Rina and T&K drawings

[Jim GreetheadParticipant @jimgreethead]

Aaah! Not you too Norman? John Somers (www.start-model-engineering.co.uk) gives me a hard time about the DVD player going backwards. We had a conversation one evening in which we each checked to see which way the water went down the plug hole. The result was inconclusive.

 

But I made him an Elmers Tiny upside down as a gift on one of my visits.

 

I like the phrase “abused the privilege” for tidying up after the glue has set. And I will also be more kind to the next one.

 

I don’t suppose there is any chance that I will see you at the Harrogate ME Exhibition?

 

Jim

 

[Jim GreetheadParticipant @jimgreethead]

Jeff: A question for you

 

Did you use standard roll pins like these?

 

http://www.smallparts.com.au/store/partslist/pinsrollplain/fasteners/wide/1/3.00/

 

Do you think these groove pins would be better?

 

http://www.smallparts.com.au/store/partslist/pinsgroove/fasteners/wide/1/3.000/

 

Sorry, that’s two questions

 

Jim

[Norman VantParticipant @normanvant32224]

Jim,

 

Under the circumstances it sounds a little lame to say that Suffolk to Harrogate is a long way for a day out but the aversion probably stems from 30-odd years doing a job that takes me away from home. The overriding aim is always to get back.

 

As for pins, when I need to pin something I normally use silver steel. It’s very handy ‘cos you can make the pin and the reamer from the same bar, pretty much guaranteeing the fit. Works beautifully for removable dowel pins. Otherwise, again, just a dab of Loctite. Honestly, I haven’t got shares.

 

Making the Rina body, I pinned as well as screwed the plates together so that it can be taken apart and I KNOW that it will go back in alignment. Same procedure on my beam engine where it was really vital to be able to reassemble with a positve register.

 

Regards,

 

Norman.

[Jeff DaymanParticipant @jeffdayman43397]

Hi Jim,

 

I used the standard roll pins, the exact ones I used are at this link:

 

http://www.mcmaster.com/#cadinlnord/92373a143/=fxgt6o

 

I wouldn’t use the groove pins as they will likely have higher drive force, and will not give a true line contact in the holes in both parts over their whole length, as the spring pins do. They will only make contact at one point, the bulge. The spring pins exert a constant pressure in the holes to hold them in place, as well, and ensure zero play between parts at all times.

 

You mentioned taper pins before. They do a good job with hole to location, and are very strong in shear, but I have seem many good machines destroyed because they worked loose and fell out. Also, special reamers are needed to fit them. The spring pins give excellent location also, have high shear strength, hold themselves in the hole, and the only tool needed for making holes for fitting them is a drill.

 

The spring pins are definitely my preferred method for this sort of job, and are cheap as well. Hope the info helps.

 

JD

[Norman VantParticipant @normanvant32224]

JD,

 

Seems like setbacks come in clusters. I had an email from the vendor of my coil to point out that it is for an AC supply. He has offered me a refund which I have accepted subject ot him not being able to offer something that would do. No reply, as yet.

 

It looks as if I have the pleasure of a trip to my local mower shop to see what they can offer. God help me!

 

The question occurs to me is that would small engine coils from there also be AC only, since strimmers and chainsaws don’t have a battery in the circuit? Getting a bit concerned now. Don’t want a full-size car one, it would look rediculously out of scale.

 

If these troubles go in threes, I don’t hold out much hope for tonight’s Council meeting!

 

 

Regards,

 

Norman.

[Jeff DaymanParticipant @jeffdayman43397]

Hi Norman,

 

Relax, first of all.

 

Second – try your coil in an ignition circuit with your planned battery or wall wart power supply, before sending it back or canceling your order. You will probably find it gives a spark on either AC or DC.

 

After all, an ignition coil is just a transformer. When the current falls off in the primary coil as the points (or a switch) opens, a high voltage spike is induced in the secondary which fires the plug. That’s all there is to it.

