John W Sanders II, Update Power Generator
Although going at a sedate pace due to the amount of work we have, we have been carrying out some of the preparatory work on turning our imported American fire truck, into a food truck.
On Board Power
The food truck was intended to be self sufficient, and as part of this it was intended to have on board power. There are a number of cabinets on the truck, but all were a bit tight for space to install a generator with a decent power output.
Eventually we happened on a Yanmar 25kva unit. At 3000rpm it would be a bit noisy so we were gonna need to put a bit of work into sound proofing, but with a minor alteration to the mounting feet, it slid in the rear compartment like it was made to measure.
Noise
We acquired a noise meter to get a baseline reading, and at 1 metre we were experiencing an average of 105dB. Ouch!
We added a layer of Tecsound, intended to act as a barrier and also prevent noise transmission through the steel canopy. Then added some 50mm thick noise block sheet, which was basically around 40mm of high density foam, then a layer of lead, then a 6mm layer of foam to decouple the panel from the wall. To avoid blocking the end panel air flow too much we used a thinner 35mm version.
The reading after this was an average of 85dB, which sound being a logarithmic scale actually means we have cut the perceived noise level to around a quarter of what it started. Good, but we ideally want it down by another 10dB, or half again.
Most of the apparent noise appears to be coming from a combination of the top box housing the exhaust silencer and underneath the truck. The air intake and exhaust are actually underneath so these are basically open vents into the box.
Next Step
We have two more actions to try and solve this. First we are having baffled outlets made to cover both the inlet and outlet vents. A layer of soundproofing on the underneath of the cabinet floor would probably help as well.
Secondly we intend to box in the silencer with sound proofing.
Stay tuned for an update on where we get it too.
To try and keep the truck looking like a fire engine, rather then a funfair truck, we have piped the exhaust from the generator to one of the water pipe outlets on the unit, it probably needs a removable elbow and vertical pipe fitting for when it is in use, as that will also cut the noise down, but on the road it looks stock.
As far as we can tell in the UK, this will be the first fire truck food truck, well, American fire truck, I have seen a British Green Goddess in use to serve food, and a couple of typical Dennis type engines.
