Author Topic: Lauson LA build  (Read 29959 times)

Offline Roger B

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Re: Lauson LA build
« Reply #165 on: July 11, 2018, 08:32:07 PM »
Catching up with this build again. Excellent work and looks almost ready to start  :praise2:  :praise2:  :wine1:

I was looking back at your points setup and wonder if your closed (dwell) time is too short. The points need to close for enough time for the magnetic field to build up in the coil. I think there is also a video missing in post 137  :headscratch:
Best regards

Roger

Offline Craig DeShong

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Re: Lauson LA build
« Reply #166 on: July 11, 2018, 10:17:06 PM »
Cletus, Kirk, Allen, Brian, Rodger, George: y’all are too kind; thank you for your complements.

Well, it runs: sort-of  :o
<a href="https://www.youtube.com/watch?v=YGroYtMSdm4" target="_blank">http://www.youtube.com/watch?v=YGroYtMSdm4</a>

The above is an edited video of the more successful (fits and starts).  I still have a few issues to address (like getting it to run dependably and the gas pouring out of the carburetor) but I’m thinking my remaining issues are confined to carburetion.  I’ve come across LOTS of problems in the last week or two, trying to coach some life out of this thing.

This little guy has proven to be one of the more problematic models I’ve built.  I will occasionally build a model (like the Debolt Star) that ran great the first time I cranked it over; but not this little guy.

I would never call myself an “expert” model engine builder, :Lol: there are some folks on this site that work at a caliber of which I can only dream of aspiring to; but I have built four of these ½ size Lausons.  The previous three run pretty well and I have no doubt that this one will too once I get the few remaining problems solved.  I’m going to document the highlights of the problems I’ve dealt with over the past two weeks so that some of the less experienced guys on this site can see that even someone who you would think ought to know what he is doing by now still can create a raft of problems to sort through.

My first problem occurred pretty early, like when I first turned this engine over with the starter.  You might remember that this engine, like the full size, has a mandrel threaded into the front of the block.  The hollow camshaft rides on this mandrel.  When I spun the engine with the starter, the cam mandrel, even though it had a locking nut on the outside of the block, promptly screwed out of the engine block and fell into the crankcase, taking the camshaft with it. :o   Drilling the locking nut (effectively turning it into a castle nut) and placing a keeper through the hole corrected that problem.

The second problem was that even though I had checked this earlier, the inside of the flywheel was dragging on something on the magneto.  I ended up using marker dye and spinning the flywheel, then disassembling to see where the problem occurred.  Fortunately, there was a little extra “meat” on the flywheel at the offending spot to remove and correct this problem.

Thirdly, the exhaust valve was leaking.  It wasn’t when I lapped and tested the valves but it sure was now.  More lapping and a stronger spring corrected that problem.

Fourthly, and Rodger had scoped this out up thread, but after I found it; I had spark at hand cranking speed but no spark when spun with the electric starter.  As Rodger suggested I increased the dwell time and corrected this problem.

Fifthly, the timing seemed to have shifted a bit to the “late” side, maybe due to “Four” above.  This was a mystery and since the timing collar had no adjustment (just like the original) I ended up redesigning the timing collar so that the timing could be adjusted; then re-timed the engine.

Now about a week had passed, and I had as yet to hear one solitary “POP” from this thing.

In frustration I removed the carburetor and squirted a little gas into the intake valve area, spun the engine, and POP POP POP three good successive fires. :ThumbsUp:  An inspection of the intake manifold showed it was completely blocked. :noidea:  Well, I had glued the five parts that make it up together, hadn’t I checked to see if it was blocked?  Apparently I had not.  I managed to fish out the blockage with a bit of stiff wire.

After that things improved dramatically and I thought I’d make this video to show it probably will run once the remaining kinks are worked out.

At this venture it seems to be starving out as it runs, but opening the main needle seems to flood it out.  With the construction of the needle, anything over three turns probably won’t make any difference. It either wants a VERY critical needle setting or I have some porting wrong in the carburetor.  I’m thinking more toward the latter and I’ll have my thinking cap on over the next few days about addressing that.  I also need to figure out from where the gas is pouring out of the carburetor; probably the float valve needs some attention and if this is the case, fixing this will probably correct the flooding problem; this has been a critical issue with the other carburetors I’ve built.
 
Then of course, in concert with getting it running better, there are lots of items to address to complete this model: the blower housing, fuel tank, and kick start mechanism to name a few.