 

Yes, technically many small engines do produce an alternating current as the primary current. They do so using a magneto rather than a DC battery. Permanent magnets are mounted in the flywheel. As the magnets pass by the coil’s iron core the magnetic field is made and broken in the core to excite AC current in the primary wire coil. The system is constructed to have the points open at the point where + voltage is at peak. While the points are open and afterward, the coil voltage goes to zero and then goes briefly negative then back to zero as the magnets pass by the core ends. The important function is to produce the positive voltage just when it is needed, just before and at point opening. After that, primary positive voltage current is not needed in the coil. With a battery DC system, of course + voltage is always available, but again, it is only needed part of the time for ignition.

 

The basic ignition coil, as far as I know, is the same basic coil internal layout (of wire coils around an iron core) for car ignition coils running on 12 VDC or small engine ones running on (technically) AC magnetos.

 

I’m not an expert on this, but that is how I understand it, anyway, and have used these principles for many years to get engines to go bang and keep doing so. Suggest again you try your coil before taking other action. As to council – good luck.

 

JD

[Norman VantParticipant @normanvant32224]

JD,

 

Thanks for that. I have now declined the refund and asked them to dispatch the coil.

 

Your explanation has shed some light in a very dark corner. As you will have gathered, you are talking to an electronics basket case. I only managed to wire up my VFD because the instructions were completely idiot-proof.

 

Many thanks,

 

Norman.

[John OlsenParticipant @johnolsen79199]

Coils for different applications may have different turns ratios, but for a low speed engine like the Rina the choice of coil is not going to be very critical, and my own approach would be to try whatever comes to hand. If you can get a good fat spark out of it under test then it ought to be OK for the engine. If you get excessive sparking at the points increase the size of the condensor…that can be hard since the parts number probably doesn’t tell you the actual capacitance, so unless you have a digital multimeter that can measure them you don’t know what it actually is. Avoid ordinary electronics capacitors since they are generally not designed for this sort of service.It is not just the heat, the voltages are quite high and the sudden discharges and charges are hard on the dielectric.

 

Getting into the finer points….when the points close, current starts to build up in the coil. It will eventually reach a maximum determined by the resistance of the coil. Some coils are intended to be used with a ballast resistor, which limits the maximum current. If this is needed and not provided, the coil can cook up if the engine is left stopped with the points closed. You can check the current in this condition, and provide a resistance to limit the current if it seems too high…you should only need an amp or so. A 10 watt wirewound resistor would make a good ballast. If the coil is running off 12 volts and taking two amps, and you want it to take one, you would add a resistor equal to the coil resistance, which in that example would be 6 ohms. Some cars, eg MkII Cortina, used to switch out the ballast when the starter motor was cranking.

 

With multicylinder engines we used to worry about dwell, this is making sure the points are closed long enough to allow the current to build up to a sufficient value. This is not going to be critical on a slow running single like the Rina. Just make sure that the points open at the right moment. A waste spark on the exhaust stroke is not usually a problem although Triumph once had problems with engines which would fire on the much smaller spark that can occur when the points close. This was managing to fire the mixture near the beginning of the compression stroke. The engine then had to try to compress the burning mixture, which as you may imagine caused some overheating problems! The rider would notice that the engine had lost power and was getting very hot.

 

The coils that Honda used to use on their motorbikes would be good for a Rina, except that the twins and fours used double ended coils and so one from a single would be better. I don’t know what they use currently. These were fairly small and encapsulated in some sort of resin.

 

regards

John

[Norman VantParticipant @normanvant32224]

John,

 

That’s very encouraging. The coil I’ve ordered is for a small Honda single.

 

I remember the Ford ballast resistor. It was on a Ford 1600 engine that I first came across that. God knows, they needed all the help starting that they could get! Otherwise, all you got was the sound of duelling dusbin lids until all was silence.

