Internal Fire Museum of Power

Hi All,

I am in the process of buying a 1918 5hp Petter M Jellymould, and was wondering how many of these engines and the earlier flat head M types are still in existence.

The one I am buying is on it's original trolley, and has it's original galvanised water cooling tank. The engine is in good running order, but has been restored and has a few non-original spec parts, but is a lovely engine. I have attached a couple of photographs of the engine below for reference:









David Edgington has kindly dated the engine as 06/06/1918, having been built by engineer Watkins, and sold to Rowell & Sons. I believe Rowells & Sons are still farming in Spalding, Lincolnshire.

I would be pleased to hear from anyone else who has one of these old Petter M's as I have no idea how many still exist. I am guess not too many though?

Regards,

_________________
Kevin
Lowestoft, Suffolk

I have one of very similar date which came from the Green King brewery.

cheers
Roland

Hi Roland,

The Greene King Brewery isn't far away from where I live, so your engine was originally sold local to me.

Do you have any photographs of your engine? I would be pleased to see a some photo's of your magneto bracket and drive gears if possible. As I have previously said (by email) my engine has a Bosch ZE1 magneto fitted (non-original) on a home-made bracket. Due to the magneto being the opposite rotation to the factory magneto this has been fitted on the other side of the crankshaft. See the photographs below:













This photo shows the difference in height between the top of the original magneto bracket (bottom of wooden marker), and base of the Bosch ZE1 magneto. Measures around 10-15mm. However, the magneto drive gear is currently positioned a little off centre from the centreline of the crank, and the skew gear teeth on the mag and crank fully mesh, so perhaps there is sufficient tolerance here to make the Bosch ZE1 engage sufficiently when mounted on the original bracket?



My magneto bracket measures 2 5/8" long (measured perpendicular to the crankshaft), and 3.75" wide (measured parallel to the crankshaft). It has obviously been drilled at sometime for another magneto, but I assume the 4 no. larger holes are where the original magneto would have been mounted. Are you able to advise what magneto my engine is likely to have been originally fitted with? I assume a Thomson Bennett AC1 or AC1Z from your website?

I was hoping to change the direction of rotation of my Bosch magneto, and fit this onto the original magneto bracket, but it appears that the splindle of the Bosch mag would sit too high to allow the skew gears to fully mesh if installed this way! I assume the TB AC1 mag is shorter between the centreline of the spindle and the base of the mag? This is a shame as I thought I could have made this work by leaving the magneto rotation as it is, and refitting the crankshaft skew gear the other way round so that it would turn the mag the right way when mounted on the original mag bracket! I think this would have worked, but it appears the mag bracket is too high for the skew gears to fully engage if using the Bosch ZE1.

I look forward to hearing from you.

Regards,

_________________
Kevin
Lowestoft, Suffolk

I quite like the mod, was it done in it's working life or when it was restored? A little interesting bit to its history and quite a clever idea!

Cheers Steve

In my opinion its a horrendous and unecessary bodge probably done in "preservation".
The ZE1 is a straight swap for a T-B as practically all mags of that era were based on the preWW1 Bosch.
I suggest:
- remove the ZE1 and the plate bodged to its base
- see if it fits on the correct side (I have a suspicion that the mag mounting plate is a later BTH type), and if it does then
- consult Eric's excellent article in SEM on how to reverse a mag.

cheers
Roland

Looking at the bolts used, I think your right.

Cheers Steve

Without taking the Magneto off it's home-made bracket it seems pretty obvious that it isn't going to fit onto the original magneto bracket. The bracket is only 2 5/8" long (front to back), which is much shorter than the magneto base. Plus the fixing positions for the base of the Bosch do not appear to suit the holes in the magneto bracket fitted to my engine!

From my research elsewhere on the net I have a feeling my mag bracket may be the one used on earlier Petter M's fitted with the CAV magneto? I believe the T-B magneto bracket measures 3.5" front to back. Does that sound right?

So, my magneto bracket may be for the earlier CAV magneto which was fitted before my engine was originally sold (based on the info provided on Roland's website), so the mag bracket might not be an original part as Roland mentioned above!

I therefore believe I have two options going forward. I either need to get hold of a larger magneto bracket to suit my Bosch magneto, or find an older CAV magneto in working order and fit it to my existing magneto bracket. I guess this will depend on which part comes up for sale first! I would be pleased to hear from anyone with either a T-B Magneto bracket for a 5hp Petter M, or a single cylinder CAV magneto in working order.

Thanks for your help,

_________________
Kevin
Lowestoft, Suffolk

Can you please advise which issue of SEM Eric's article was published in? Alternatively, does the article exist anywhere on the net?

_________________
Kevin
Lowestoft, Suffolk

The BTH bracket is 2 3/4" so it might be a CAV bracket or an Imp or UH. The T-B bracket is 3"+. I cannot find my CAV to check.
I don't know what issue the article is in. Hopefully Eric will know and chip-in. Otherwise I can only suggest combing the annual indices as I would have to.
My J-M worked in the G-K Bury St. Edmunds cooperage until retired post WW2. It then cut firewood for a retired brewery engineer until I collected it about ten years ago. 600 mile round trip and a very long day!

cheers
Roland

Many thanks Roland, and thanks also for the BTH Magneto & T-B Magneto bracket dimensions for comparison with mine. If you could measure the base of your CAV magneto when you find it I would appreciate it.

Sounds like a you had a VERY long day collecting your J-M. 600 miles in a day is very good going, especially when you factor in hauling heavy iron around when loading and unloading! Do you have any photographs of your J-M that you can email or post on here? I would be pleased to see it.

All the best,

_________________
Kevin
Lowestoft, Suffolk

It takes any mention of my name on here to get my hand reaching for the mouse/keyboard!
Roland - I have had an article in preparation for some months ( on checking I see it is over a year...!) for SEM on the very subject you touched on, namely the similarities between Bosch/Simms magneto dimensions and those of UK-made "copies" during and post WW1. The article is based on an ancient and long-out-of print book named simply "Magnetos" by A.P. Young who eventually became Chief Engineer at BTH magneto division and I am reproducing the tables and diagrams to make them more relevant to stationary engines by omitting the multicylinder magnetos. Interesting thread, it all verifies what I have discovered - so now I suppose I must get on with this article. Meanwhile if anyone finds a copy of this book - BUY IT!
Eric

....Oh and by the way Kevin, I usually keep all the texts of all my SEM articles on CDs ( even floppies) so if you drop me an email ( see Helpline under Victoria) so that I have your email address to hand, I may be able to help - hopefully!
Eric

I have that book and it is very good. A few years back it went on e**y with a BiN of £10. I happened across it 10 minutes later
Yes the preWW1 Bosch magnetos became the de facto standard for taper and centre height. The basic style was widely copied by amongst others: Simms, Hills, T-B, and UH though the latter has a face cam with complex parallel motion points assembly. The CAV and Imp were very different visually but shared the essential taper and centre height.

cheers
Roland

From them pics if thats still at the sellers house thats where my victory model petter m came from..
Careful if you have a low step in your van as it will catch on his driveway..

Hi Jay, I bought the engine from Steve at Acle, Norfolk. His driveway to his workshop is quite steep, but didn't have a problem reversing our trailer in to collect it

Hope you're well and having fun playing with that nice big Bamford.

_________________
Kevin
Lowestoft, Suffolk