, and finally purchased a Holtzman (digital). Although the Kaufman has a certain mechanical appeal and was fun to use, the Holtzman is far faster and easier (and it takes up a lot less shelf space). That's one purchase I'm very happy with.

If you're interested in my prototype, I could box up the parts and send them your way. You'd at least have something to start with and play around. You'd have to calibrate with some weights, but it's plenty accurate when you get the hang of it. Send me a PM.

Steve

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 Post subject: Re: Dodo scales for dummies...
 Posted: Tue May 17, 2016 9:56 pm Post Number: #16 Post
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stevespo wrote:
That is as far as I took it. I was eventually able to borrow a Kaufman, and finally purchased a Holtzman (digital). Although the Kaufman has a certain mechanical appeal and was fun to use, the Holtzman is far faster and easier (and it takes up a lot less shelf space). That's one purchase I'm very happy with.

If you're interested in my prototype, I could box up the parts and send them your way. You'd at least have something to start with and play around. You'd have to calibrate with some weights, but it's plenty accurate when you get the hang of it. Send me a PM.

Steve


I tried to build a holtzman style scale out of wood. You can buy the exact scale they use online for about $30. I could never get it to weigh the same twice though. I think the wood flexing didn't help and the pivot point wasn't the best. I just gave up on it. If you had some good material, I think it could be done pretty easily. Calibrating might be a little tricky though.

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 Post subject: Re: Dodo scales for dummies...
 Posted: Thu May 19, 2016 12:49 pm Post Number: #17 Post
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I bought the KMT dodo scale that comes with a ball jig. $320 to my door. Drilled 2 balls, weighed them (about .6 of finger and .5 of side). Took them to RENO last week. I watched the guy weight them, same result. They passed inspection. Best bang for buck in my opinion.

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 Post subject: Re: Dodo scales for dummies...
 Posted: Thu May 19, 2016 3:39 pm Post Number: #18 Post
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If you want to see DIY scales, look at herculino's. That's how you do DIY!

Check out the things he made here:
http://forum.bowlingchat.net/viewtopic.php?f=7&t=7618

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 Post subject: Re: Dodo scales for dummies...
 Posted: Sun Apr 22, 2018 9:12 pm Post Number: #19 Post
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Hi everyone,
I am new to this forum and I am trying to find a topic that is most related to my question so probably this is the right one.
I am planning a balance scale with which you can use one of those kitchen digital scales.
The prototype I made works very well with a digital scale bought in a Chinese shop for few euros.
But in order to match the Kaufman scale I need to know how the Kaufman is calibrated.
So does anyone know how it is calibrated?
Thanks guys.
Remo


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