My Hodgson 9 Radial Final Assembly

[rythmnbls]

One of the finest examples of a Hodgson I have ever seen. The sound of the engine idling gave me goosebumps.

Congrats.

Steve.

 

[vihatch]

Your work is an inspiration to me as I work on completing the Howell V2. My ultimate goal model engine would be the Hodgson radial. Don't know if I will ever get there but it will be fun trying. Great job.

 

[keith5700]

Just had to say how nice this looks. There's some lovely engineering going on there. Seeing the video makes me want to make one for myself, especially hearing it with the headphones on! I'd love to see it with a big fat 3 blade prop.
Great job.
Keith.

 

[mu38&Bg#]

Congratulations!

Regarding the carb settings, does the engine run the same if you shut off the fuel pump and let it burn off the fuel in the bowl? The needle settings seem as though there is excessive fuel pressure. I assume the fuel bowl is vented to atmosphere? 1/2-3/4 turn is what I found is typical on glow RC engines converted to spark and gas. These carbs require the main needle to be set first at Wide Open Throttle, then the low speed at idle to achieve a reasonable idle and transition to high speed.

Greg

 

[mayhugh1]

Dieselpilot,
Yes, it seems to run the same when I shut the fuel pump off. My fuelpump just maintains a constant level of fuel in the external carb bowl, and returns excess fuel back to the tank through a return line; and so the carb shouldn't be seeing any fuel pressure. And, both the bowl and tank are vented to the atmosphere. When I shut down the engine for the day I kill the fuel pump so the engine will use up the fuel in the bowl. For the next 7 or 8 seconds the engine runs normally and then speeds up as it leans out just before dying. I was just getting ready to set up the high speed needle at w.o.t. and then come back and touch up the idle when I notice my distributor was loose and the timing was ATDC. I needed three hands to hold the distributor, work the throttle and adjust the needle so I just shut it down. I'm working on the timing linkage now and will try your suggestion for setting the needles when I get that worked out. - thanks, Terry

 

[RCW]

I am in awe of your workmanship.

--Bob

 

[swilliams]

Top notch job Terry, it really has turned out superb.

I haven't looked in at your thread for a little while, and boy have you put some great stuff in. I really appreciate the detailed analysis you have done of your ignition system and lots of great info about the fuel and carb etc. You have really created a great resource for those who have the journey in front of us, which is much appreciated.

Cheers
Steve

 

[kvom]

I always fee a bit down after getting an engine to run and making the video. Time to think about the next project!

 

[seagar]

Congratulations !!!!!! Wonderful workmanship ,beautiful result.

Ian(seagar)

 

[mayhugh1]

I made a few minor modifications to the engine since my last post. First, I've added a control so I can easily vary and hold the ignition timing. When the grub screw that I was using as a friction device for the distributor sheared, it allowed the distributor to freely rotate under the vibration of the engine and allowed the timing advance to wonder about uncontrolled. (The screw is still in the rear section of the engine and keeps the distributor from rising up vertically.) This rotating lever solves that problem and in addition has adjustable stops that currently limit the timing between 5 deg BTDC for starting and 35 deg BTDC for w.o.t. running. I came up a workable design that linked the timing to the throttle, but I decided at the last minute to keep the two separate until I better understand the engine's timing requirements.
The next addition was a start-up checklist that I've posted on the firewall and which I hope will help with any future senior moments. A day after completing the little storage rack for the #5 and #6 plugs, I started up the engine and noticed that although it had started very easily, the rhythmic idle sounded differently from what I had become accustomed to. I also noticed that the #5 and #6 exhausts were spitting raw fuel and; sure enough, I had forgotten to install the two lower plugs. I was more worried about was happening with the ignition as I hit the kill switch, though, as the spark had no where to go for those two cylinders. The ignition seemed to function normally after the incident and so either the coil arc'd internally or the output transistor clamped at its Vcb breakdown voltage without catastrophic damage. My next and hopefully final step will be to dial in the carb needle settings. This time I will first set the high speed needle at wot and then set the idle needle. - Terry

 

[metalmad]

That is just the Ducks Guts Buddy!!
Pete

 

[xjs]

Truly inspirational, Mr Mayhugh. Well done, and thank you. I have enjoyed and appreciated your detailed narrative, and share (what I hope is) your joy in the result.

 

[Flopearedmule]

Does anyone know how far off the timing would be in degrees on the slave rods if the spacing in not corrected on this engine? Also is there anywhere we can find what the correct hole positions would be to hit TDC every 40 degrees?
Just curious
Thanks

Nice job Terry!! The pictures you gave us in this thread are awesome!!

 

[stevehuckss396]

Does anyone know how far off the timing would be in degrees on the slave rods if the spacing in not corrected on this engine? Also is there anywhere we can find what the correct hole positions would be to hit TDC every 40 degrees?
Just curious
Thanks

Nice job Terry!! The pictures you gave us in this thread are awesome!!

I have done the calcs but it was some time ago. I have modeled the correct slave positions and found that the rods hit the bottom of the cylinders. Bottom line is unless you want to redesign you will get a fine running engine the way it is designed. I can provide all the details if you want. PM me with any questions.

 

[Flopearedmule]

I have done the calcs but it was some time ago. I have modeled the correct slave positions and found that the rods hit the bottom of the cylinders. Bottom line is unless you want to redesign you will get a fine running engine the way it is designed. I can provide all the details if you want. PM me with any questions.

