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Author Topic: Hi-Zoot crank for Standard Fox P/L or ABC set?  (Read 2322 times)

Offline Dennis Toth

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Hi-Zoot crank for Standard Fox P/L or ABC set?
« on: August 31, 2021, 04:27:37 PM »
Just a quick question about using the Hi-Zoot crank with either a Standard Fox P/L or ABC set? Seems that since the Hi-Zoot has a higher counter balance then the standard Fox crank so is it better to use the HZ with a steel/iron and use the ABC P/L with the standard Fox crank? Anyone try this?

Best,   DennisT

Offline C.T. Schaefer

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #1 on: September 01, 2021, 05:13:42 AM »
Al Ferraro uses the HZ in his  ABC  Fox speed motor. Works fine!

Offline BillP

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #2 on: September 01, 2021, 07:50:46 AM »
Why would it work better with a steel P/L?
« Last Edit: September 02, 2021, 12:30:16 PM by BillP »
Bill P.

Offline Dennis Toth

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #3 on: September 02, 2021, 07:02:24 AM »
BillP,
I assume you were asking Why would it work better with the steel P/L. My thought when posting the question was, since the Hi-Zoot was developed before the ABC era it was designed to add more counter weight to smooth out the Fox 35 run. With the ABC options that came out from GMA then the Fox factory the original crank ran very smooth. If one used the Hi-Zoot you would now have more counter weight then needed and things would go back to the way the old original crank with steel P/L set ran, just that instead of the having the heavy piston you have the heavy crank.

It seems to work with the ABC and has the advantage of high strength, but maybe more vibration then optimal but  we all handled that with the original setup. Point for discussion is with the lighter AL piston does the original crank hold up better and still give less vibration or is the crank still subject to failure when pushed with higher nitro fuel or load?

Best,   DennisT

Offline Brett Buck

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #4 on: September 02, 2021, 11:30:12 AM »
What would it work better with a steel P/L?

  As noted I think he was considering the added counterweight. But there were other aspects to it - like the Randy crank is *straight*, and *concentric*. I am told by some of the more expert Fox reworkers that that makes a lot more difference in the vibration that the counterweight by itself, compared to the average Fox crank. Not breaking in half running high nitro levels  is just a bonus

     Brett

Offline Allen Eshleman

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #5 on: October 16, 2021, 09:53:23 AM »
So does it cause more or less vibration?  The "high zoot" crank.


Offline Dave Hull

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #6 on: October 17, 2021, 01:41:29 AM »
"It will at least put the vibration rpm way out of the useful range."

Hmmm. Not sure what you are trying to say, here. Since the mass of the piston is not altered (reduced) by the use of maximum Zoot cranks, and for discussion purposes, neither is the mass of the rod, fundamentally the primary and secondary shaking forces retain the same minima. You can improve the static balance of the crank/rod combo, which is what I assume was done to get some Zoot into it. That's certainly to the good.

Without a modal analysis of the crank, it is hard to be sure, but if the single-cylinder primary dynamic imbalance is say, at 150 Hz (corresponding to 9,000 rpm) I'm not sure you are going to see flexible crank modes below 150Hz with the stock crank, and not sure the amplitude of any of these higher modes would be noticeable vibration-wise when it is swamped by the 150Hz. Ditto for the 2x secondary shaking force at 300 Hz. So I can't make sense of the original statement.

Where the Zoot should really pay off is in regard to crank stresses in torsion, which is what kills Fox Stunt cranks at the induction port. Of course, they also fail with annoying regularity across the crank web from fatigue due to bending stress. If the material is higher strength, based on a better alloy and better heat treating, and if it reduces the stress concentrations inherent in low cost machine work that characterized the factory part, then the alternating stresses relative to the total allowables should be much more favorable--and the cranks much less likely to depart in flight or shed important pieces inside the case. Both of these are admirable qualities resulting from Zootness.

At 9,000 rpm, you should be concerned about the fatigue limit (reversed loading in torsion) at say, 2x10^6 cycles, which is only 230 minutes or so of operation. You'd need to know the exact stress ratios (alternating stress and constant stress) for all of the torsion and moment loads to improve the approximation.

You can reduce the alternating stresses on your stock crank by using a lighter prop (wood) and lighter spinner. Reducing the alternating stresses will push the fatigue cycle count to the right, getting maybe 2 or 3 times the operating minutes to failure.

