Jon James
Member
WOB,
Thank you for your advice.
Regards,
Jon
Thank you for your advice.
Regards,
Jon
Hodgson Radial - won't run
- Thread starter Jon James
- Start date
Help Support Home Model Engine Machinist Forum:
Jon,
So, are you using a Hall device for the trigger or are you using points?
Terry
So, are you using a Hall device for the trigger or are you using points?
Terry
Jon James
Member
Hi Terry,
Yes, I am using a Hall device from S/S, which is Roy Sholl.
In a previous post in this thread, Roy suggested a modified distributor cap, basically a cap with no sides so that the rotor and contact are actually visible. This should leave no unwanted path for the spark to follow. I am making that now.
If this doesn't help, it leads me to think it is a carb problem. A previous post in this thread suggests the Perry 4600 carb (recommended by Lee) is too big. He suggested a smaller Traxxas carb which I have on order.
As always thank you for your thoughts.
Jon
Yes, I am using a Hall device from S/S, which is Roy Sholl.
In a previous post in this thread, Roy suggested a modified distributor cap, basically a cap with no sides so that the rotor and contact are actually visible. This should leave no unwanted path for the spark to follow. I am making that now.
If this doesn't help, it leads me to think it is a carb problem. A previous post in this thread suggests the Perry 4600 carb (recommended by Lee) is too big. He suggested a smaller Traxxas carb which I have on order.
As always thank you for your thoughts.
Jon
Jon James
Member
My cap is Acetal from Mc Master. As I said earlier the spark passed right through the rotor to the shaft. So I bought some UHMW from them because the product detail said it had much higher dielectric strength and was an "excellent" insulator. So before I went to the work of making a new cap from the UHMW I did a similar experiment and the spark passed through it also. Crap!
So per Roy Sholl of S/S CDI ignition, I made a cap with no sides. Basically a Acetal plate 3/8" thick with the brass contacts protruding from the top and flush on the bottom. I supported it with 5 /8" standoffs. It sits about .010" above the rotor contact. I remade the rotor contact from a piece of printed circuit board about 3/16" wide, with a blob of solder to make the center contact. I glued the contact to the rotor, not screwed. Thus, the thickness of the PC board contact adds an extra layer of insulation. No where for the spark to go except where it should.
The rotor is visible from the side. I can actually see the rotor contact passing the contacts in the plate. I can see a ring of fire as it runs. Fun to watch.
Unfortunately, it still barely runs. Now I'm back to thinking carb. Awaiting arrival of a smaller Traxxas 4033 carb, as recommended in a previous reply. I hope that is it.
Jon
So per Roy Sholl of S/S CDI ignition, I made a cap with no sides. Basically a Acetal plate 3/8" thick with the brass contacts protruding from the top and flush on the bottom. I supported it with 5 /8" standoffs. It sits about .010" above the rotor contact. I remade the rotor contact from a piece of printed circuit board about 3/16" wide, with a blob of solder to make the center contact. I glued the contact to the rotor, not screwed. Thus, the thickness of the PC board contact adds an extra layer of insulation. No where for the spark to go except where it should.
The rotor is visible from the side. I can actually see the rotor contact passing the contacts in the plate. I can see a ring of fire as it runs. Fun to watch.
Unfortunately, it still barely runs. Now I'm back to thinking carb. Awaiting arrival of a smaller Traxxas 4033 carb, as recommended in a previous reply. I hope that is it.
Jon
Are you sure your fuel tank and crankcase are ventilated? The crankcase is best ventilated thru the scavenger pump with a small hole in the oil tank cap.
rsholl
Active Member
Jon, what fuel are you using? Lee's engine will run with the Perry 4600 carb. I'm not a big fan of Coleman fuel and last check on price looks like it is getting too expensive. My first go to fuel is 100LL av-gas if it is available in your area. I'm lazy and run my RC aircraft fuel which is E-85 mixed with Klotz oil at 32:1 (did I mention I was too lazy to mix fuel for the little engines so just use my regular RC mix). I have also done some running on the pre-mix sold for the chain saws and trimmers. I prefer the 40:1 mix and the best place so far has been TSC.