All in all Cletus, time to sit back and open a beer to celebrate.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline Admiral_dk

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Re: Lauson LA build
« Reply #167 on: July 12, 2018, 10:51:36 AM »
Congratulations on a fine (if not completed) runner  :cheers:

I feel confident that you will iron out the last problems too  :ThumbsUp:

Offline gbritnell

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Re: Lauson LA build
« Reply #168 on: July 12, 2018, 11:55:55 AM »
Craig,
Congratulations to this point are certainly in order. From your explanations let me offer you my two cents worth. First I don't think the porting is an issue. I have engines with porting of all different sizes and shapes and as much as you'd think there would be a problem, there's not.
Carburetors in these sizes can be very sensitive so that could might be an issue.
The thing I'm suspecting is the ignition timing. It's hard to know exactly where to start. I usually begin between 10-15 degrees. Once the engine is running I adjust it to find the sweet spot. With your ignition timer buried that makes it more difficult. Once you get the carb sorted out I would play with the timing a little. It's amazing how just a couple of degrees will change the whole character of the engines performance.
gbritnell
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Offline kvom

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Re: Lauson LA build
« Reply #169 on: July 12, 2018, 04:02:05 PM »
Wondering why you've built 4 of these.  Addiction?   :shrug:  :noidea:

Offline Johnmcc69

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Re: Lauson LA build
« Reply #170 on: July 12, 2018, 06:35:02 PM »
Been following along silently Craig, but must say this is a beautiful build. Very well thought out & executed. Very nice work.

 Thanks for pointing out your trials & tribulations in getting the bugs worked out, good info to digest & as usual, great responses from the community here.

 Can't wait to see it finished & a family shot of the others with it.

  :ThumbsUp: :cheers: :popcorn:

 John

Offline Craig DeShong

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Re: Lauson LA build
« Reply #171 on: July 12, 2018, 10:05:00 PM »
Thanks for your encouragement, yesterday was a discouraging day. 

George- thanks for your advice. I’m going to look at the timing as you suggest but in post following this one you’ll see that my major problems were, chiefly, fuel related.  I might be able to tweak the timing some, resulting in the engine being able to run through abrupt throttle changes.  Any insight regarding that would be appreciated.

Kirk- I wasn’t clear regarding building Lauson models; I’m not building four of these things.  I have built three different Lauson engine models (this being the fourth) which I posted a while back:

http://www.modelenginemaker.com/index.php/topic,7500.0.html
http://www.modelenginemaker.com/index.php/topic,7501.0.html
http://www.modelenginemaker.com/index.php/topic,7502.0.html

Along with building models, I’m a Lauson small engine collector and over the years I have managed to collect nearly one example of each of the different types of air cooled engines that Lauson produced.  I maintain a website (http://lausonsmallengines.org) for use by other Lauson enthusiasts to assist them in their collecting and restoration of these engines.  I’ve been using a few of the engines from my collection as a basis for these models.   
« Last Edit: July 12, 2018, 10:27:44 PM by Craig DeShong »
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline Craig DeShong

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Re: Lauson LA build
« Reply #172 on: July 12, 2018, 10:25:38 PM »
A better day today.  I tracked the carburetor leak down to a blind passageway that hadn’t been plugged properly and once plugged the leak was stopped.  This also had the benefit of allowing the pressure differences in the carburetor passageways to work as designed and the result was a MUCH better running engine.
<a href="https://www.youtube.com/watch?v=z00VO20vuGI" target="_blank">http://www.youtube.com/watch?v=z00VO20vuGI</a>

I spent the morning working on a spring in the governor cap that allows the governor to regulate the speed of the engine.  I had limited success in this because abrupt throttle changes just seem to stall out the engine while it seems to tolerate slow changes pretty well; it actually has a decent idle when the throttle is closed slowly.  I’ll need to think on this a while, maybe Georges suggestion on tweaking the timing might address this and I’m open to other suggestions if anyone wants to volunteer any. :help:  I didn’t design/build an idle circuit in the carburetor so this doesn’t surprise me.

By noon I had pretty much killed my ignition battery and I was having intermittent problems with air getting in a siphon I was using to draw fuel from my temporary fuel tank.  I did manage to make this short video to redeem myself from the one I posted yesterday.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline Tennessee Whiskey

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Re: Lauson LA build
« Reply #173 on: July 12, 2018, 11:45:46 PM »
Now that just sounded so darn good that I’m going to drink a beer or three for you  :cheers:  :lolb:. Great job Craig.

Cletus

Offline zeeprogrammer

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Re: Lauson LA build
« Reply #174 on: July 13, 2018, 12:34:52 AM »
 :pinkelephant:

I'd been following along. Very happy to see your success.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline Craig DeShong

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Re: Lauson LA build
« Reply #175 on: July 24, 2018, 08:52:42 PM »
With this little Lauson running now, A few more issues have come up that need a resolution. 

Some of the J B Weld glue joints are releasing from the aluminum; especially in the kick start area.  This is area is saturated with crankcase oil and the oil appears to be working under the epoxy and lifting it; I’m thinking J B Weld probably isn’t the best material to use in this area.   

When I lessen the tension on the governor spring, the governor will close the throttle as the engine speeds up, just like it’s supposed to; unfortunately, when this happens the engine just cuts out.  I’m thinking this engine would benefit greatly from a low speed circuit designed into the carburetor.  This can be done, but it requires a carburetor re-design and re-fabrication.

I’m also being plagued by a points problem where, as the engine runs, the engine timing changes.  Some alteration of the points is probably in order.