Dave

Offline C.T. Schaefer

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #7 on: October 17, 2021, 05:44:28 AM »
Whew, that's a mouthfull ;D.

Offline Dennis Toth

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #8 on: October 17, 2021, 06:36:41 AM »
So in the best situation with the standard crank, wood prop, light plastic electric spinner at around 144 ish flights (assume 4 min per flight) trouble could occur? I think there are many Fox's out there that are just getting broken-in at that point. Probably many that have many times that number of flights and are OK. Seems as long as you don't push the nitro above 10% ish they hold up pretty good. I would think that with an ABC setup it would be even better provided there is not too much pinch at the top. Does the pinch offset the extra balance of the shaft counter-weight?

Question is for a 4-2-4 run on an ABC setup how much pinch is correct? Or is it better to run the ABC's in a rich2 - 2 - rich2 with a lower pitch but higher rpm?


Best,   DennisT

Offline Dennis Toth

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #9 on: September 11, 2022, 01:37:48 PM »
So the question is if using one of Brian Gardren's FOX35 ABC set-up's does the Hi-Zoot crank need to have some of the counter weight reduced?

Best,   DennisT

Offline Brett Buck

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #10 on: September 11, 2022, 02:25:29 PM »
So the question is if using one of Brian Gardren's FOX35 ABC set-up's does the Hi-Zoot crank need to have some of the counter weight reduced?

  I hate to ask this question, but, you installed this, ran it in an airplane, and it vibrated excessively?  That's very surprising.

          If not, install it, run it in an airplane, see if it vibrates excessively, then decide what if anything to do about it.

     Brett

Offline Al Ferraro

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #11 on: September 11, 2022, 09:29:00 PM »
So the question is if using one of Brian Gardren's FOX35 ABC set-up's does the Hi-Zoot crank need to have some of the counter weight reduced?

Best,   DennisT
No, Fox sold ABC, and ceramic set and use the stock crank. The main reason the Zoot crank doesn’t vibrate is that it is straight. I have a Zoot crank in a Fox 35 Stunt with a Gardner ABC stunt set powering a Nobler, and it runs great, no vibration. I also have a Zoot crank with the Fox ABC set and it also doesn't vibrate. My Fox 35 Stunt Speed engine has a Zoot crank paired up with a Gardner 36X ABC set spinning a 7-3/4 inch prop over 16000 RPM, with a in air speed over 115MPH running smooth as silk. I purchased my cranks from Randy
Al

Offline Christopher Root

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #12 on: September 15, 2022, 01:10:35 PM »
Do replacement Fox 35 ABC piston/liners require 28% 50/50 castor/synthetic oil still, or do they use 22% synthetic oil?

Offline Dan McEntee

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #13 on: September 15, 2022, 02:31:31 PM »
Do replacement Fox 35 ABC piston/liners require 28% 50/50 castor/synthetic oil still, or do they use 22% synthetic oil?

  Not generally for the top end, but the crankshaft bushing and rod ends still heed a healthy supply of oil.  I think anything that you would run in a LA.46 or similar engine would be sufficient.

  Type at you later,
   Dan McEntee
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Offline Dan McEntee

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #14 on: September 15, 2022, 03:27:17 PM »
No, Fox sold ABC, and ceramic set and use the stock crank. The main reason the Zoot crank doesn’t vibrate is that it is straight. I have a Zoot crank in a Fox 35 Stunt with a Gardner ABC stunt set powering a Nobler, and it runs great, no vibration. I also have a Zoot crank with the Fox ABC set and it also doesn't vibrate. My Fox 35 Stunt Speed engine has a Zoot crank paired up with a Gardner 36X ABC set spinning a 7-3/4 inch prop over 16000 RPM, with a in air speed over 115MPH running smooth as silk. I purchased my cranks from Randy
Al

   Dennis brought the subject up again because I asked the same question in another thread on the main forum. I have been going through my stuff, cleaning and trying to organize things a bit and found I have a Smith Hi Zoot crank I had been saving. Well, at my age, no sense in saving it any more, so I'll probably build up a Larry Foster type Fox .35 Stunt. The question then came to me, what piston/cylinder do I use. I spent a good  amount of time searching the Stunthanger forum  for any leads into when Randy came out with his crank, before or after the introduction of  the ABC and plasma/ceramic stuff and would it make a difference to use it on one over the other. I never did find definitive dates, but did come up with this thread and post by Randy where he states he designed
 the crank for "about 5 grams more effective countermass, which is exactly what the Fox.35 needed." Here is the thread;

    https://stunthanger.com/smf/open-forum/follow-up-on-current-fox-35s/msg6733/#msg6733
 
