Author Topic: RMC Type-B Engine Build  (Read 2533 times)

Offline Jasonb

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Re: RMC Type-B Engine Build
« Reply #30 on: December 28, 2019, 08:02:59 PM »
Thanks but the credit should go to the designer and pattern maker.

The main bed casting looks quite a challenge at first but each operation is listed out in the build instructions and was actually not too hard to do.

First item is to hold in the 4-jaw by the chucking spigot and turn the small pip on the end flat and drill a ctr hole. I added some balance weights in the form of a couple of vee blocks and a 15-30-60 block taped and wired on which enabled me to run at about 400rpm before the lathe wanted to start dancing down the workshop. Once the tailstock ctr is brought up for additional support the feet can be skimmed flat.



The next suggested thing is to bore the cylinder but I could sense a little bit of movement when facing the pip so did not want to do the bore like this, I think is was due to the chucking spigot being slightly larger at the far end so it could not be gripped really firmly. So I flipped the casting around and clamped it to the faceplate so that I could true up the end of the chucking spigot to give me something even to hold.



With the bore and cylinder head mating face now machined I brought up the tailstock again and took the slightest skim off the feet to make sure they were true to the completed bore as that would be my ref surface for what followed.



One advantage of the imported lathes with their flange mount is that the studs can quickly be removed from the backplate so the chuck can be clamped to the mill table which is how I held the casting to drill the holes for the feet, cylinder head and I also added two holes for 3mm dowel pins front to back as I decided not to use a machining plate and the dowels would help with lining things up.





So with two bits of 3mm drill rod in the holes resting against the side of a tee slot the casting was set up to machine the top of the bearing housing that takes the oval shaped name plate, I added an angle plate against the side to resist the force of the cutter as I did not want to bend or break the casting.





While setup like this I also cleaned up the top of the cylinder, the 80mm indexable mill allowing me to get close enough without the quill hitting the overhanging bearing housing.



The instructions suggest using a 1" CSK to chamfer the top of the cylinder but as I don't have one that big I just managed with a boring head and tool ground at 45degrees.



To be continued

Offline Jasonb

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Re: RMC Type-B Engine Build
« Reply #31 on: December 28, 2019, 08:11:41 PM »
with two drill bits poked into the feet holes resting on parallels the base was clamped to an angle plate, to locate the ctr line of the cylinder I turned up a close fitting plug and touched off each side of that, heights were easy enough touching off the angle plate.



The bearing housing could then be drilled and reamed 1/2", I added some aluminium packets at teh bottom to stop any deflection from drilling pressure.



The casting was then rotated 90deg and with pins in the dowel holes again lined up to do the exhaust and spark plug contact holes



Then rotated 180 degrees to drill and tap for the sparkplug



Finally two angle plates were cobbled together so the casting could be held at a suitable angle to drill and tap for a grub screw to retain the exhaust which has to fit between two of the sloping cooling fins.



just enough done for a trial assembly.




Offline awake

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Re: RMC Type-B Engine Build
« Reply #32 on: December 28, 2019, 09:21:33 PM »
Wonderful pictures and write up - great illustration of how to go about machining a complex casting!
Andy

Offline crueby

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Re: RMC Type-B Engine Build
« Reply #33 on: December 28, 2019, 09:32:32 PM »
Great job on the machining - that is quite a shape to figure out how to hold.
 :popcorn:

Offline Dave Otto

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Re: RMC Type-B Engine Build
« Reply #34 on: December 29, 2019, 01:21:53 AM »
Nice work Jason!

Dave

Offline Jasonb

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Re: RMC Type-B Engine Build
« Reply #35 on: January 03, 2020, 05:06:35 PM »
The drawings include details for a home made spark plug to suit the engine so I had a go at making one, well two actually as the extra can be used in the Type D when I get round to making that.

The body started out being turned on the end of some EN1A bar and then screwcut 1/4 x 32 UNEF as I only have a tap that size. The large picture makes it look rougher than it is.



Next over to the spin indexer to mill the 5/16 hex



A suitable female thread was tapped into the end of a bit of scrap so the body could be held to finish the top end.



The insulator is a length of 3mm glass tube which cut very easily with a diamond coated disc in the Dremel, I used the slowest speed to avoid heating the glass and then just twisted the glass in my fingers against the disc to chamfer off the sharp edges



The central electrode is a piece of 0.5mm tig welding electrode and the final part is a small brass cap with a groove to accept the wire clip. The electrode is trimmed to length after assembly.



The plugs are assembled using Loctite 380 "Black Max" adhesive. I could not get the plugs to work at first and it turned out that the adhesive had insulated the electrode from the brass cap, a quick spot of electrical solder on the end soon cured that problem and the engine ran better than with the standard length Rimfire plug that I had been using for initial testing.

Unlike a conventional plug the spark does not travel from the central electrode to the plug body but to a long screw that enters from the opposite side of the cylinder, plug gap is adjusted by turning this screw and securing with a locknut. At one time Nick did offer a disc of glass that coul dbe fitted to a modified cylinder head so you can tip the engine up when running to watch the spark and ignited fuel.


