Gearbox Modification.

[gidge348]

Hello all,

Now with a new found enthusiasm for the electrical system on Nimbus, I though I would tackle the charging system and see if I could get that to work.

I have a NOS aircraft regulator that I have been told is 28V but has no markings. The only problem it the connections are just marked 1-4.



I ***assume***?? the 4 connections would be:
Gen HT(+)
Ammeter (or light?) to Bat(+)
Field
Battery(-)

Of course I have no idea if that is correct and also which would correspond to which numbers?

Is there anyone out there that may be able assist........

[cursorkeys]

Do you have any idea what aircraft it came off, you might be able to get a wiring diagram for the airframe?

Does it have an access panel on the bottom? If you can write out the circuit diagram it should be possible to work out the pinout. Most of the old regulators I've seen worked on a 'carbon pile' that controlled the field current which is possibly the big cylinder on top.

If you want to make a regulator instead then this simple circuit works great:

ludens.cl/Electron/dynareg/dynareg.htm

It will need a few small changes for Nimbus use (regulated 12V supply for the logic, regulated voltage adjusted to 28V and a high-side FET and drive as the field is common to B- not B+ on the Nimbus starter-genny).

[gidge348]

Thanks Jon,

I will go through that article and see if I feel confident enough to tackle it

Sorry I do not know what type of aircraft it came from but was told it was 28V 1960's era British military aircraft.

It does have a plate on the bottom and the drum on top comes off, take some pics & go through it and see if I can work out which pin goes where.

I have found a guy on ebay that has some manuals on old aircraft electrical www.ebay.co.uk/itm/RAF-AP4343-Historic-Aviation-Electrical-Manuals-on-CdRom-/131306480875?ssPageName=ADME:L:OC:AU:3160
So have bought this and will have a look through that as well???

Cheers Again...... I think I owe you several beers if you are ever in Australia...

[ozbooster]

Good thing i looked in a few days ago before sending the starter
good info guys , time to look at my starter wiring setup too, although i had it turning ok it was not as lively as in your video Ian

[gidge348]

Sept 30, 2014 16:09:32 GMT -5 ozbooster said:

Good thing i looked in a few days ago before sending the starter
good info guys , time to look at my starter wiring setup too, although i had it turning ok it was not as lively as in your video Ian

Sorry Greg, I thought I had sent you a message about getting it going... I was kind of like a pup with 2 tails after getting it going after so long.....

Jon,
With the voltage regulator I have seen another exactly the same on eBay www.ebay.co.uk/itm/RAF-RN-Aircraft-Voltage-Regulator-Type-22A-Ref-5UC-5797-Hawker-Hunter-etc-/131094981558?pt=UK_CPV_Aviation_SM&hash=item1e85deabb6
The seller lists it as for a Hawker Hunter etc so attached likely to a RR Avon Engine. These seem to have a lot of different types of starters, Air, Cartridge, Stater/Generators & plain starter.

I have pulled it apart and yes it is a "carbon pile" regulator but I have never had anything to do with these. I will draw up a wiring diagram of the unit and may give you some idea it useable or not.

I think I will have to read the link you posted about the a few more times about making my own regulator as electricity is Satan's work and all I can think of is all the magic smoke escaping.....

Cheers Ian...

[gidge348]

Have not posted for a couple of months, but have been busy with the chassis and aero work for the land speed car and did not think that would be of much interest to people here. But boy that aero stuff is confusing and seems to work counter intuitively a lot of the time.

Today I got the drive axel and hubs back from my friends work shop, looks like engineering porn to me....



One thing I have done on the engine is to make a remote starter adapter if the nimbus one dies out at the salt lake. I was intending to use a chainsaw to spin it over, but I am not sure if is will have the cojones to spin it over fast enough?

The other option is to get a winch motor as suggested by Ernie to Anders and run it off 12v and be done with it.

First thing I did was make up the adapter plate. The shaft on the starter was 22mm dia with 20 spline that just happens to be the same as a gearbox input shaft for a Mazda 323 and a lot of other small cars. The spline needed to be cut a little deeper but the shaft was hardened so I ended up using an angel grinder in the tool post of my lathe to get it down to size. A bit rough I know, but should do the job



Then assembled it with a hi-tec plastic bush recommended by my machinist mate www.igus.eu/iPro/iPro_02_0001_0000_GBen.htm?c=gb&l=en



Then to the engine




Fits fine



Now just need to work out what to drive it with.

Cheers
Ian...

[Johansson]

Dec 9, 2014 2:52:24 GMT -5 gidge348 said:

Have not posted for a couple of months, but have been busy with the chassis and aero work for the land speed car and did not think that would be of much interest to people here.

