Hi all...

Yesterday I test ran my G-62 with a homemade 2:1 belt drive using a 3W 32x12. The performance is quite acceptable as it swings the 32x12 at 4000rpm at full power, but it is the idle I donīt like. As soon as the engine goes below 2000rpm (on the prop, 4000rpm on engine) the whole assembly starts to shake like mad and the engine quits within a few seconds. When using the engine without the belt drive I can get a reliable idle at about 1500rpm.
The engine is hard mounted on aluminum standoffs and does not shake too bad without the belt drive.
The whole drive is built pretty much like the one Mick Reeves sells for the G-62, although the prop shaft is mounted below the cylinder. Like the Reeves unit there is no additional flywheel mounted on the engine and belt tensioning is accomplished by moving the prop shaft up and down using washers.

Do I have to convert the G-62 to electronic ignition to get this to work? Or will a steel flywheel mounted on the engine make a difference? Anyone using a belt drive care to enlighten me?

I have never heard that the people using the Toni Clark 2,8:1 drive for the G-38 have any problems with the idle..... is it just me?

Attached is a drawing of the general layout of the drive.

Heavier flywheel would certainly help where normally the prop is the flywheel. Also marine engines need to run a flywheel for the same reason. You will also get a slower idle speed.

It is best to have a mounting system which absolutely locks front of engine and forward prop shaft into a rigid setup -
There must be NO chance for the engine to have any "wind up " in the drive belt -thru wobble or tension change on impulse.
4000 engine rpm should not be considered "low"
Once you use flywhel and build up to a heavy structure - you get into a very heavy power to weight setup.
We have done these setups -using cog belts (on smaller engines ) and they do work.
the system tho must be rigid tho -
yours looks to have possible "windup ".

I ran one of the Mick Reeves units with my ignition on it, no problem with the idle....

I don't know about prop drives, but most belt drives use an odd ratio to trying to prevent hormonics

That's what we need, no HORMONICS
Fingers working good this morning, TK ?

The weight of the drive is not important as it will eventually be mounted on a 1:5 scale Hawker Typhoon.... I guess I will need the noseweight anyway...
This is only the first prototype. The final version will have a 3:1 ratio.... or there about. Does it matter if the ratio is 2:1 or 2,3:1 in regard to vibrations?
BTW. Today I tested the static thrust with a spring scale.... very disapointing as it was only about 1kg more than a MenzS 26x8 direct drive. About 13kg (29lb)
I also found out that I had a little runout in the prophub that may cause the vibrations.... Iīm going to make a new one tonight. Thanks for your replys so far.

AZDZ80 on a 26x12 MenzS-- Ionce checked with a spring scale -- this was 35 lbs at 6200 rpm.
Iwould -on a Hawker- put my time and money into a good internal tuned can and cooling ducts -and run a good flying prop -instead of going for a big dia prop
Actually you could use a 28x8 and that should haul your bird -Iguess it will be about 30 lbs or so ???--
You will gain static thrust with low pitch setups - get a big ol paddle blade -or make one .

ratios and vibes - yes ratios do change vibes - we spent a couple of years screwing around with twin engines on belts - single gear drives and wild ratios and high tuned engines .
Finally threw in the towel - the harmonics went wild -at some setups -also the props which could be turned -werealways too flimsy and they wuld be seen to waver at certain speeds -.
-- never again--

OK RC, it was late.
2:1 or 3:1 are just about as bad. 2.35:1, 3.35:1 or some odd setting is beter.
The belt drive needs to slowly "walk" around the gears and not have the same spot match up every 2 or 3 turns.
If you have to run even ratios do it with an odd tooth gear and an even toothed gear. Don't use two gears with even teeth counts

that is called a "hunting tooth" setup - and I used it on OS.61 setups (factory) in the early 1980's.
On a tuned pipe -with the "2.91-1 " whatever it was -and a big dose of nitro -this setup really smoked --the noise tho was simply awful .
We flew -at the time - big scale pattern ships which really worked but the "pattern" crowd , simply hated it.
It looked scale and sounded like an air raid siren with a wild undulating pitch.

Hi again...

It seems that that I have completely accurate when I described the belt drive.... It does not use a toothed belt, rather a 20mm wide belt with 8 little "vee-belts".... sorry if I was not explaining it too well. BTW it looks like it is the same type of belt that Mick Reeves uses on his reduction unit.
I will try it today with the new prop adapter I made last night, it looks to be a little more straigth than the old one.
There are two reasons for going this route rather than just using a bigger engine, one is the sound of the beltdrive....(sounds soooo cool), and the other reason is the possibility to drive a scale size prop... Show me an engine who will swing a 33in 3 or 4-blade prop, and still not overpower a 35lb warbird...

Poly V belt - well good luck -
as for the scale flying prop - again - good luck -
these big props -will generate good static thrust -but keeping the thrust going as speed builds is another thing
To explain-- large low pitch props typically will generate only very low airspeeds
your warbird has a very good chance of needing a fair amout of speed to generate good lift.
The combo can be a problem.
for thirty five pounds I would want an engine capable of more than a G62 can muster
Godspeed ---

It can be done..I have a 10 foot Noorduyn Norseman seaplane, about 40 lbs..Flies with a G62 using a 24-8 Zinger prop..Loooong takeoff run off the water, but flies "scale" once in the air....Flies pretty good as a land plane with wheels, with a Zinger 22-10..Loops, rolls, stall turns, things a Norseman probably never does in real life...

Not exactly Hawker Typhoon performance-------------
I would suspect your wing loading is a wee bit less than the Hawker will be --

I was hoping that the use of much larger pitch props would still give me the speed I need. A 23in pitch @ 2600rpm would be about the same as an 8in pitch spinning at 7800rpm.....I guess... But then again the byron Mustang can be flown with a Q-42 with a, Iīm told, lousy 4-blade flattening prop.....
As Iīve always been told, there is no way of knowing if i will work if you donīt try it I think itīs worth a try.

BTW. The prop I plan on using if I can get the drive to work will be a 33x23in 3-blader. According to my informations/calculations the engine will be able to swing it at about 2600rpm.

you are on the right track on the pitch info -now see if the engine will turn that prop at least that hard - remember that efficiency on props is pretty poor compared with full scale stuff-

Hi Rcign 1: You mention 10' Noorduyn Norseman in this column. I've always wanted to build a model of this plane about the size of you'rs. Did you build it from a kit or plans? I'd like to find the plans, can you give me the address where you you got them. I want to build one because in my younger years my grandfather had one for his business and I spent several years working/flying it-hauling fish and other supplies to the camp. I've been thinking for several years now of building one painted up to match his. It was on floats as well. Thanks.

Don / Maac # 7765

Mine was scratch built by a good friend about 15 years ago It's been a great airplane, I did the test flight when it was new and on wheels...Throttle servo went out, had to fly around until it ran out of fuel..Tried loops, rolls, etc trying to kill the engine, my first G62 conversion..It flew around for about 20 minutes, wouldn't die...He might still have plans, I can call him tomorrow..It made the cover of High Flight and RC Report the same month, years ago...Re powered it with a Zenoah twin this year, takes off way quicker....