 

Also amused by the Triumph tale. If mine was anything to go by, there was so much clatter that you couldn’t tell if anything else was wrong, though when the oil consumption exceed the petrol consumption it did give you a hint.

 

I’ve had my trio of disasters now and the only way is up.

 

 

Many thanks,

 

Norman,.

[John OlsenParticipant @johnolsen79199]

Yes, you could tell it was a Triumph twin when your back was turned. Mind you you could tell a Honda too…we always thought it was the cam chain that gave them a distinctive whine, but I think actually a large part of it was that they had straight cut primary gears, apart from the fours. (the 450 twin had two straight cut gears side by side, offset by half a tooth, an interesting approach to reduce the noise a little.)

 

The Mark II Cortinas also used to love to catch fire. They had a plastic fitting on the fuel line connection to the carby which would suddenly give up, so petrol would be sprayed at random around the engine compartment.

 

Oh well, getting a bit off topic for Rina.

 

regards

John

[Jim GreetheadParticipant @jimgreethead]

Nice to know that you are following John, off topic or not.

 

But as the owner of both a Tiriumph twin and a CB350, I can identify with your comments.

 

And going even further off topic, our Annual Rally starts today (I am riding the Triumph) and the weather forecast is for 28 degrees and chance of rain.

 

Jim

 

[John OlsenParticipant @johnolsen79199]

Hi Jim,

 

If you ever need to remove the alternator rotor from the crankshaft on the CB350, take out the back axle and screw it into the female thread on the alternator. Get it in moderately tight, then give it a tap inwards with a lead hammer. Keep tightening and tapping and the alternator should pop off the taper. This worked on all of the Hondas from the 60’s and early seventies that I got the chance to try it on, eg the singles and twins with permanent magnet alternators. They very kindly provide the puller in the form of the back axle. I can’t remember if I tried it on a CB350, I did help overhaul one once but that was only the top end, it had broken a cam chain and bent a few valves.

 

There is a 1961 Honda C95 Benly in the basement here. (150 twin with no centre main bearing and a 360 degree crank just like a Brit twin.) Well, not just like, it had unit construction, overhead cam, electric start, horizontally split case……Actually there is one togetnre and neary two more in pieces.

 

regards

John

[Jim GreetheadParticipant @jimgreethead]

Thank you John, now all I have to do is to remember that when (and hopefully if) I strip the engine down.

 

First up is the Triumph which started making very unhappy noises in the primary chain case. Luckily, I heard it before the chain emerged from its hiding place. So the Honda is getting a run.

 

Sorry Norman, that is getting further off topic.

 

Jim

 

[Norman VantParticipant @normanvant32224]

Jim,

 

No apology necessary. The off-topic bits make it interesting. Could do with a bit of interest whilst I’m re-making the crank.

 

More on-topic though, I suppose anyone interested in a model hit and miss will have see the You Tube below, but it’s still amusing. Beautifully made, but you couldn’t take it ANYWHERE!

 

http://www.youtube.co/watch?v=JDQmR6TngEU

 

Regards,

 

Norman.

[Jeff DaymanParticipant @jeffdayman43397]

Hi John and Jim,

 

Your comments on Honda CB350 bring back some great memories. I had a 1972 K4 model and once I rebuilt it from a basket case (the only way I could afford one) I loved it, and drove it for ten years, and sold it on at a profit! As far as I know it is still running.

 

Your back axle trick for alternator rotor removal is interesting. It wouldn’t have worked for mine though – someone before me had stripped the threads. I ended up sawing mine off (tears work great as a lube on aluminum) and replacing it. I had to get it off, as the starter clutch was behind it and was not working. The same joker who had stripped the rotor thread had put the flathead screws in without Loctite or peening and one had come out and smeared the whole assembly. Bits everwhere. Luckily I had a donor engine whose top end had disintegrated, so all the bottom end parts were OK.