Are you kidding? Bring it on!!!

[gidge348]

I did a test run with the engine yesterday and asked a friend to come up and give me a hand running the Tiernay starter while I ran the engine and did a few tests. The main things I was looking for was all the oil leaks fixed, testing new thermocouples, ungoverned output shaft speed at idle and noise DB's just for the hell of it.

When my friend told some of his friends that we were starting the engine, every man and his dog turned up so had plenty of hands to run things.

Results:
1xoil leak still dripping on the revised gearbox to be fixed
Thermocouples worked fine but one of my eBay aero gauges didn't
Laser tacho would not pick up output shaft speed.
and a very reasonable 135db's of beautiful turbine noise.....

Ok Anders..... the Aero.

I have been dealing with a very smart man in the US called David Woodruff (Woody) www.designdreams.biz/index.html he consults on fluid dynamics but loves land speed racing and cars in general and has put in a huge amount of work into the drawings but like I said it is REALY confusing. Everything is one compromise after another and seems to be a matter of finding the "least bad" option as nothing is perfect. There were though a few areas that revealed some counterintuitive things.

Firstly we started out with a generic shape with an oversized inlet duct in the nose to test drag from the duct.



Then tested flow and drag caused by the duct.



But the weird thing was that the largest drag on the whole car was not the inlet duct or the flow around or over the body but the wake from the small section of front tyre poking through the bottom of the body. As a matter of fact, this drag alone would stop the car reaching it's max speed in the 5 mile available



So the next thing is to look at some type of fairing behind the front wheels among a lot of other things. The problems arise with the chassis etc to re-arrange/re-design things when the aero demands changes.

As I said it is all one big compromise to try and find the least bad solution.

Cheers
Ian...

[racket]

Hi Ian

So its the "suction" from the low pressure areas behind the wheels that are trying to pull the wheels and subsequently the chassis rearwards , makes sense , if the machine wasn't moving and the same force/suction was in place , it'd go backwards at a great rate of knots ................so not only the force on the front of the machine but the negative force on the back of bits that are the big power suckers..............remove those "suckers" and we go faster :-)

The backside is as important as the front side ..............interesting stuff.

What , only 135 db , you're too kind to the neighbours ;-)

Cheers
John

[gidge348]

Hi John,

Not sure of the complete reasoning behind the big drag number, we just discuss that it does not work and go onto something else. So far David has run over 100 simulations so it's just a case of oh well that was pretty bad lets try something else and run another sim.

I think the main problem is that the drag is close to the stationary ground while the floor is moving and induces sheer drag.

I guess its like 2 sheets of glass on to of each other blow a little air in the middle and the slide easily, put a drop of water in there and it sticks like glue. If that turbulence could be moved away from the car and allowed to spread out it wouldn't be such a problem.

Don't worry it was only the Nimbus at 135db still had the Tiernay screaming in the back ground so the neighbours were..... impressed???

Cheers
Ian...

[turbochris]

i wouldn't worry about the starter, i have hundreds of starts on mine. I have a carbon pile regulator hooked to the field windings and I just leave the starter on and let it charge the batteries.

[gidge348]

Dec 13, 2014 14:08:07 GMT -5 turbochris said:

i wouldn't worry about the starter, i have hundreds of starts on mine. I have a carbon pile regulator hooked to the field windings and I just leave the starter on and let it charge the batteries.

Thanks Chris, I guess it was just really a back up if the Nimbus starter dies at the lake, it's a long way to go to have starter problems.

I was wondering if your carbon pile regulator looks like the one I posted earlier?

Do you have any pics?

Also I would be interested in how yours is wired?

Cheers
Ian...

[gidge348]

Hi All, still working on the LSR car at the moment and hope someone out there may be able to help with a technical question about flow rates of the Nimbus Engine.
I have these 2 things here.




And received this question from the fellow working on the aero for the car.

"The other thing I have been pondering are the velocities on the working cycle and air flow diagram. When I run a simulation of the Nimbus the CFM numbers are very high with these velocities. Me thinks these are peak velocities and not average. Near as I can tell average would be about 80% which compares well with the Nimbus CFD."

I guess my question would be, do you think the diagram would relate to the "flight idle" state of the engine or the "100%" state of the engine?

Or have I got the wrong end of the stick?

Cheers
Ian...

[racket]

Hi Ian

Yep , those are full throttle numbers , 600 ft/sec at the compressor face will have static air pressure down at ~12 psi , the other ~2.6psi is the dynamic component of the 14.6psi total pressure on the diagram , the axial comp wheel will have ~0.25 square feet of inlet.

Cheers
John

[gidge348]

Thanks John, much appreciated.

Cheers
Ian...