How did you measure the deflection while it was being run to know there was .005" deflection.
Were you using cutting oil? .014" per revolution might be too aggressive if you were getting that much deflection. You had a limited selection of cutting tools. It appears you got it done and it fits nicely, which I’m glad to hear. Curious, did you cut it off at the lathe or on a saw?
Using micrometer, after a pass the diameter at the end of shaft was more than the diameter near the chuck (was probably only deflecting half of what I said initially, diameter vs radius)
That doesn’t mean the bar was deflecting it could be run out or other causes. A piece of metal 2X in length of its diameter, especially a piece of hardened steel I doubt could deflect that much without some serious pressure being applied and the noise would have let you know.
Rev 2 has been implemented with a more-powerful horizontal engine, plywood impeller, bent vanes, and - amazingly - no apparent imbalance issues when tested. We made progress on the engine stand and impeller housing as well.
Sorry to be off-topic, but I would love to see pics/specs/info on a homeowner-sized chipper that works; I’ve spent quite a bit on ones that don’t.
I have a ~10 year old example of this model. Chipper is excellent - hogs down up to 2" branches (and anything else you can push into the gullet) with efficiency. Shredding function is less efficient since the hopper doesn’t feed reliably.
Getting close to starting it up, here is a mockup before attaching the base, was aiming for 1/2" clearance on each side but ended up closer to 1/4" clearance
I may have overbuilt it
If I was smart I would have realized when CNCing the initial housing that I would need a hole the size of the impeller to be able to install / uninstall the impeller after the housing is assembled, instead I just jigsawed an 18" circle.
Note the wire mesh safety grate on the intake hole to prevent debris ingestion, the same material will be wrapped around the housing to slightly slow down any shrapnel that leaves at a high velocity (200mph max speed at impeller tip if the motor hits its 3800rpm governor), safety first!
Next time should be able to start it up and try to quantify how much air it can actually move at what pressures.
Was able to test it out, using a water column gauge I estimate about 8" of velocity pressure, with the 33 in^2 outlet area, that should be about 2,500 CFM.
While it was balanced enough to not explode, it was basically hoping off the ground(would slide around if didn’t hold it), so the next step will be constructing a better balancing rig, will need to mill something on lathe as a 3/8 to 3/4 bushing so that I can stick a rod all the way through the impeller to balance with.
Installed new air intake and carb jet, which in theory will give another horsepower
Also greatly improved the balance of the impeller
But when testing and going to full throttle the cast adapter split, other than marring the output shaft keyway a bit it doesn’t looks like it did any damage to motor or housing, but this impeller is trash.
Lesson learned, don’t order random things off amazon even if they are prime eligible, when I ordered it I didn’t realize the split went almost all the way through it, so with the excessive amount of torque being sent through it it gave way.
Will have to start work on the all metal welded impeller next, with a proper wheel hub
If I were to get a bushing again I’d go to Slow Motion industries, really its Motion industries but they are slow as Christmas.
Also I did some more thinking. You need to get the impeller balanced next time. I’ve seen a motor unbalanced crack a 4" solid steel shaft. Take it to a drive shaft shop they might be able to help or an electric motor rebuild shop. We use Brendan & Clark in north Ft Worth for balancing motors, rotors & impeller assembly’s.
Got my pressures backerds. Lol
You guys are crazy with the testing! I worked for almost 3 years as a contractor at Bell Helicopter and have seen blades come apart under testing. They test it in a special rig with huge iron beams hanging from the bottom of chain link fencing that sits up high around the horizontal test plane. When they fly apart pieces can fly incredible distances.
Now granted, you aren’t turning with the same amount of forces that they are but I wouldn’t be surprised to see pieces fly at least 100 feet if that thing comes apart during testing.
Started work on new steel impeller, the main plate is out of 11 gauge sheet of steel (1/8" thick). Will be using a machined not cast wheel hub to connect it to the motor, used bridgeport to cut the 4 1/2" holes on a 4" diameter circle.
To make it a round 18" diameter disc, first roughed it down with bandsaw, then used the rotary table on the bridgeport, after finding center of rotary table using coaxial indicator, then used a 3/8" drill (same size as was drilled in center in above picture) to hold the steel sheet centered on table while tightening it down. The fact that the T nuts don’t fit in the rotary table made it very annoying, ended up using 1/2" bolts and having to hold the bolt head from spinning by jamming scrap material next to it.
Using a giant block of MDF I glued together previously I made a mold to bend the 16 gauge sheet metal vanes that will be welded on, bandsawing the pattern then using the vice as a press worked better than expected
Mocked up ready for welding:
… may your weld beads be generous and sturdy. Especially sturdy.
That setup begs to be tig welded.
Just ran across this. Pretty damn cool that the kid has access the the tooling.
https://www.americasgreatestmakers.com/video/jet-engine-go-kart/
In my continuing effort to learn things the hard way, I now know how to turn a steel plate into a bowl.
I started off ok, with a jig to help align the blades, I tac welded all the vanes on
I should have stopped there, but instead I ran a full bead down each side of all the vanes, thinking that the short alternating welds and clamps would save me, instead at the end when I unclamped it it had bowed up nearly 3/8 of an inch around the circumference
The heat lines between vanes are where I tried welding on the back side to straighten it out, it didn’t seem to help at all. (Obviously I have very little welding skill)
As long as it still fits the housing, and balances, it shouldn’t matter that much.
I’m thinking that the distortion may not be so much that you shrank the impeller side along radial lines, since you have those fairly well strong backed with the blades, but maybe that you shrank the circumference of the disk everywhere the blades are, forcing it to distort. Basically wondering if the fix should have been to hammer or stretch on front side the same area you welded?
Here’s a pretty nice article on the topic.
They say the shrinkage will occur length-wise to the weld, since the molten metal shrinks when cooled, causing contraction.
I’m thinking, if/when doing this again, the way to go about it would be with the vanes done “L” shaped, then spot weld them to the plate. Following up with TIG for strength. Preheating would probably help, but might cause warping on its own. You can read those other tips as well as I; maybe better.
I agree with kbraby, as long as it fits and balances, it probably doesn’t really matter for this project.
The keep from warping I’ve done in the past where I hopscotched around. I’d tack them then do an inch or so at a time not letting the work piece get to hot. I’m by no means a welding expert but it has worked for me to keep the warping down.
