I decided I should get off my lazy fat butt and get to building my engine. It is going to be an .061 bushed to meet the pylon rules here.
I started and almost finished the crank today. This is the rough form, everything is a bit oversize so I can polish and fit after heat treat and grind.
Some details, The journal is .3125 dia with the passage bore at .228, the pin is .137 dia. the counter balance is way thicker than the std Norvel crank and the over all length is shorter than the Norvel. Timing on the widow is 36 deg after BDC and 64deg after TDC the window is .375 long, The edges of the window were left with a .015 flat as per common practice on high reving speed engines (not sharp)
the crank on the right is a Norvel crank for comparison.

Sounds like an interesting project, do you have any drawings of what the finished product will look like?

Chris

Cool. As to your comment on the .015 flat as per common practice - I have seen and read this both ways, as you describe and also with great pain taken to "sharpen" the edge. I am not sure any more which is the better way.

Any idea what the AP crank is made of? Good quality steel? Hardened? Would it respond to being hardened and tempered? I know the Norvel cranks are pretty tough. I usually temper Cox cranks before I build an engine but I was wondering if the Norvel cranks would be better off if they too where tempered in the same way.

Do keep us updated, I find this very interesting but then I do like to tinker with the engines (sometimes good and sometimes not so good)

I have an AP 061 and a pre revlite Norvel AME 061 and dug up some Norvel 049/061 parts and looking forward to building something up to see what I can get out of them - I have been using your web page as a reference, no sense re-inventing the wheel but I will put my own spin on it as well.

cheers, Graham in Embrun near Ottawa Canada

looks cool.
what steel alloy is machined from?
I like the shorty-ness.
Look forward to see`n the other bits.

J.M

It's nice to see that there's still enough intrest in the small burners to find projects like this.

Mind you as the electric stuff takes over from the 1/2A engines with the mainstream it tends to filter out and leave behind the ol' codgers and truly passionate (fanatical?) of us.....

The Sharp edge thing, I go with the flat so I dont worry about cracking, I have found no rpm difference, but that is relative anyway.
The steel on this one is 8620 (oil quench) Very easy to machine in annealed state
I made another out of S7 steel. air hardening. I heard good results of it, The stuff is difficult to machine though in the annealed state.

As far as the material on the AP crank, I have no idea, THe norvel's measure 57-60 crc so I know their stuff is good. I never tempered them softer. (cant go harder)
I have no clue what material the norvel is either.
Having fun

Hmmm, that's pretty hard. I saw on your web site a picture of one of your Norvel engines and cranks where you relived the portion forward of the intake to reduce weight and surface area of the bearing surface. How did you do that? Grind it or use a carbide cutter?

cheers, Graham

I did that relief on a precision tool grinder called an "Ewag"
It is an exspensive machine (swiss) that is used to make carbide cutters, reamers, custom cutting tools. I bought a wheeel for it to cut high speed tools. I use that wheel to grind the cranks. The machine is at work, Wish I could afford one for the garage lol (about $150k)
I first tried cutting the Norvel cranks with carbide, didnt even touch it

Toad, is a cut off wheel that turns into the spinning work considered OK to make that cut?

Any thing that will remove the material is ok, the main thing is to not go below .220 in dia and DO NOT get the steel hot! If any part of the crank turns straw colored or blue while cutting, you can bet Rog's last dollar, that the crank will break in flight. (loss of temper/hardness of the crank, the metal turning colors means you are too late)
This mod to the engine will give an incredible increase in rpm all by it's self. If I were to use a cut off wheel in a dremel, I would chuck the crank in a drill press, lathe, or cordless drill, low rpm, and use alot of water and take your time so you dont heat it up.
The idea is weight removal and surface area relief for friction in the case. Make sure you leave about .150 at the front for bearing and make sure you dont relieve too much towards the opening for the carb, I mark the crank while in the case, through the ventrui, I draw a line on the crank where the front edge of the venturi window is. Take out the crank and stay .020 or so in front of your mark so you dont open the relief into the venturi passage.