https://www.tractorsupply.com/tsc/product/trufuel-40:1-pre-mixed-fuel-32-oz?cm_vc=-10005
If you use the av-gas add one of the 1 gallon 2 cycle mixes to a gallon. Most brands are now using 50:1 which is fine. As for the carburetor, remember we are dealing with an alcohol (which is 3 times more dense than gasoline) design. I have not had the time to try and figure out what needle tapper would better suit the gasoline best but the needle setting will definitely need to be much leaner than what is stated for the Methanol fuel the carb was originally designed for. 40 or 50:1 will give you good top end lube and I'll guarantee it will not effect the operation or performance of any of our model gas engines. The Traxxas 4033 carb should work just fine too. It is almost impossible to put too small a carb on an engine and if you did, all it would do is limit the top end for speed. I believe the Perry 4600 is the same bore as the Super Tiger .60 size carb the guys were using when it was available. It will be good to know if the smaller Traxxas carb works better than the Perry 4600. Glad to see you are making good progress, keep it going.
https://www.tractorsupply.com/tsc/product/trufuel-40:1-pre-mixed-fuel-32-oz?cm_vc=-10005
If you use the av-gas add one of the 1 gallon 2 cycle mixes to a gallon. Most brands are now using 50:1 which is fine. As for the carburetor, remember we are dealing with an alcohol (which is 3 times more dense than gasoline) design. I have not had the time to try and figure out what needle tapper would better suit the gasoline best but the needle setting will definitely need to be much leaner than what is stated for the Methanol fuel the carb was originally designed for. 40 or 50:1 will give you good top end lube and I'll guarantee it will not effect the operation or performance of any of our model gas engines. The Traxxas 4033 carb should work just fine too. It is almost impossible to put too small a carb on an engine and if you did, all it would do is limit the top end for speed. I believe the Perry 4600 is the same bore as the Super Tiger .60 size carb the guys were using when it was available. It will be good to know if the smaller Traxxas carb works better than the Perry 4600. Glad to see you are making good progress, keep it going.
Jon, Like you said earlier, Terry's H9 build log is a great reference and I used it extensively in my build. When I was at your point in trying to get my engine to run, there are some comments from Swede in Terry's build log that for me were spot on. I'm sure you've read them, but his recommendations on carbs, carb setting, starting and oil management might be worth a revisit when you switch the carb. I think you are on the edge winning the battle.
John
John
Jon James
Member
Yes Terry. The crankcase is vented through the front of the crankshaft, and I verified it is open. For now, the scavenge is running open to a collection jar
Jon
Jon James
Member
Jon James
Member
Roy,
I have used AV100ll, regular pump gas and camp fuel. All with about the same result. The plugs that actually show ignition are usually black and sooty. The plugs that don't make ignition do show signs of fuel on them. I have the feeling I am not getting atomization of the fuel.
I made your "open" distributor design. I can clearly see the rotor and contacts and the spark from the rotor to the studs in the cap. As you said, nowhere else for to the spark to go. This also leads me to suspect carb..
Thanks again for all of your help.
Jon
Jon James
Member
Roy,
What should the clearance be between the Hall sensor and the magnets on your ignition?
Thanks,
Jon
Roy can chime in here if I'm wrong but I think it .040
Jon James
Member
Thanks Steve, that sounds about right.
Jon
rsholl
Active Member
Hi Jon,
Steve is correct on the .040" gap. Now that we ship the hall sensor in the plastic D-tube, the air gap is pretty much the thickness of the tube so the magnet would need to be very close. BTW, the hall sensor can be removed from the D-tube and oriented 180 degrees from the way my wife installs them. Just hold the D-tube and pull gently on the wire and the little wedge and sensor will come out of the tube. Since adding voltage clamping circuitry to my CDI and having the hall sensor mounted in the plastic D-tube, we have all but eliminated hall sensor failures.
Bottom line is, if the LED on the CDI unit comes on and goes off , the hall sensor is seeing the magnet. Speed is not an issue, if it works at slow hand rotation speed it will still work at max rpm.
Steve is correct on the .040" gap. Now that we ship the hall sensor in the plastic D-tube, the air gap is pretty much the thickness of the tube so the magnet would need to be very close. BTW, the hall sensor can be removed from the D-tube and oriented 180 degrees from the way my wife installs them. Just hold the D-tube and pull gently on the wire and the little wedge and sensor will come out of the tube. Since adding voltage clamping circuitry to my CDI and having the hall sensor mounted in the plastic D-tube, we have all but eliminated hall sensor failures.
Bottom line is, if the LED on the CDI unit comes on and goes off , the hall sensor is seeing the magnet. Speed is not an issue, if it works at slow hand rotation speed it will still work at max rpm.
Jon James
Member
Thanks, Roy.
