Gyro build problem

[Bruce EdneyParticipant @bruceedney59949]

[Bruce EdneyParticipant @bruceedney59949]

Hi folks

Need a little help. I am trying to build a gyro based on plans from Chris from Clickspring. **LINK**

I didn't have the required stock so I scaled it down to 74% of Chris' gyro.

My problem is it won't stand up – it seems top heavy.

I have noticed the I have not taken quite enough material from the pockets on each side of the flywheel. Could there still be too much mass in the flywheel?

Any help appreciated

Bruce

[JasonBModerator @jasonb]

Usually the more mass in the flywheel the more stable the gyro will be once you have the flywheel spinning. All these type of gyros are top heavy until they are spinning.

Have you scaled all the parts the same amount of just the flywheel?

Part 1

Part 2

 

 

 

Edited By JasonB on 10/12/2015 07:51:08

[Bruce EdneyParticipant @bruceedney59949]

Hi Jason

All parts are scaled so far.

I have been spinning it up with air to quite a high speed

Bruce

[JasonBModerator @jasonb]

Same materials?

[Bruce EdneyParticipant @bruceedney59949]

yep

Brass flywheel, ali ring and steel shaft

[Ady1Participant @ady1]

If it's topheavy one way then flipping it 180 degrees and firing it up should make it extra stable, yes/no?

[Ady1Participant @ady1]

If you go to 10 minutes in to video 2 the design seems pretty bulletproof, you do need to get it up to a sufficient speed though

[Peter KroghParticipant @peterkrogh76576]

The mass is best if most of it is in the rim of the wheel. The hub and inner disc don't contribute much.

Pete

[mechman48Participant @mechman48]

I have built this same model …twice, one with a plain inner ring & the other with the holes in… & have had the same exact problem, I thought it was top heavy too so switched them both around 180*… no improvement… there seems to be an out of balance somewhere but can I as heck find it.. I set it off with a 3ft cord so it gets up to some speed but then the ali ring starts to spin with it, which is not s'posed to happen, when the spin eases off it gets top heavy again & then go shooting off the bench… all the materials are the same, & I made sure that all dimensions were exact using DRO's, even ensured the shaft had sharp points & oiled the brass cups with a drop of light oil…I even checked Springsprings video 3 times & I haven't done any thing different to his procedure, I thought it was just me that was having probs… glad to see not, so Bruce where do we go from here … ……?

George.

[Ady1Participant @ady1]

If you look at kiddie gyros which are designed specifically for low speed use they all have a very thin profile

There's probbly a mathematical formula somewhere out there for the optimum mass distribution, speed and momentum, and since speed is the limiting factor on a manual gyro the other factors need to compensate

There's a fat gyro here, precision made, 12,000 rpm…

Edited By Ady1 on 10/12/2015 11:19:33

[duncan webster 1Participant @duncanwebster1]

if you scale the dimensions to 0.74 of original the mass of all the bits reduces to 0.74^3=0.41, but since the the moment of inertia is mass*radius of gyration^2 it reduces to 0.74^5=0.22. It's a very long time since I did the maths for gyroscopes, but reducing the mass of the non rotating bits is an obvious start, and as Peter Krogh says above getting the mass of the flywheel in the rim will probably help as thinning the web will reduce the mass more than the moment of inertia.

A good start would be to spin up the flywheel and axle without the frame. There is some magic ratio between length of axle and inertia of flywheel which must be met or it will topple over. If it won't work without the frame it has no chance with it. Perhaps some mathematically minded reader will take this on as a Christmas brain teaser!

[Brian Boyle 1Participant @brianboyle1]

Made this same Gyro as a present he other week and had the same problem. The performance was only adequate. I used the flywheel to make a finger engine instead.

[jason udallParticipant @jasonudall57142]

Taking Duncan s formula as read.
Mass by 0.74*0.74*.74= 0.41…

MI of rotor.. M *r*r

So thats 0.41*0.74*0.74..= 0.21

so assuming the mi is acting against the torque ( on this case to fall over)…
We have torque T proportional to mass* half height…ie T proportional to 0.74^4
And MI proportional mRR. 0.74^5
This means the restoring “torque”.. seems to reduce by 0.74 relative to the tendancy to fall over…
Thus a design that works at 1:1 might be marginal or not work at 1:0.74

Ants ( bees, and other arthropods)..don’t work scaled up to the size of sheep.