Offline propforward

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Re: RMC Type-B Engine Build
« Reply #36 on: January 03, 2020, 05:11:48 PM »
That's fantastic. That actually makes me want to clap my hands with excitment. Great fun!
Stuart

Offline gary.a.ayres

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Re: RMC Type-B Engine Build
« Reply #37 on: January 05, 2020, 12:06:16 AM »
Wow...

A most elegant casting - and it's in good hands with you.

 8)

Offline Jasonb

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Re: RMC Type-B Engine Build
« Reply #38 on: January 06, 2020, 07:16:36 PM »
I did not take many photos of the adjustable timing bracket. Below is the lever having had a 2BA thread put on the end it was slid out of the chuck to reduce most of it's length to 3/16" leaving a 1/4" collar for the contact.



After cutting off it was held the other way round and a decorative ball turned on the end. The collar is straight forward turning and milling and the brass cotter applies the friction to hold it in position but still allow easy movement to advance and retard the timing. I opted to use Corian as the insulators rather than the suggested materials.



The "hemi" cylinder head was turned from some cast iron and as I don't have the large diameter ball nose cutter suggested I first drilled to depth and then hand cut the shape.



It was then held the other face out in the soft jaws and the outer curve also shaped by hand turning with a flat ended tool.



Finally over to the mill to drill for the fixings



The fairly long piston can be turned from the chucking spigot that was cut off of the base casting but I chose to use some 25mm CI bar. After turning and cutting the groove for the quad ring it was held in a collet block to have assorted holes and notches cut which provide the porting for the Loyal cycle.





The engine is designed to run on a surface vapour fuel tank which is based on a 1/2 pint "Ball" jar, to increase the surface area a felt wick is fixed to the lid and sits down in the fuel. This is held together with a central screw that is drilled for the vapour and has a reduced diameter end for a fuel pipe, here the head of the screw is being slotted.



Some large brass washers are also needed, rather than slicing up good bar stock I had some old 1/8" brass door kick plates that were cut up and milled to thickness followed by drilling the central holes, a step drill saves the risk of a jobber drill snatching in the brass.



They were then rounded off in the lathe.



This is the finished vapour tank



And the inside showing the felt wick



Final finishing touches are a pulley to go on the other end of the crankshaft turned from the chucking piece



And the nicely etched nameplate. This also has two recessed pockets in it to hold oil and holes are drilled through this, the bearing housing and bearings to get the oil down to where it is needed.









Offline Jasonb

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Re: RMC Type-B Engine Build
« Reply #39 on: January 07, 2020, 08:23:26 PM »
So with all the parts made it was time for a trial. As I mentioned earlier the homemade plug did not work at first so I used a standard length (too short) Rimfire and I also had a job getting the Viton Quad ring so initially tried a nitrile  one which started to swell with the fuel/oil so I just ran without rings. It would not run that strongly or for long, not helped By the bloke who keeps playing with the carb and ignition timing!


After a few e-mails from Nick which gave me some pointers things have started to get better, this is it running with the home made plug and a Viton O ring which has got the compression back up. I will bite the bullet and pay the high postage to get a Viton Quad Ring from the US and also want to try one of Nicks buzz coils which should give a stronger spark than the S/S single spark CDI that I am using at the moment.

To start with the engine has the governor weight free to move and is running in Hit & miss mode then tightened up to run with throttle control via carb and ignition timing.


I'm undecided if I like this paint job or whether I should have stuck with the bare cast iron, this is Rustoleum "cast iron" but it's a bit light in colour and looks "flat" as in lifeless not the opposite to gloss. Skids are apple.










Offline Admiral_dk

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Re: RMC Type-B Engine Build
« Reply #40 on: January 07, 2020, 09:27:00 PM »
Looks nice Jason - but I will admit it is a very discreet colour, almost bland .... I do really like the plague (sp?)

Runs fine in the last video - is the last (throttled) bit of that, in four-stroke mode ?

Per

Offline crueby

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Re: RMC Type-B Engine Build
« Reply #41 on: January 07, 2020, 09:49:53 PM »
Very nicely done. The shapes really make for a distinctive engine - maybe a close but slightly darker color on the inside corners to pick out the shape, give it more depth? Like shadow lines.

Offline gary.a.ayres

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Re: RMC Type-B Engine Build
« Reply #42 on: January 07, 2020, 10:53:23 PM »
To my eye the colour works well - in the photos at least.

A damn handsome engine with an H.R. Giger 'Alien 3' feel to it.   ;)

Offline Jasonb

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Re: RMC Type-B Engine Build
« Reply #43 on: January 08, 2020, 07:34:28 AM »
It's effectively a two stroke but there are a few miss fires which make it sound more like a 4-stroke.

Chris that is exactly what I feel it is lacking, I did think of some colour washes to get shadow and maybe a bit of dry brushing for highlights and had also considered a product we can get here called "iron paste" which is a graphite and wax past that you scrub on and then buff so the high spots are brighter - used for cast iron fire surrounds etc. but was worried about both methods being affected by fuel and oil or reacting to fuel proof lacquer

Offline Roger B

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Re: RMC Type-B Engine Build
« Reply #44 on: January 10, 2020, 11:16:16 AM »
Excellent  :praise2:  :praise2:

How did you remove the (very well designed) chucking piece, with a bandsaw?

Is the red G clamp some form of quick adjustment design? I haven't seen one like that before  :headscratch:
Best regards

Roger