Glow Plug Whippet?

[Alan Worland 1Participant @alanworland1]

Since visiting Ally Pally in Jan I have found myself with a set of Whippet castings and rather that use spark ignition as designed I am considering running it as a glow engine.

Has anybody built Hemmingways 'Whippet' engine and had it running as a glow plug unit?

Any hints and tips would be most welcome!

Alan

[Alan Worland 1Participant @alanworland1]

[Old SchoolParticipant @oldschool]

Alan

To the best of my knowledge most two stroke glowplug engines run on a methanol castor oil mix, I dont know about the four strokes. You will need to alter the compression to run on metnaol you need to am at a head volume including the area above the piston of about 0.8cc this will run fine. Plugs for four strokes are available but if you cannot source one then a hot plug would be the best option to keep the glow plug alight.

I have a two stroke Dooling 10cc racing engine originally spark ignition this runs very well as a glowplug engine but needs some nitromethane to make up for the lack of compression but in a model race car this only helps.

Olly

Edited By Old School on 06/03/2013 08:52:35

[JAParticipant @ja]

I have almost finished building a Whippet. You must think and think again before drilling anything. As John says the position of the cylinder head bolts are tight and I have spoken to one person who had to reduce the bore to 3/4" to get the bolts in. Likewise the water passages. You will find that two passages will pass into the combustion chamber if you drill them. Also check the spark plug/glow plug thread type before you tap the hole. For the spark plug it is 1/4" x 32. I decided this was an ME thread (Whitworth form) only to find much later the plug was UNF. Since then I have spent quite a bit of time making long reach sparking plugs with ME threads!

The castings I bought were horrible to machine and at least two were replaced by the part machined from stock.

JA

[Alan Worland 1Participant @alanworland1]

Thanks for your replies.

I haven't started to machine any parts yet but the castings I thought looked quite good – other than one with a bit missing!

Thanks for pointing out the possible probs with cylinder head fixings – I would have thought things like this should have been ironed out by now.

I have a 10cc ohv glow engine which runs on the mix you refer to swinging a surprisingly large prop at a seemingly low rpm which sounds well. I may investigate the compression ratio although as the Whippet is a side valve engine I dont suppose I will be able to get it up to the same figure.

Looks to be an interesting project!

Alan

[Alan Worland 1Participant @alanworland1]

Thats a great looking engine Gray – makes me want to get started!

I have no particular use in mind for it but a slow tick over would be a basic requirement and as the side valve design is somewhat limiting for compression ratio it will probably end up as a spark job.

The glow ohv engine I have has a very tight combustion chamber so I guess c/r is quite high, although it does tick over seeming nice and slow.

Alan

[Sub MandrelParticipant @submandrel]

What would be an 'ideal' compression ratio for a 'slow' glow plug side valve engine, one where reliable starting and running was more important than power?

I ask as my little Suffolk is making slow progress and I think I may remake the cylinder head as I fancy the c/r is too low beyond redemption by skimming its base.

Neil

[Sub MandrelParticipant @submandrel]

Wow!

Neil

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