Dial indicating fan runout on EVO 50

[woodturner]

Hi All,

I've read through DavidH's exceptional break down of dial indicating a fan, however my fan screws onto the engine shaft.

Can you make any adjustments to this or am I at the mercy of the alignment Gods?

I did balance the fan (it's plastic) however wanted to set it up as best I can.

Thanks!!

[BarracudaHockey]

How close is it? I'd be more concerned with the start shaft runout, thats what causes the most shakes in the EVO's (in my experience)

[ShawnK]

You're pretty much SOL with a screw-on fan. That's why I gave mine to a friend with a mill and lathe, and had it converted to a colleted arrangement. Got the runout down to less than .0005 total (less than 1/2 of 1 thou.)

The best you can do with the screw-on fan is just get the start shaft runout in good shape. Use small pieces of aluminum foil to shim the clutch on the hub. With a little effort, you can get the tip of the start shaft under .001 without a lot of hassle. It will make a significant improvement.

[woodturner]

Thansk gents. Kinda what I figured, for now I'll go with a screw on as I want to get it in the air.. May look into collet arrangement later on.

Thanks for the aluminum foil tip!

Any hints for aligning the main shaft bearings or can you not influence this?

Thanks again, happy flyin'

[ShawnK]

Again, not much you can do, except to put the main shaft in all 3 bearing blocks during your initial assembly. Use them to align your frame halves, and start attaching the frames by first inserting the bolts that go into the bearing blocks. Work outward from there.

To the best of my knowledge, Hirobo does not have a colleted fan hub for the Evo in their lineup. The best you could do (I think) is get the SD-G flywheel (part no. 412-191), which is a press fit-type that uses the Woodruf key that comes with your engine. You're relying on Hirobo's tolerances to make sure that you have a true running fan assembly.

I've never used one of those SD-G hubs, so I can't say anything about the quality one way or another. Since I have a friend with a small machine shop, I had them experiment with converting the standard hub into a colleted hub. We may refine the idea a little bit yet, but it looks like my friend may consider making modified Evo 30/50 hubs for sale.

['roboRon]

Buddy, would you care to elaborate the collated setup?

I have a mill and lathe + time to make one at work if it isn't too difficult. I don't know if you would like to give any info. away (pictures, drawings) but if you could i would appreciate it.

[woodturner]

Thanks all.. After initially screwing on the fan it was off by .002, I gave the high side a light tap with plastic screwdriver handle, it actually moved got it down to .0005.

One piece of foil for started shaft alignment I'm just over .0005 there too. Yahoo, what luck..

Thanks gents..

[ShawnK]

Buddy, would you care to elaborate the collated setup?

I have a mill and lathe + time to make one at work if it isn't too difficult. I don't know if you would like to give any info. away (pictures, drawings) but if you could i would appreciate it.

Honestly, I'd tell you what I knew, if I only understood more of it. My friend did all the calculations when it came to programming the mill. All I know was that the collets had a 6 degree taper (had to do some math to come to that), and that we had to open up the hole on top of the hub to be able to get a socket in to tighten the collet (it's larger than the stock prop nut that you'd normally use).

The one downside is that since we opened up the hole, it took more work to make sure that the clutch was centered on the hub. On the stock setup, the hole on the top of the hub mates with the step on the bottom of the clutch, so you know that the clutch is concentric. On mine, you had to tighten the clutch down, check the runout, loosen the clutch and tap it just a hair, tighten again, and check the runout again. Lather, rinse, repeat.

Future versions of the modified hub will have us milling down the height of the hub by 5 or 6 mm, and then machining an adapter plate to make sure that the step on the clutch mates concentrically.

Subsequently, I ain't about to take the hub out now to take a picture! It took too long to get it dialed in the first time! :mrgreen: