Discussion and questions related to the course Practical Engine Building
Hi guys just looking for a rod balancing tool at the moment i am looking at a proform item
Was wondering if there is one that you giys have used/preferred. All that i have seen seem vary much the same to look at. But i would think to use there could be some differences for repeatabilty ect ect.
Same question with scales to balance the rods i cant seem to find anything that is not worth sort of $300+ that will read to .00 i am a little sceptical about buying cheap scales off ebay for the fear of them not being vary good quality.
Any input is much appreciated
The balancing fixture we use is from Jegs. It's just a generic fixture and was about $100 usd. There are undoubtedly better fixtures on the market and ours does require a little finesse and care in order to get repeatable results. I actually started with a set of $300 usd scales from Jegs and found them to be junk. Believe it or not I'm now using a set of $20 usd digital scales from aliexpress. Despite my severe reservations over the price, I've found them to be accurate and repeatable. Make sure you get a set that will handle up to 2000 grams though as you'll need this range when weighing conrods with the fixture also on the scales.When we're balancing engine components, the absolute value isn't anywhere near as important as the repeatability of the scales (the ability to weigh the same part 5 times and get the same exact result).
Here's a similar example to what we're using - https://www.google.co.nz/search?q=2000+gram+digital+scales+aliexpress&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjFhMr_robcAhUMpZQKHXoxBsAQ_AUICygC&biw=1920&bih=983#imgrc=G6LPWRSSTHGNGM:
I had a go at balancing my rods last week, using the exact same balancing fixture as Andre has in the video series, and a near identicle set of Ebay scales. And it does work, but damn is it hard to get consistent results.
The scales themselves are very good. They consistently measure the same value over and over. Although, i measured a few grams higher wieght than the wieght the con-rod manufacturer (Manley) stated for each rod. But the scales were consistent in there own repeatability each time, which i guess is the more important thing to get right when it comes to this.
The fixture on the other hand, not so good. Extreme care must be used when putting the rod into the fixture. Just the way you place the rod on it, will alter the results. So you really need to concentrate with the way in which you place it, so that you do so the same for each rod.
The biggest issue i found is any slight bump to the fixture will change the readings. So if you are half way through your set of 4/6/8 rods when you accidentally bump the cradle, you need to go back and start again, as the results you measure after you bump the fixture will be different to the results you got prior. No matter how perfectly you re-posistion everything, the results wouldnt be exactly repeatable.
Once you have the knack of placing the rod on the fixture, and can do so without disturbing the fixture in any way, then you can start to get repeatable measurements.
I think you will still need to take a few readings and average them out. I found once i was consistently placing the rods onto the fixture, the results were always pretty consistent. But did vary a small ways. If i was unfortunate enough to bump the cradle, then Id basically need to scrap all my previous measurements and start over for all of the rods in my set.
Hey mate i spoke to a local shop and they said that that style is vary fussy so i ended up ordering a chain type fixture. To try help me out abit. I have ordered and received this one.
I am just finishing up making a arbor for the big end atm so i can give it ago. The fixture itself is beautifully made i must say really nice in the flesh.
Thanx for the detailed reply mate.
Just finished this so thought that I'd chime in.
For the scales, I used some similar to the scales used in the videos. I first bought this brand and it was dead on and repeatable. I used it to weight my pistons.
I had to buy a second scale to weigh my rods once I realized that my original scale only read to 500G. Overall it was pretty good, but the measurements did change between different days when I weighed the rods. I also bought a set of cheap calibration weights. With the big end of the rod/fixture on the scale I added weight and there was variation depending on where on the scale that the weight was placed. However, I tried to weigh all the rods and grind in one session in the hopes that it would be more consistent. I think it's also a good idea to measure and mark the fixture with a sharpie so that you can line up the scale so that the rod is in the same position, direction and height each time.