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billybobbooth

towys 2dm story, and a few questions on running as a 1dm (emergency use)

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ok so I'm spending a huge amount of time and effort and money this year on towys national.

 

most of the work is to simplify the pipe work, fit a removable (very important to me) electric starter system (this has now let to more complicated but better starting, stopping system and fuel lines) put in oilers were it was all manual and backly neaten it up and help it run better.

 

so the story so far when I got towy from a mechanics / engine builders view (me) the engine ran that's the only way i could put it, she used oil, she spewed out so much oil the bilge pump pumped out oil, she clattered, her exhaust system was dismal for ever changing sizes, it had 0 oil where is should have oil, it had oil where it shouldn't, the oil pressure bounced im mean bounced all over the place and water pumping more water on the floor than in the engine, it's power was limited and was gutless. basic answer im very surprised it stayed running, till it slowly ate threw the gearbox, and to top it off it had half been turned into a rn.

 

so simple after a year and at i thought was a sensible time as was going on dock so had 6 weeks to fix I stripped all the engine down till it was affectivly a built but blank engine, no gearbox parts, no water pump, no oil lines, no sump, no water pipes, no exhaust. nothing just a blank engine. at this time it was also made to make most parts that could go wrong easy to buy off the shelf at hardware shops as the engine was built in imperial days these parts get harder to find so bits that can be have been changed to metric so if a bolt snaps, fuel or oil leaks I can go to the nearest shop a nearly guarantee they will have the parts I need.

 

the gearbox was rebuilt after finding it had eaten itself, on removal, this ment new custom gears made, replacement shaft parts and bearings it also had the drive system and reduction gears separated again.

 

the engine in my idea of simplifying the pipe work made an error in not putting the oil relieve valve back and putting 90+ psi of oil pressure threw every part of the engine, in turn this actually helped the national as oil ways that had been blocked from gunk now had oil flowing out of them every oil was perfectly clean after this, the engine got a full de grease inside and every part I could easly remove got a good internal clean I even get oil flowing to the gearbox unlike before, after replacing all the oil, water and fuel lines (except to the injectors another should have just done it) and removal of all the rn parts and return to national and a new even flow exhaust fitted towys national was far better, no leaks, good steady oil pressure, no knocks bangs clatters, ran far far better, not perfect but better.

 

now a few years on the next stage of work on the engine is being done, oil pipes shortened and new oil filter system, new cooling system that now allows the engine to stay warm in cold weather helping to keep the engine at a stable 60 oC all day long, this has had a huge help in running better as it keeps heat in the cylinders better. it's also having all the manual oil wicks and oil points changed to automatic drip systems but in keeping with the engines looks but very quickly able to swap back, ill admit that it's my design but is being done for me by Bob tidy who has helped masivly.

new electric starter system fitted again removable so isn't a permanent fixture like most this was I can retain the stock flywheel and still make the engine look like it's hand start only as its never been electric start I didn't want to make anything that couldn't easly be put back to a stock ish national. 

 

I've also devised a way of starting the national on 1 cylinder or both cylinders and the same for stopping, this has been done so it's both easy to hand start by both cylinders start but also electric start I can stage the compression to put less stress on the starter system. as well as remove play from parts that were badly worn.

 

after years of hate for this engine im now starting to enjoy it I would still have a big single but the twin is slowly winning me round dispite her problems but in no small way a huge help from many of you so thank you! it's really helped.

 

now my question can a 2dm be run as a 1dm safely in emergency? the only thing untill I devise a way i cant stop is the fuel injector from squirting unless I remove that pipe and get the fuel to the tank or removed the injector pump for that cylinder, but say I had a problem on a cylinder could you use it as a single pot say stuck on a river or whatever and can't just stop?

I know before when it would only run on 1 cylinder it ran but it was very reluctant to even pick up a few secs let aloan even move the boat but i wonder if this was the other cylinders compression working against it?

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The problem is the propellor law.  This says that the power required by the prop is roughly the cube of its rotating speed.   Ie if a prop needs 10 hp to do 500 rpm it will need 80 hp to do 1000 rpm.

So if you halve the power output by running on 1 cylinder there will now only be enough power for the prop to be able to go round a lot slower. If that speed is close to normal idling the engine will not be able to accelerate, or may stall.

Losing one cylinder will also more than halve the power output, because most of the losses have not been halved.  That just makes things worse.

 

I think you will find your pre-improvement position a good guide to what will happen if you try it.  Use an anchor for emergencies!

 

Certainly my Kelvin J2 will run on 1  cyl, if I open an injector drain, but it drops to about 150rpm tickover (normally 225) and accelerates very slowly if at all, with mucho black smoke and general complaining.  It ticks over on 1 fine though, which is great for refilling the governor when needed.

