Office of Steam Logo_1

Author Topic: Bengs Modellbau 'Karl'  (Read 8449 times)

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #15 on: April 22, 2020, 01:20:51 pm »
Managed to get a few hours in the workshop this week, but i am still waiting for a 10mm reamer so there is much i cannot do at present.

I did ream the main bearing holders and make the main bearing bushes which are now in place ready to line ream them.

In the mean time i have been moving on with some horrid fiddly bits, my eyesight is making this very hard going and i am not getting the quality i had hoped for, but it will work.

Govenor arm and lock out assy done.



Finished and fitted.



And my paint turned up, so i have the base painted.  i wanted to get this done so i can mount the rather flexible crankcase square on the base before reaming the main bearings to ensure everything is in good alignment.



Kind regards
Ade

Scorpion2nz

  • Full Member
  • ***
  • Posts: 680
Re: Bengs Modellbau 'Karl'
« Reply #16 on: April 22, 2020, 01:34:37 pm »
Making great progress .
Is this one of “ Blood sweat and tears “ projects ?

Blood for the colour.
Sweating for the fiddly bits
Tears for the eyesight gone west ? .

Cheers
Dennis

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #17 on: April 22, 2020, 05:15:39 pm »
haha Dennis, it does look kind of blood coloured doesn't it  ;D

Raphael

  • Full Member
  • ***
  • Posts: 491
  • Steam passionate and collector
  • Location: Saint-Mandé (France)
    • MYCP
Re: Bengs Modellbau 'Karl'
« Reply #18 on: April 23, 2020, 11:40:11 am »
Bonjour Ade,
My friend Max has just finished his one, he now has to adjust the timing and carburetion which are very sensitive:

You know now you objective  ;)
Raphaël, Membre du Modèle Yacht Club de Paris : http://mycparis.fr/
Membre de l'Offshore Club de Paris: http://site-ocparis.wifeo.com/
Youtube : https://www.youtube.com/rhavrane

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #19 on: April 23, 2020, 01:52:02 pm »
Bonjour Raphael,

Thank you for the video from your friend, this is very helpful and sets the bar high :)

Making the carburettor looks like a headache, your friend will find the sweet spot soon i hope.

Kind regards and thanks

Ade

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #20 on: April 25, 2020, 11:08:44 am »
Its Saturday, wife is at work, time to get some progress  ;D

Backtracking a bit, Thursday gave me a few hours spare workshop time, There was a spare electonic ignition from one of Jin's M90s on the shelf, better than the points and big coil supplied with the kit IMHO as the unit and battery can all be hidden in the base.  A mounting plate was needed to position the Hall effect sensor inside the crankcase and a magnet fitted to the crankweb. 

The 2k paint on the base was now dry, so time to mount the crankcase square on the base and line ream the main bearings, things were going well again :-) 



Next was the crank.  The crank webs are pre milled but top hat bushes need to be turned to increase the surface area of the soft soldered bond.



And this is where the good luck run stopped, everything fluxed and fitted together ready for soldering, heat applied and the solder flowed nicely on the brass parts but refused to flow onto the silver steel shaft, clearly time to stop for the day.

After work on Friday it was time to clean up the mess, the shaft was still straight and cleaned up pretty well and with many applications of flux in finally tinned with solder.  This time i had to assemble it hot, a piece at a time which was not easy, but got there in the end.  The crank was still reasonably straight even after drilling the webs and hammering in the roll pins to give it strength.

I forgot to take pictures of the crank nightmare, was too concentrated on trying to recover the the disaster. 



A few well plced hammer blows had the crank down to less than 1 thou runout.  Had to shim it to get the crankpin central to the bore (i measured with the main bearing inside out and machined 1mm too much off the collar... duh)

OK back to Saturday, crank was done, next were the timing gears, again the gears were pre made but bushes had to be turned to fit them on the shafts.  The camshaft has only one bush bearing and with the thrust of the cam was already wobbling, time for a mod! Needs a longer bush me thinks, but can't move the cam gear inwards as it hits the crank.  In the end i added 2mm on the inside of the bush and recessed the cam gear to sit 'over' the end of the bush so the gear was only 1mm further toward the crank.  The outside of the bush gained an additional 2mm and the cam follower fork on the inside opened up to slide over it.  This gave me an extra 4mm of bearing area.  The pic below shows the new and old bushes.



Recessed cam gear



Cam follower fork opened up to ride over the outer edge of extended bush



All went together nicely with no wobble this time  ;D



The govenor spool was turned and fitted



Next up are the flywheels, i rough turned them and painted, couple of days for the paint to go off and i can finish em off.



And that was a very enjoyable Saturday, time to get a shower and something to eat and off to pick Lena up from work.

Raphael

  • Full Member
  • ***
  • Posts: 491
  • Steam passionate and collector
  • Location: Saint-Mandé (France)
    • MYCP
Re: Bengs Modellbau 'Karl'
« Reply #21 on: April 25, 2020, 12:20:07 pm »
Bonjour Ade,

This kit is definitely intended for experienced builders and you are one of them, I envy you.