 

Getting the slotted nut off the other side of the engine, inside the centrifugal oil “filter” slinger was interesting. I think I may still have the tool I made for that. It was a piece of steel pipe with four narrow pegs cut on one end like a castellated nut, and a tommy bar hole drilled at the other end.

 

A simple, light and very fast bike, pity they don’t make that style any more, and my back can’t take the modern “sport bike” leaning forward riding style. Occasionally I take a toot on my neighbour’s dirt bikes to keep a hand in the bike game.

 

Anyway enough OT, back to Norman’s Rina adventures. Any sign of a coil yet Norman?

[Norman VantParticipant @normanvant32224]

3 Js, hello again,

 

Back on topic with a vengeance. I’ve got the coil,and some points that should do. Trouble is, I’m back were I was a week ago. Rather too exactly.

 

I’ve made a new crankshaft. This one’s straight, glued and pinned. Also I’ve not cut the centre piece out yet in order to keep it as strong as I can, for as long as I can. A slight modiification of the old woodworkers’ saying. Here’s the rub though, the governor-side flywheel still wobbles when nutted up.

 

Investigation showed that whilst the bore of the FW is round and concentric with the rim, it’s been on and off so may times, the hole is a bit oversize. That wouldn’t be a problem but for the fact that I was using an upstand on the back of the drive key, pocketed into the back of the FW, as a positive stop. Naturally this only works on one side of the axis of the hub throwing the thing off true. I really hate wobbly flywheels. I know I’m an amateur but there’s no need to amateurish!

 

As a last gasp before packing up for the day, I tried an experiment with that end of the old shaft. I cut a groove and put an e-clip in it, then tightened the flywheel agains that.

 

Result: It runs completely true (on the experimental piece). No fun grooving into silver steel though. Next step is to do the same on the new shaft. There will be a very high pucker factor there. The stress of this is worse than working.

 

I’m going to take tomorrow off to get away from it and come back fresh on Monday. Well, sort of fresh.

 

Now get back toe the bike bodging stories.

 

 

Regards,

 

Norman.

[Norman VantParticipant @normanvant32224]

Jim,

 

I may be having a day off, but I’m still thinking.

 

I noted your earlier remarks about flywheel fixing and it seems to be a rather neglected area. Anything that takes up any clearance to one side or the other is bound to cause wobble. Most of the popular methods: tight keys; set screws; axial dowels etc., must fall into this trap. I suppose that’s the problem with building models – a couple of thou. shaft clearance on a 3ft flywheel would barely be noticeable but tolerances like that don’t scale well.

 

I have taken a look at the HMEM solutions. The tapered collet ones look very effective, if a little complicated, but don’t quite fit the bill for the Rina because the FW has to locate at a particular and repeatable position on the shaft, because of the governor settings.

 

It may be that the circlip and nut method will work. It did on the dummy. It certainly gives a dead stop for position. If it’s not 100%, I’m thinking along the lines of a simple split cone collet, bored shaft dia., pointy end inwards (corresponding taper in the outside end of the FW bore),with the blunt end protruding a little from the outer face of the boss. Tighten the nut with FW against the circlip at the back and it’s done.

 

Any flaws that you can see in that? My only misgiving is that I don’t really want to start hacking my finished, and labour intensive, carved-from-the-solid flywheels about. But it may come to that. It is something that I will consider from the outset in future. It would certainly make machining the flywheels on a mandrel a piece of cake.

 

Wobble isn’t cool!

 

 

Regards,

 

Norman.

[Jim GreetheadParticipant @jimgreethead]

Hi Norman,

 

I don’t have a clear picture of the way you are proposing to tighten the collet – will you thread the outside of the crankshaft, drill and tap the end of the crankshaft to take a screw (like a slitting saw arbor) or use screws through the collet into the flywheel?

 

As a result of my procrastination and faffing about, I have not started on the flywheels which are, as yet, disks of cast iron.

