MBI AHC Diesel

[Jo]

Some of you who live over the pond will have heard of AHC (America’s Hobby Centre) for the rest of us it was founded in 1931 and was at one time one of the biggest names associated with Model Aircraft. Around 1945 they embarked on designing a new Diesel Engine called the AHC Diesel, which was originally designed by Bernie Winston. Though announced the project was never brought to market.

The project nearly made it into production as the company had made the dies and had cast 500 crankcases out of “slag” (a cheap material not of the highest quality). We still do not know why it never came to market but finally one crankcase dated Jan 24 1977 and the remains of the drawings arrived in the hands of Ron Chernich. Ron with help from Ken Croft and David Owen set about redesigning and drawing up the engine in CAD.

The boys had a few crank cases cast and Bert Striegler built the prototype engine. There were early plans to make this a production engine but it was not to be....The intent had been to split the project three ways with parts going to Australia, Canada and England.

I know that the Australian third is with Ron’s estate, I do not know of the where abouts of the Canadian parts but I know of the location of at least one of the crankcases from the English set: it is sitting on my Dining table 

Jo

P.S. The two variants “Red Racer and Black Magic” I have been told were caused by some of the Motor Boys having some fun   .

[Dave Otto]

Interesting history Jo; is this one next in line after the triples?

Dave

[Jo]

Interesting history Jo; is this one next in line after the triples?
Dave

Yes Dave that's the plan I need something simple after my Orphans and this cutie looks ideal, it will be my first ever Diesel 

The only down side is where this was supposed to be an international team build the crankcase machining is nearly finished. All that fun trying to work out how to hold the casting to machine each stage is already done 

I do have a few photo's of the crankcase being machined: just it is not my work 

Jo

[Jasonb]

Can't your supplier give you a virgin casting out of that box full?

Are you going for the jam jar tank or that plastic jobbie?

[Jo]

No they have all been machined now 

If I can find a suitable jar I would use it otherwise it will be a case of running the fuel line up onto the bottom of the carb  .

Jo

[Jasonb]

What size does it need to be? looks about 25-30mm based on the bore

[Jo]

25mm is the maximum for the fuel tank or it will hit the back of the crankcase cover 

Jo

[Jo]

Can't your supplier give you a virgin casting out of that box full?

That was around the turn of the Millennium, this is the remains of the UK casting sets and by all accounts there was orders for about 20 of them (clearly now only 19  )

Jo

[Jo]

I've been a little for a couple of days which has meant that it is best I lay off the triples just in case it goes wrong.

I find the best cure for any ills is to make swarf   

Jo

[Jo]

Having looked at the Orphans and found a feature that made me go  I decided a bit of easy swarf making was in order 

Did I mention never trust the drawings  the thread in the top of the crankcase was not 20mm 32tpi as shown on the drawing it was 26tpi and just under 19mm 

Having done that I felt much better and realised that the Orphan's feature was not what it seemed  I may go back to them now that I have practised cutting a 26tpi thread 

Jo

[Jasonb]

Was it the drawing that was wrong or had the previous builder deviated from what was on the drawing? Sounds a bit like somebody had a 3/4" x 26 tap handy

[Jo]

The UK casting hoarder supplier had a 3/4 26tpi tap to hand when he originally cut them. Luckily he did mention to check first as his memory was going

Jo

[Jo]

  No, no, no that square thread still looks tricky.....

Milling the ports in the liner was interesting  The liner is a bit twee as are the milling bits to mill the ports. I ended up having o pull the liner a fair bit out of the indexing head and providing tailstock support. The good news is that the holes seem to line up on the casting 

The Contra piston looks interesting (much more interesting than cutting two start threads  ) but I am not sure how you are supposed to hold it to hone the outside...maybe superglue 

Jo

[Jasonb]

Bore the end of the contra piston on the end of a piece of rod, hone to a tight fit and then part off simples

[Jo]

  Which means I need to get Smelly set up to hone the liner in the not too distant future.

Jo