I know that my friend Max has encountered many difficulties and he has overcome them, as you do. I can't wait to see it work, the highlight of your work
Raphaël, Membre du Modèle Yacht Club de Paris : http://mycparis.fr/
Membre de l'Offshore Club de Paris: http://site-ocparis.wifeo.com/
Youtube : https://www.youtube.com/rhavrane

AirSpyder

  • Jr. Member
  • **
  • Posts: 279
Re: Bengs Modellbau 'Karl'
« Reply #22 on: April 25, 2020, 12:30:51 pm »
Great project and great progress, this is a joy to watch. :)

RedRyder

  • Administrator
  • Hero Member
  • *****
  • Posts: 4310
  • Location: Connecticut - USA
Re: Bengs Modellbau 'Karl'
« Reply #23 on: April 26, 2020, 10:06:25 am »
You are making great progress, Ade!

Your attention to detail really shows up nicely.

Gil

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #24 on: April 27, 2020, 03:04:06 am »
Sunday Blues...

The paint was dry on the flywheels so Sunday started with finish machining these.



And the govener arms



And the flywheel locking collets



And this is where is started to go a bit wrong.  The govenor side flywheel was nice and true when mounted, as is the PTO pully, but the other flywheel wasn't true, so i have to sleeve the centre bore and machine it again.



At least one is straight :-)



Ade


yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #25 on: April 28, 2020, 02:11:15 am »
Think i must have spent roughly 8 hours on the right hand flywheel, plugged the centre and re turned it so it ran true on the shaft, then as soon as the tapered collet was tightend it ran out of true again.  Didn't make any difference where it was positioned on the crank, so in the end i dressed the taper collet by hand with a fine file until the flywheel ran true 'enough' not be noticable.



So now the bottom end is complete, it all spins freely with no play.  Got to make an 'adjusted' govenor spool and trim the crank to length on the left side once some brass rod arrives from the suppliers.



A new cylinder liner from Bengs arrived the other day and this one was much better and has a good surface once honed.  I decided to change the design so the liner is trapped between the head and water jacket rather than the head and crankcase, so this liner was turned to just have a 4mm lip at the top for location.



Next to start on the water jacket and make a hopper.

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #26 on: May 02, 2020, 01:59:39 pm »
Hey it is Saturday again! time for some more Bengs engine fun for me :-)

There was some free time in the week which allowed me to machine a new governor spool, trim the crank and final fit the govenor side flywheel.  With this done the governor was finished off with the weights and spings made.





Here is the crude water hopper i made from two pieces of Aluminium angle, hopefully once the top is made and it is sanded to shape it will look a bit nicer.



I was torn whether to try to Aluminium solder the hopper to the water jacket or use some aircraft aluminium epoxy a friend gave me, in the end i went with the glue.  Keyed the surface and bonded the hopper to the jacket.



The Piston rings i ordered turned up so next step was to try and make the conrod and piston.  Making the big end halves on the lathe was OK but filing the flats on either side was a mare.  I filed one side close but the was not enough material to hold it in the vice to do the other side, after a bit of head scratching and some four letter words it ended up in the pillar drill vice and a dremel bit in the chuck as a makeshift mill.  That pillar drill has been a Godsend throughout this project.



Eventually the rod was done, and it was straight and a good tolerance on the bearings



The plans show the piston as a heavy old lump of brass screwed to a cast iron piston with no rings, obviously it works but it kinda made me feel queasy, so i set to work making a normal aluminium piston with the rings i bought, should be lighter and easier as the piston to bore tolerance is not so tight.
Piston went well, ring grooves machined, good fit in the bore, small end marked out.



Then came the hard bit, again i wished for a mill to hollow out the centre of the piston.



In the end (in desperation!) the slot was chain drilled and chewed out with a dremel, bit rough and ready but i have to make do here.  Piston done and a lovely fit in the bore and suprisingly parallel  ;D



Hopefully tomorrow i can get the cylinder head done...maybe  ;D

Thanks for following the rather long thread.

Ade

Nick

  • Administrator
  • Engineer
  • *****
  • Posts: 8116
  • Location: Minnesota, USA
Re: Bengs Modellbau 'Karl'
« Reply #27 on: May 02, 2020, 09:57:08 pm »
Great Progress  8)  Thank you for all the pictures and keeping us updated  :)
Nick

Scorpion2nz

  • Full Member
  • ***
  • Posts: 680
Re: Bengs Modellbau 'Karl'
« Reply #28 on: May 03, 2020, 12:35:29 am »
Looks like you are making better progress on your project than i am on mine
Keep up the good work
Cheers
Dennis

yozhek

  • Jr. Member
  • **
  • Posts: 210
  • Location: Somerset, England
Re: Bengs Modellbau 'Karl'
« Reply #29 on: May 03, 2020, 01:52:04 pm »
Sunday, this is the day things usually go wrong, but never the less the cylinder head needs to be done.

First job was to make a mod to the lathe so can mark out 90 degrees and 60 degrees



So far so good



So the head could get some cooling i machined a water channel (complete with chatter marks) and a cover to seal it





Still retains the dimensions in the plans but was a tight squeeze



The valve seats, ports and plug were a tight fit in the space of the 25mm bore





Well the head went without a hitch, i think this project is teaching me to work more precisely and less slap dash  ;D

The Aluminium glue had dried so next step was to rough sand the water hopper, make a centering sleeve and fit the head and cylinder assy together and drill the holes to mount it all on the crankcase



It ia actually looking like and engine for the first time



Everything fitted beautifully, the piston and rings fit well and make a nice crisp sound, the crank and rod do their job with no play or binding, feels like i'm getting somewhere now  ;D



Thanks for watching

Ade