N

 

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Shortly after I had a 2DM restored professionally (years ago when I had money) the rocker arm (is that what its called?) on one cylinder seized. I went 8 miles on one cylinder and it had easily enough power but was spewing thick smoke and unburnt fuel from the exhaust chimney.  Expert cured it by inserting large screwdriver on the rocker spring and hitting it with a hammer saying "It'll free up with use"  and it soon did.

I'd love to see your removable electric start.  I once made one from an electric paint stirrer driven by my Honda 1.0

Can you send me a PM with your location?

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intresting mine will run on one but will nearly do idle but i wasn't sure if this was more down to the other cylinders compression working against it.

 

yes I see what you mean about the prop, but as mine will hardly idle on one I didn't know if it was just my engine or if they wernt designed to even try running on one, as some like jp were designed to at least start and semi run on 1.

 

it was more food for thought but also see if anyone else had ever run 2dm on 1 cylinder.

 

ill take more photos when back at the boat of all my running setup as its in the prosses of all being built, I'm just waiting on the machine shop for the starter ring gear to arrive back. with a 2kw starter it should all work ok, the design is so it should fit any rn or national and potentially any other engine with no ring gear on the flywheel and cost around 1000-1500 to have done mine so far has been £160 for all the parts and steel but not machine labour yet if it all comes in at under £400 as should ill be happy.

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Can we see some pictures when you've got it together?(Interested custodian of handstart-only RN).

 

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A  DM3 will also start and run on one cyl,, the issue is as  much about gearbox type, size of boat & that load..

 

mine would just move on one,,, very easy on 2 cyls and on 3 will pull most people backwards...

 

 guess simplest thing would be disconnect fuel pipe and insert a blacker into the fuel manifold,,, ditto decompression lever,,,, just unbolt..

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1 hour ago, Strads said:

A  DM3 will also start and run on one cyl,, the issue is as  much about gearbox type, size of boat & that load..

 

mine would just move on one,,, very easy on 2 cyls and on 3 will pull most people backwards...

 

 guess simplest thing would be disconnect fuel pipe and insert a blacker into the fuel manifold,,, ditto decompression lever,,,, just unbolt..

can't just blank it off as it will still try and build up pressure in the fuel, I'm going to try and make a spacer between the pump and fuel injector line that I can bypass the fuel into a small tank and then back into the fuel filter by adjusting a 3 way valve.

 

yes will take pics with all in place hopfully this weekend, (except starter)

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ok I said I would up load a video of work i was doing but given this site, i went to do it and it won't let me I'm currently uploading to YouTube so I can link it.

 

I have fitted and tested they system till what I thought was correct position (turns out for once I got it spot on) I then started the engine and then tested it, after I then did a video of it not running but you get an idea of what my system does then i took one running showing it running on 2 cylinders the 1 cylinder then back to 2 then shutting it down,

 

i had huge amounts of play before in the decompression system ive now removed nearly all this play.

 

you can't see in the video but the fuel injector returns now go into the old original fuel filter box and from there get filtered and then go back into the new fuel filter so unlike before it use to drain to a pot that if overflowed went into the engine tray it now gets reused and there is no pot to empty making it a fully closed system,

 

the rocker covers are not missing just removed but hoping to replace with another mod so it is still a waisted system but unlike the wicks ill be able to turn off at end of the day, the rn uses a feed from the main oil meaning it wastes your engine oil and requires top ups. mine will be like the oilers on a mill engine, beam engine or steam engine.

 

 

hope these work

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Got the videos to work on You Tube after little fiddling.

 

Nice tidy bit of engineering.

 

Can you start it on one cylinder, the switch the other in? And if so, is it any easier (perhaps I should have said"is it any less difficult?")?

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yes will start on 1 cylinder yes it's easyer but by hand a bit problematic at the mo as the leaver for single starting is on the flywheel end and opposite end to the starter handle but I'll be putting a bar threw beween the 2 heads (sim to the rn leavers) so you can start and kill it easy from both sides but it's setup in the way it is so you can still start by hand and kick both in, the electric start button will be near the flywheel end on the exhaust side so it's easy to reach both leavers. will also mean in emergency it dosnt matter which side your on you can kill both quickly with 1 leaver

Edited by billybobbooth

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i want to get it as easy as pos but done in a way it looks like it should be there or has the view of still only hand start.

 

I'm trying to do everything on the boat as easy and liveable as pos with modern tech but with appearance that nothing looks like it shouldn't be there, even the lights are all being hidden so there there but you have to look to find them.

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Looking forward to seeing it when it's done.

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