Thanks for the detailed info. Does this kind of grinding tend to raise the metal any at the ends of the cut?

Yes. you have to make sure the corners are smoothed off when done, 240 wet/dry emery works good.

Did the increase in rpm come from the reduction of bearing area or from reduced weight (or a bit of both) ?

I was reading some old issues of Speed Times (the newsletter of the North American Speed Society control line stuff) and there was a note in one of the motor modification articles that you should demagnetize your crankshaft after you have finished working it over. Makes sense, any magnet in motion will induce a current in any nearby metal which in turn is power and in this case would be lost power as the rotating crank would have to overcome any back emf. A simple tape deck demagnetizer like those sold at Radio Shack should work.

I wonder how much difference it would actually make. It is one my list of things to try, magnetize a crank and then run a motor for a baseline, then demagnetize and run again within a half hour or so such that conditions dont't change much; and compar the results.

cheers, Graham

Well, by what Wayne Trivan did, he was a big advocate of turning less mass, check out his prop balancer, I did the same mods and wow that works, so I figgure the same principle works on any rotating part, less mass means less power to keep it spinning, more mass would help in the tourque game though. For my purposes, I like the rpm game, and the light crank by itself paid me back bigtime. In the norvel, I think it is a 50-50 deal between mass and friction relief.
I scrapped the case I was machining last night [] Doh!
I have been pondering the "perky" event along with 1/2a proto...too
I will post some pics on the new case I will start tonight for my 1/2a r/c pylon.....still devestated about scrapping the first one.. I did the age old mistake, mis-read the mic .100 and cut that baby....no way to put material back on. My heart fell to the floor, I had over 6hrs into it on the mill. Its kinda hard to do. second time shouldnt take so long though I hope.

I hate to say this, but it is reassuring to hear about it when a pro makes a goof. I thought I just had a case of adult onset retardation.

" I thought I just had a case of adult onset retardation. "
LMBAO
Nahhhhhhh its a result of Murphy's law, give that Irish bugger a chance n he'll stuff anything

Ya know, Ive made pistons before, cranks, sleeves, heads, and head buttons, This is my first try at making a case.
I didn't copy Wayne Trivins engine design, but I like his approach as in using a stub to machine from. That works great and really simplifies things , not as many special tools or jigs are needed if you do it like that. If you like a challenge, you gotta try this! I figure I will be lucky if I dont flub up another before I get one finished. It really makes you think about procedure and double checking your measurements.

Too bad about the case. I have not progressed that far yet using my simple tools (Taig lathe with milling attachment) I am amazed at what I have been able to do. The biggest challenge is figuring out how to hold something so you can machine it they way you need it.

As to the Perky event. I have been the one organizing the Perky Old Time Speed Postal event. There have been a couple of short articles in Brodaks Control Line World magainze. There seems to be a steady growing interest with some big names in control line speed playing along. For that matter there is growing interest in Old Time Speed flying as well. I have the plans for the Perky if you would like a set.

cheers, Graham

Yeah, carpenters measure twice, cut once. Easy. WE have to measure and measure and measure, agonize some and measure again. Then we cut and oh nooooooo !!! [X(][X(][X(]

Still, fun when it's done.

A hassle but can you take pics of each stage in the process?

Graham,

I've been dying to get the Perky plans. Also what's the website for the forum. Let me know where to send the funds for the plans and I'll get right on it.

Thanks,

Rick

I am slowly building the Mills 1.3 Diesel as per the plans in the first issue of the Model Engine Builder magazine. Have the crankcase, crankshaft and prop driver finished. I made the crankshaft from a grade 8 bolt using the bolt head for the crank end. I am new to this so don't know how it will work out. Larry

PM sent.

for reference as the topic has been brought up, the Perky group on Yahoo groups is at:

http://groups.yahoo.com/group/PerkyOTS/

cheers, Graham