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Post by ridleycove on Apr 3, 2020 13:36:39 GMT -8
Still trying to get the proper layout for a RMH with bell to heat a 3-season camp with little insulation. Numbers say I need a 9" riser, so a straight RMH will have a footprint around 3x5 feet. If I use the sidewinder, I'll end up closer to 4x4 which I think will fit better in the given space.
Now I'm trying to see what the ideal location for the sidewinder riser port should be. And if it is really close to the back wall, do I add a sweep to the opposite side to encourage an easier flow? If that is a design improvement, what about a small sweep in "front" of the riser port?
I am trying to stay very close to the dimensions based on the riser CSA, but if I add directional sweeps into the firebox to help the flow, do I compensate for the loss of volume by widening/lengthening the main burn chamber?
I'm hoping to have some guidance on these ideas before I actually start the build. I realize that I won't get absolute answers, but given the depth of knowledge in this group, it's as close to perfect as I'm going to get!
Many thanks to all the experts, participants and observers here. RMH may not be considered "mainstream" here in the States, but I'm hoping we can make some inroads to the "just get a wood stove" mentality!
Stay safe and healthy.
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Post by josephcrawley on Apr 3, 2020 14:39:41 GMT -8
batchrocket.eu/en/designs#core6At this link you can download a sketchup of a 6 inch sidewinder system. Use the scale tool to increase to 9 inch and take the measurements for port location from that. You will not need to alter the firebox shape in any way for a sidewinder to work properly.
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Post by ridleycove on Apr 3, 2020 17:12:09 GMT -8
Thank you Joseph! I know that Peter and many others have done extensive research on most things RMH and have been trying to tune the operation with changes to the throat of the riser (trip wires, curved entries, etc.) I wondered if the location along the side of the firebox had been adjusted to increase the turbulence of the secondary air - either P-channel or Walker(?) port.
Also, any thoughts on brick built or cast refractory for the construction?
Any input is much appreciated.
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Post by peterberg on Apr 4, 2020 0:46:48 GMT -8
I wondered if the location along the side of the firebox had been adjusted to increase the turbulence of the secondary air - either P-channel or Walker(?) port. The first sidewinder experiments have been conducted by Adiel Shnior in Israel. He started to have the port flush with the rear wall, results were meager to put it mildly. As soon as he implemented the port away from the rear wall and centered in the riser results improved immensely. The sharp corners left and right of the port need to be there, this creates small eddies along the port's walls. In effect, the middle of the stream is moving with the highest velocity, the sides being slower. In theory this should promote the forming of the double vortex better than anything else. So, stick to the design, no rounding of corners, smoothing of edges and adding of sweeps if a smokeles burn is what you want. Even the back sweep on the riser's floor is probably working against the agressive mixing which is the crux of the design. Larger back sweeps resulted in poorer performance every time. Years ago some people rounded off every corner in order to ramp up velocity, a computer simulation showed this was the way forward to enormous air speed. This resulted in a core that wouldn't stop smoking whatever they tried to stop it, even begging didn't help. Higher velocity isn't the way forward, rather the contrary. Also, any thoughts on brick built or cast refractory for the construction? Bricks are easier for a one-off, building moulds and casting refractory is the better way for serial production. Also, a cast core need to be split up in several parts in order to avoid cracks. |
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Post by Jura on Apr 5, 2020 11:15:09 GMT -8
I'm hoping to have some guidance on these ideas before I actually start the build. I realize that I won't get absolute answers, but given the depth of knowledge in this group, it's as close to perfect as I'm going to get! AFAIR this topic helped me significantly with port and floor channel sizing of an 8" sidewinder. |
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vanu
New Member
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Post by vanu on Nov 13, 2020 20:08:37 GMT -8
Bricks are easier for a one-off, building moulds and casting refractory is the better way for serial production. Also, a cast core need to be split up in several parts in order to avoid cracks. Hi peterberg,
Thank you for all of the helpful guidance. Much appreciated for a newbie to RMHs.
We're considering casting the J-tube using refractory clay as a more cost-effective alternative to buying firebricks. How would you suggest splitting up the parts? i.e. where would you suggest having expansion joints in order to avoid cracking, and what kind of mortar would we use to seal them? Can cracks in the J-tube be patched or are they a more serious repair job?
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Post by Orange on Nov 14, 2020 2:43:09 GMT -8
firebrick splits (thickness 2-3cm) are also cost-effective
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Post by peterberg on Nov 14, 2020 3:17:12 GMT -8
Bricks are easier for a one-off, building moulds and casting refractory is the better way for serial production. Also, a cast core need to be split up in several parts in order to avoid cracks. We're considering casting the J-tube using refractory clay as a more cost-effective alternative to buying firebricks. Refractory clay on it's own isn't suitable for casting parts. In case you insist to cast the J-tube please use refractory castable, which is much more suitable to produce sturdy parts. |
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