   I'm taking that thread to mean that it was intended for the stock Fox engine. I haven't found anything where he explains how he came up with that amount of weight, maybe he just weighed the two pistons and that is the difference?? But to me 5 grams is a significant amount of weight depending on where it is. I can understand the significance of the quality of the piece as far as accuracy goes, but in all the stuff I have read is that the main thing about the Zoot crank is that it is straight, but no one explains how, where or why the stock Fox crank isn't straight. It has been said that it will work with either one, and I said it's like a shoe, it can go on either foot, but sure fits better on the foot it was intended for.

    This wasn't a question I was going to bother Randy with, and as long as the forum has been around, I'm sure it has come up before. There are endless numbers of threads on the Fox .35 and it took me along time to find the above thread the first time and almost as long to find it the second time. I'm not looking to build a world beater engine or start a flame throwing contest  about Fox .35s, just looking for some simple information. I get along with the Fox. 35 and have since I learned my first lessons about them 30 some odd years ago. I have built up some good Foxes for friends, Sean and myself through the years, so they are no mystery to me, but that doesn't mean I can't learn anything else new about them either. I found all sorts of stuff that I might go back and write down what interests me. Along the lines of vibration, I found a post by some one from down under that said the locals there were drilling two small holes in the side of the stock piston under the baffle, which is the side that faces the bypass port. In extensive running, he said that they saw no adverse wear, as the front and back of the piston is where the heaviest load was. Couldn't find anything more on that, but it is an interesting concept to achieve the same thing, a smoother running engine. If I don't get anything more out of it than a comment from someone that says, "Hey, that engine sounds really nice!" and a Classic or OTS trophy or two, I'm satisfied.

  Type at you later,
    Dan McEntee
AMA 28784
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Offline Al Ferraro

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #15 on: September 15, 2022, 09:46:51 PM »
I found that on a Fox 35 Stunt that vibrated real bad and chewed up the back plate had a bad crank pin. I had used a Fox that was a real Cement mixer so I installed the Zoot crank and the Fox APC piston & liner set and it solved the problem. I also make my own stuffer back plate using a piece of .020 spring steal glued on the stock back plate with JB weld. The Fox stuffer back plate will still get chewed up if the rod comes in contact with it and will destroy the engine. I do not use wood in the bypass. I found out that I lost power when I tried it several times. Instead I replace the Fox spray bar in the Venturi with a .156 PA or ST type and that solved the burp and retained  great  power. It’s my opinion that the stock Fox Venturi, spray bar set up is to large (area) for a slow running engine of that size. I use Power Master GMA 10-22 fuel and a Bolly 10.5x5 prop on my Nobler and Ring Master with good results running a 424 break. Sig RC idle bar or Thunderbolt idle bar plugs is a must.
Al
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« Last Edit: September 16, 2022, 08:43:26 AM by Al Ferraro »

Offline Brian Gardner

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #16 on: September 19, 2022, 04:48:43 PM »
No - the Smith/Nelson crank works perfectly with my ABC sets.

Brian

So the question is if using one of Brian Gardren's FOX35 ABC set-up's does the Hi-Zoot crank need to have some of the counter weight reduced?

Best,   DennisT

Offline Dave Rigotti

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #17 on: September 19, 2022, 04:53:04 PM »
Any plans on making more ABC P/L sets for the Fox 35 Stunt engine?  I'm asking for a friend.

No - the Smith/Nelson crank works perfectly with my ABC sets.

Brian
Dave Rigotti
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Offline Brian Gardner

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Re: Hi-Zoot crank for Standard Fox P/L or ABC set?
« Reply #18 on: September 22, 2022, 05:35:58 PM »
Probably, it depends upon getting enough orders/names on the waiting list. It is likely, but a fair way down the track.

I'm way way behind on projects with ST35, Fox 36CS, ST46, ST V60, SH37, OS Max 35S, OS61RF Hanno engines all in line to be done first.

Brian

Any plans on making more ABC P/L sets for the Fox 35 Stunt engine?  I'm asking for a friend.


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