Water pump hammer

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Water pump hammer

Post  Steve Traill on Fri 12 Sep 2008, 4:46 am

Because my water pump seems to make a lot of noise I decided to make & fit a bulb to act as a cushion whilst it's pumping. I notice that a lot of fullsize engines have them along with the stationary engines. It's a bit more to polish as well! Haven't steamed with it yet so time will tell if there is an improvement

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Problem solved

Post  Julia on Wed 25 Mar 2009, 9:54 am

I have also found that water hammer is a significant problem. If I have the pump on I daren't go above 3mph (i have a spedo) as there is such a loud thump, thump, thump from the pump. Old hands have told me that the ram is too big but there is no simple way to reduce the diameter of the ram as it has to contain the connecting rod.

Rather than reduce the diameter of the ram I figured I could achieve the same result by reducing the stroke of the pump. The existing eccentric gives a travel of 7/8" and I made a replacement eccentric with only 1/2" travel. I also put packing between the sleeve and strap so that the ram still makes it to the bottom of the bore as I was worried about trapping air etc.


The new eccentric is identical except the offset of the bore is reduced to 1/4"


The original eccentric alongside the replacement

Whilst I was at it I decided to fit a popper limit stop for the lower ball. If the lift is too much the ball has time to build up speed and come to a halt with a loud thump. I extended the thread in the lower chamber to its full depth and made a special button. Not only does this enable me to accurately set the ball lift it also ensure that the ball come down squarely onto the seat.


The new lower seat prior to assembly

I did the modification whilst laying up the engine for the winter. I have delayed positing until I had a chance to test the modification. I have just returned after passing my annual steam test and an enjoyable drive around the park. The good news it the modification works very well. Gone is the thump thump thump noise and overall the engine sounds much better. The pump more than keeps up with the boiler and I guess I had it on for just less than half the time. Engine can now be driven much faster without nasty noises. It is so much quieter that I have spotted a few "new" rattles to sort out.

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Re: Water pump hammer

Post  Steam Traction World on Tue 07 Apr 2009, 1:53 pm

Hi Julia

We sent out the batch II eccentrics a couple of weeks ago, so we just missed incorporating your modification. There's still time to do the mod to the pump iteself. Icidentally, we're investigating doing this as a lost wax casting this time.

Before doing the modification to your pump eccentric, could you not have opened the bypass slightly, so some water would go into the boiler and some returned to the tender?

Regards

Steve

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Re: Water pump hammer

Post  Julia on Wed 08 Apr 2009, 12:42 am

Steve
I had to avoid running the pump when on the road at more than 3 mph. Even with the bypass fully open I experienced bad hammer at higher speeds. The pump worked best at about 2 mph. This causes problems on the road if the convoy goes too fast. Perhaps I should have followed your chain engine!

You will have a chance to see the mod at Whisendine. On first steaming after the mod the difference was immediately noticeable even at slow tickover. Swiss sewing machine like.

I still have a problem with my top valve seat. It is so bably damaged that I am going to have to machine down about 2mm to get below the crater that the ball has made.


This damage occurred despite having a stop to limit the ball lift to D/4.

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Re: Water pump hammer

Post  northburrell on Wed 08 Apr 2009, 8:16 am

Steve could this be a problem on the 2" version ?? If so can you look at sorting it before we get the pump.. even a new eccentric would be good..

Thanks

Jo

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Re: Water pump hammer

Post  tef 20 on Wed 08 Apr 2009, 9:02 am

Julia where do i place my order for the new eccentric and new lower seat? Very Happy i havent got that far on the burrell yet so it would be good to change it now rather that later.

Cheers
Mark

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Re: Water pump hammer

Post  Steam Traction World on Wed 08 Apr 2009, 9:11 am

The 2" Burrell Water Pump has already been designed with ways of limiting the amount of ball lift as has the batch II 4" version. It's too late for the eccentrics but there's no reason why we couldn't do a new one if demand is sufficient.

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Steve

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Re: Water pump hammer

Post  northburrell on Wed 08 Apr 2009, 9:17 am

cool thanks for let me know about that Steve.

I would have thought that opening the bypass valve would have sorted it out..

cheers

Jo

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Re: Water pump hammer

Post  Julia on Wed 08 Apr 2009, 9:58 am

I think the problem goes back long before MW adopted the design for their product. I saw on another forum from a builder that had built much the same design from castings that the issue is caused by small passage ways in the pump, pipe & clacks. Their solution was to open up the bores and the problem went away. I think this is the real answer and explains why the pump still will thump when the bypass is open.

I may be wrong but I often suspect that my engine pumps a little water even with the bypass open.

Julia

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