[jason udallParticipant @jasonudall57142]

A possible solution might be to use a flywheel of higher in proportion mass….. ( lead?)

[Martin ConnellyParticipant @martinconnelly55370]

A bicycle wheel makes a good gyro even though it has a low mass rim, it's just a large radius. Perhaps you could try removing material from the inside of the rim so you have a lower overall mass but keep the most effective mass, that is the mass that is as far from the centre as possible. also thin down the centre boss as much as possible, this is mass that is supplying very little gyroscopic effect. Finally drill holes in the outer ring to reduce its weight. It does not need mass or great strength.

Martin

[JimmehParticipant @jimmeh]

I had only just faced up a piece of 2" brass bar ready for turning into the gyro flywheel before coming in doors and reading this thread. I was worried that the gyro may not work with the smaller diameter wheel and had planned to reduce the section of the aluminium ring and steel arbours to the bare minimum. The Flywheel should have a nice thin web with a light boss in the centre and a relatively heavy rim. If I'm successful I'll post back my findings in the next week or two when I've had the chance to build it.

It seems Clickspring has inspired more than a few people with his excellent videos.

Edited By Jimmeh on 10/12/2015 17:46:05

[Bruce EdneyParticipant @bruceedney59949]

Thanks for all your comments.

Some of the maths lost me a bit but…. Phew it is not just me.

I will try taking some mass out of the web and centre of the flywheel and let everyone know how I get on.

Thanks again

Bruce

[Andrew EntwistleParticipant @andrewentwistle]

Hi Bruce,

I made one with very similar dimensions to Chris Clickspring's drawing but with ball bearings so that it could be spun up with a Dremel. Using string I also found that it was 'top heavy', it needs to run above 10,000rpm to stay in a horizontal position https://youtu.be/N6EogFmO-7A. I made another last weeked with my 9 year old nephew with the flywheel 11mm thick, 15mm rim and 2mm web and this one with point and cup bearings works well using string to run it up.

Andrew.

Edited By Andrew Entwistle on 10/12/2015 18:10:18

[Peter KroghParticipant @peterkrogh76576]

Thanks to the discussion, the relationship popped back to mind. IIRC it's something like W.r.r/2 for the inertia. Hard to math on the keyboard! But the inertia is an r squared function as everyone has stated so for a given total gyro weight the larger the rim radius the better the stability.

I love gyros; it's been a long time since I made one. Somehow I feel another coming on!

Pete

[herbert punterParticipant @herbertpunter99795]

Does anyone remember that massive beastie that Professor Eric Laithewaite demonstrated at the Christmas Lecture too many years ago?

[herbert punterParticipant @herbertpunter99795]

Here it is : **LINK**

[mechman48Participant @mechman48]

All comments noted but even looking at Clicksprings video again I have done everything as per his drawings & process yet am still not seeing how his works perfectly yet mine ( ours ) does not . I have now put both my attempts to rest for a while & contemplate doing something else.

George.

[pgk pgkParticipant @pgkpgk17461]

..unless some other phenomenon is at play?

At one job the only way i could get a readable ECG trace was with the patient positioned N-S. Any other direction and the baseline oscillations on the trace made it unreadable. The proximity of ley lines, my boss's antimagnetic personality or the electrified railway at the bottom of the garden were all considered causes..

Where i live now there's a 600ft ridge just across the field. One day i shall find the energy to climb it and recover all those small parts missing from my shed. I'm convinced of the mass attraction that causes them to vanish.

Fast spinning objects may well be communicating with an alternative reality.. why in some places you can put a pair of socks in the spin drier and only ever recover one sock. It's no stretch to consider a perfectly spinning gyroscope can also exhibit abberant behaviour <s>

[Roger HartParticipant @rogerhart88496]

Take a look at http://www.gyroscopes.org and the maths tab. I plugged the 'as spec' numbers for your gyro wheel and chose 5000rpm and then entered the 'as scaled' (with a bit of guestimation). To get the same gyro couple it seems the rpm need to go to about 20000 or more. A bit of a problem with windage and bearing loss. This fits with my experience, I made a smallish gyro and the performance was pretty disappointing. I ended up mounting it in double gimbals as a demo. So, 75mm OD looks about the minimum in brass.

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