Rather than just plow on with my first devised immediate solution to these problems, I’m going to set this project aside for a brief period while I think about the best way to address these problems; then after careful thought I’ll get back on this project.

Meanwhile, I have a few other projects that have been awaiting my attention far too long.
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline Craig DeShong

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Re: Lauson LA build
« Reply #176 on: July 23, 2019, 08:57:09 PM »
It’s been about a year since I’ve looked at this model.  It’s been sitting patiently on the shelf, awaiting completion.  Probably time to finish it.  I left it with a few problems and though it hasn’t seen any shop time recently, I have been thinking about it from time to time.

I’ve come to the conclusion that, as much as I’d wish, I’m not going to be able to get a scale magneto working on this model.  Also, the points I designed were slowly hammering out of time as the engine ran and by abandoning the idea of a functional magneto it was fairly easy to just install a set of NAPA points under the flywheel as you see below.


When I looked at the JB Weld glue joints they looked really sound so maybe a year of sitting has done them well.  I’m letting them alone and time will tell.

I’ve built a few other engines since I designed this one and I’ve come to the conclusion that my carburetion issue is that the carburetor throat (Bernoulli) is far too large for this model engine displacement.  At full throttle the carburetor can function but at lower RPMs there isn’t enough vacuum to draw fuel into the carburetor.  I’m going to decrease the size of the carburetor throat and see if this helps the idle.

So, with all these new decisions made, I’ve plowed ahead toward completing the construction.  First on the list was fabricating the PTO cover which I show here.


Next was addressing the kick start mechanism.  It’s going to be pretty cool trying to model this.  I need to fabricate five gears; three spur gears and two helical gears.  Here I’m using my dividing head to fabricate one of the spur gears.  All these gears will have a diametral pitch of 32.



Next are the helical gears.  To cut one of them I’m resurrecting Chuck Fellows helical gear cutter; the same device I used up thread to cut the crankshaft and cam shaft helical gears.  Chuck, hope you’re still with us to see your device getting more good use by a fellow modeler.  Thanks again for the effort you put in to assist many of us with your brilliance; and thanks to George Britnell for pointing me toward this solution.  Below I’ve just finished the gear (and yes, the beer is necessary for cutting helical gears, this is an instance where you definitely want to take your time and think things through in a leisurely fashion).   



I still have one more helical gear to cut.  With a pitch diameter of nearly 3 5/8th inch I’m not sure this helical gear cutter can accurately support the gear blank.  The good news is this is a fairly thin gear with 82 teeth (actually just a gear arc) so I’m thinking I can approximate the teeth with a straight cut with the involute gear cutter,  using a rotary table to position the gear blank.  More on this in a following post. 

Here are the various pieces and parts so far.



And here they are assembled to the engine

Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

Offline gbritnell

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Re: Lauson LA build
« Reply #177 on: July 24, 2019, 01:38:12 AM »
Great work on the helicals Craig! That set-up sure looks familiar.
gbritnell
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Offline b.lindsey

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Re: Lauson LA build
« Reply #178 on: July 24, 2019, 01:50:19 AM »
Nice to see it back on the front burner Craig.

Bill

Offline Craig DeShong

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Re: Lauson LA build
« Reply #179 on: July 29, 2019, 03:00:36 PM »
Thanks for your comments Bill and George.  Thanks also to those silently stopping by to see the progress.

Work has progressed on the kick start mechanism.  As I said up thread, I was very eager to tackle this because it’s one of the reasons I chose this engine to model.

In the last post I showed and described cutting the small helical gear.  In this post I tackled the larger helical gear.  This gear has a pitch diameter so large that I doubted if I could use Chuck Fellows handy-dandy helical gear cutter.  This gear is very thin: 3/16th inch and in design I made it a bit thinner than scale.  With the diameter so large and the teeth so narrow I thought I could cut it “like” a standard spur gear but with the teeth on a diagonal as shown below.



This turned out to work satisfactorily although, even at this width, the teeth did require a bit of filing to get them to mesh smoothly.  Here I show the finished gear or more accurately, gear arc.



With all the gears behind me I moved on to making the kick start bracket and petal.  The photo below shows the bracket and was a sort-of fun doo-dad to make and got me scratching my head a bit to work out the steps.



The petal was next and though I would have preferred to use aluminum to make the fabrication easier, there is quite a bit of stress and rubbing at the joint between the petal and bracket so I thought steel was a better choice.  Steel sure did make fabrication tougher though.  Below is a photo of the complete assembled mechanism on the engine.



Here is another view:



Finally, I give you a video of the mechanism in action.  I’m really pleased with how smoothly this operates.  At first I was thinking it might be for “looks” only but I’m thinking it might actually work well enough to be used to start the engine.  Time will tell.
<a href="https://www.youtube.com/watch?v=4s9ZeOqsiMQ" target="_blank">http://www.youtube.com/watch?v=4s9ZeOqsiMQ</a>
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.

 

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