Thanks Steve, I know it runs good.......I've seen quite a few on you tube. I was just being curious if anyone held a timing light on all the other cylinders to see where they were at.
Dennis

 

[mayhugh1]

Dennis,
Your question got my curiosity up, and so I used my SolidWorks simulation to try to measure the timing errors you asked about. There is also a small height error as well. That is, the pistons on the slave rods don't actually come up to the same height as piston #1 which is on the master rod. My simuation is built around my actual machined dimensions, and so these results will likely vary some from their theoretical values. The values below are listed as #N(xxx"/xx.xdeg) where xxx" is the height difference with respect to #1 at TDC, and xx.xdeg is the crank angle error with respect to nx40 deg.

#1(.000"/0deg)
#2(-.006"/3.9deg)
#3(-.014"/2.9deg)
#4(-.010"/3.6deg)
#5(-.010"/-5.2deg)
#6(-.001"/2.6deg)
#7(-.010"/-2.8deg)
#8(-.014"/-6.4deg)
#9(-.006"/-4.3deg)

As Steve said, for a model display engine the errors are really not important. It would suggest a minimum timing of 10 deg BTDC, though, as Hodgson recommends. If the locations of the slave rod pins were altered to attempt to correct the errors (there is really no room for this in the current design) you would then introduce errors into the valve opening and closing times with respect to TDC for each cylinder and compression differences between cylinders would now occur. I haven't thought this fully through but it seems like the distributor could be designed to correct for this as an academic exercise by altering the position of the trigger magnets and the locations of the HV towers. - Terry

 

[Flopearedmule]

I'm not seeing the valve timing difference. with the 4 lobes exactly 90 degrees apart, they should open cylinders every 20 degrees.??
I think it was the guy on 5bears that made his master rod compensated, but he used steel instead of aluminum for more strength. maybe it was somebody else????

thanks for posting how far off in degrees. I have always been curious how far off in degrees it would be.

 

[mayhugh1]

What I meant was if the location of the TDC's were changed, but the valve opening positions remained the same as set by the cam, then the valve open times relative to the new compensated TDC's would be altered. For example if the TDC of one cylinder was delayed by 5 deg and there was no change to the cam then the intake would effectively be open for 5 deg longer before TDC but after TDC it would close 5 deg sooner. - Terry

 

[mayhugh1]

I thought I would make a final post on this build/assembly to wrap things up. The engine has been running for about a month now and I have run about a full gallon of gas through it. The engine starts easily by hand nearly everytime I run it. I learned that the secret to easy hand starting is to adequately prime the engine by placing my thumb over the wide-open throttle intake and then rotating the prop four times to suck in fuel to the point that my thumb gets pretty wet. Then I close the throttle to about 1/4 open and slap the prop with my finger. My distributor cap is transparent and so I can see the location of the rotor when I am ready to start it. I found that the best place to start the engine is with the rotor pointing to cylinder #8 or so. This allows me to get 3 or 4 cylinders fired by my hand strike before the distributor reaches the bottom two cylinders which in my engine usually are a bit wet with oil after the engine sits for several days. I'm not detecting any misfires in any of the cylinders. The plug colors look good and are uniform except for cylinder #9 which is a bit more sooty than any of the others. I may swap in one of my completed spare cylinders into this location someday to see if it makes any difference. The plug insulators all have a nice tan color with my current carb settings, but all the ground electrodes are always sooty. I think this is because the relatively high mass of these electrodes sticking out of the plug shell is cooling the charge in this area and the electrode is not getting hot enough to burn off the fuel. I've run the engine in the dark looking for misfires in the distributor but can see none. What I did see, though, is the heat of the rotor arc was slightly carbonizing the lexan around the tower contacts and I've had to clean this out after the initial quart of gas was run through the engine. This erosion seems to have abated and I haven't had to clean out the cap a second time. I closed the oil loop several days after my last post and ran into a surprise. The engine would start OK but would die after 10 seconds or so. As it turned out the scavenger pump is a great crankcase ventilator. After increasing the size of the vent hole in my oil tank cap from .030" to .080" that problem was solved. My oil lines are transparent tygon tubing and so I can see the oil flowing into and out of the engine when it is running. The crankcase pressure pulses are very noticible in the return line. My over-size oil tank works as a nice phase separator and pretty much all the gasses in the scavenger line are dissipated from the oil before being returned to the pressure pump. I've been experimenting with a new (to me) product called Tru Fuel. It is sold by Lowe's and is intended for use in small engines which are may see long storage periods. It is supposed to be equivalent to 92 octane gas (no alcohol) and is formulated for a long shelf life. I've run about a quart of this in my radial and in my V-4. What I'm seeing on the V-4 is that after starting I don't need to get on the carb adjustments to find a new stable running point to keep the engine running optimally. After dialing in the carb on the radial it, too, always has started and run without messing with the carb adjustments and so I don't know if the fuel is helping it. But I'm pretty sure it is making a significant on the V-4.
For my next project I became inspired when I ran across this link:

http://picasaweb.google.com/18.cyl.radial.engine/HodgsonRadial18#

Studying these pictures it appears that the twin version of this engine is just two 9 cylinders mounted back-to-back. I'm thinking about trying my hand at merging two of these together to make a twin. The guy that did this posted enough pictures that I think I'm going to try build a CAD model of the crankcase and then see if I'm still interested enough to start making chips. - Terry

 

[metalmad]

All I can say is WOW!!
That is some piece of work.
Pete