 

Because I rather like the look of solid flywheels, my intention is to simply bore them leaving the rim. And to provide a starting point, I will bore the hole for the crankshaft.

 

Since I was always going to bolt the bosses to the flywheel, it was a relatively simple exercise to design the bosses in two parts with a taper as shown in the photos uploaded to my Rino album. The ignition side has a driving dog to accept a starting bit rather like an old fashioned crank handle.

 

One other thing: I wonder if you really need the circlip or if a simple mark on the crankshaft would suffice. I suppose it depends on the way you tighten the collet.

 

BTW the weather was superb, the Honda survived the Rally and there was a beautiful Venom there that made me think of you. When the photos go up on the website, I will post a link.

 

Jim

 

[John OlsenParticipant @johnolsen79199]

I still have the magic tool for the Honda oil filter, mine was made for a CB100 but I know it fits a few other bikes as well. Dad made it for me out of a good piece of alloy steel. Apart from a valve spring compressor it is about the only special tool you need for one of those.I used to be able to get one out of the bike in half an hour and stripped down in another half an hour.

 

You should actually be able to get a flywheel to a pretty good fit on the shaft normally. I have seen a flywheel mounted on a tapered sleeve collet, the collet had a screw threaded extension on the small end that came right through the flywheel and a nut pulled it up tight.

I did the final trueing of the flywheel for my steam launch engine while it was mounted on the shaft with the engine running on compressed air.

 

I have one rather nice flywheel here, it was carved from solid and has curved spokes. It was done by a method described in one of the American comics. It really needs a mate, and then I would have no excuse not to build a slightly scaled up Rina for it.

 

regards

John

[Norman VantParticipant @normanvant32224]

Jim,

 

The new crankshaft has a 5/16 BSF thread on both ends. I have already made a starter dog nut for the governor side. My thinking is that if I made the collet with a saw cut down its length on one side (possibly beyond), that would give the necessary gripping action and if the outer, fat end protrudes a bit the nut should push it in and squeeze it closed.

 

I suppose the circlip would not be necessary if a piece of packing were inserted behind the FW during tightening to extablish position.

 

Now I have a thread at both ends, the same could apply at the other end too. However, since the circlip seems to work on my dummy, I think I’ll try that first. I really don’t want to have to set the FWs up for taper boring. Exact condentricity will not be easy. If that were to be done it should have been done in the first place at one setting. Hope the circlip groove doesn’t weaken the shaft too much.

 

This would all be relatively easy were it not for the governor bits behind the flywheel.

 

If the flywheels droop, I’ll tell people it’s down to old age.

 

 

Regards,

 

Norman.

[Norman VantParticipant @normanvant32224]

Jim,

 

As happens, life has intervened. I had to go to work bringing progress to a halt.

 

However, before I went away, I cut the circlip grooves on the crankshaft, fitted the clips and nutted up the flywheels. Guess what. They run true. It’s a bit of a tit to get the governor-side circlip in and out but the method works!

 

Now that I have come home, we seem to be in the grip of arctic weather. I would probably freeze to the machinery so no machning today.

 

I have just looked out of the window and I think I caught a glimpse of a polar bear snacking on a penguin.

 

Regards,

 

Norman.

[Anonymous]

Hmmm, either the polar bear or the penguin has made one hell of a navigational error! There are neither outside my window, but there are a lot of brass monkeys looking rather pained.

regards,

Andrew

[JasonBModerator @jasonb]

Get out there fast Andrew somethings may freeze off that are ideal for governor weights, pick em up quick.

 

J

[Norman VantParticipant @normanvant32224]

Andrew,

 

Haven’t you heard of globalisation?

 

 

Regards,

 

Norman.

[Anonymous]

Jason: What with the price of copper these days I’ll be straight down the scrapy; while they’re still paying cash.

 

Norman: Apparently not; clearly it hasn’t affected the ivory towers yet.

 

Regards,

 

Andrew

 

 

 

 

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